Syllacon NOTES BIOLOGY OUTLINE SINGAPORE-CAMBRIDGE GCE O-LEVEL SYLLABUS 5158

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1 Syllacon NOTES SINGAPORE-CAMBRIDGE GCE O-LEVEL BIOLOGY OUTLINE SYLLABUS 5158 UPDATED 20 JAN 2014

2 Overview Themes Chapters Count I. Principles of Biology II. Maintenance and Regulation of Life Processes III. Continuity of Life IV. Man and his Environment Cell Structure and Organisation Movement of Substances Biological Molecules Nutrition in Humans Nutrition in Plants Transport in Flowering Plants Transport in Humans Respiration in Humans Excretion in Humans Homeostasis Co-ordination and Response Reproduction Cell Division Molecular Genetics Inheritance Organisms and their Environment Note to student: Spot an error? Think that you can improve the outline? Download the.docx format of this document from the website and edit the outline yourself! Alternatively, you may wish to the site owner at lim.ting.jie.2012@vjc.sg with the subject title: Outline Feedback: O Level Biology Outline 2 Consylladated by Lim Ting Jie

3 Contents 1. Cell Structure and Organisation (a) identify cell structures (including organelles) of typical plant and animal cells from diagrams, photomicrographs and as seen under the light microscope using prepared slides and fresh material treated with an appropriate temporary staining technique: chloroplasts cell membrane cell wall cytoplasm cell vacuoles (large, sap-filled in plant cells, small, temporary in animal cells) nucleus (b) identify the following membrane systems and organelles from diagrams and electron micrographs: endoplasmic reticulum mitochondria Golgi body ribosomes (c) state the functions of the membrane systems and organelles identified above (d) compare the structure of typical animal and plant cells (e) state, in simple terms, the relationship between cell function and cell structure for the following: absorption root hair cells conduction and support xylem vessels transport of oxygen red blood cells (f) differentiate cell, tissue, organ and organ system Movement of Substances (a) define diffusion and discuss its importance in nutrient uptake and gaseous exchange in plants and humans (b) define osmosis and discuss the effects of osmosis on plant and animal tissues (c) define active transport and discuss its importance as an energy-consuming process by which substances are transported against a concentration gradient, as in ion uptake by root hairs and uptake of glucose by cells in the villi Biological Molecules (a) state the roles of water in living organisms (b) list the chemical elements which make up: carbohydrates fats proteins (c) describe and carry out tests for: starch (iodine in potassium iodide solution) reducing sugars (Benedict s solution) protein (biuret test) fats (ethanol emulsion) (d) state that large molecules are synthesised from smaller basic units: glycogen from glucose polypeptides and proteins from amino acids lipids such as fats from glycerol and fatty acids.. 20 (e) explain enzyme action in terms of the lock and key hypothesis (f) explain the mode of action of enzymes in terms of an active site, enzyme-substrate complex, lowering of activation energy and enzyme specificity (g) investigate and explain the effects of temperature and ph on the rate of enzyme catalysed reactions Nutrition in Humans (a) describe the functions of main regions of the alimentary canal and the associated organs: mouth, salivary glands, oesophagus, stomach, duodenum, pancreas, gall bladder, liver, ileum, colon, rectum, anus, in relation to ingestion, digestion, absorption, assimilation and egestion of food, as appropriate Consylladated by Lim Ting Jie

4 (b) describe peristalsis in terms of rhythmic wave-like contractions of the muscles to mix and propel the contents of the alimentary canal (c) describe digestion in the alimentary canal, the functions of a typical amylase, protease and lipase, listing the substrate and end-products (d) describe the structure of a villus and its role, including the role of capillaries and lacteals in absorption (e) state the function of the hepatic portal vein as the route taken by most of the food absorbed from the small intestine (f) state the role of the liver in: carbohydrate metabolism fat metabolism breakdown of red blood cells metabolism of amino acids and the formation of urea breakdown of alcohol (g) describe the effects of excessive consumption of alcohol: reduced self-control, depressant, effect on reaction times, damage to liver and social implications Nutrition in Plants (a) identify and label the cellular and tissue structure of a dicotyledonous leaf, as seen in transverse section under the microscope and describe the significance of these features in terms of their functions, such as the: distribution of chloroplasts in photosynthesis stomata and mesophyll cells in gaseous exchange vascular bundles in transport (b) state the equation, in words and symbols, for photosynthesis (c) describe the intake of carbon dioxide and water by plants (d) state that chlorophyll traps light energy and converts it into chemical energy for the formation of carbohydrates and their subsequent storage (e) investigate and discuss the effects of varying light intensity, carbon dioxide concentration and temperature on the rate of photosynthesis (e.g. in submerged aquatic plant) (f) discuss light intensity, carbon dioxide concentration and temperature as limiting factors on the rate of photosynthesis Transport in Flowering Plants (a) identify the positions and explain the functions of xylem vessels, phloem (sieve tube elements and companion cells) in sections of a herbaceous dicotyledonous leaf and stem, under the light microscope (b) relate the structure and functions of root hairs to their surface area, and to water and ion uptake (c) explain the movement of water between plant cells, and between them and the environment in terms of water potential (Calculations on water potential are not required) (d) outline the pathway by which water is transported from the roots to the leaves through the xylem vessels (e) define the term transpiration and explain that transpiration is a consequence of gaseous exchange in plants (f) describe and explain: the effects of variation of air movement, temperature, humidity and light intensity on transpiration rate how wilting occurs (g) define the term translocation as the transport of food in the phloem tissue and illustrate the process through translocation studies Transport in Humans Consylladated by Lim Ting Jie

5 (a) identify the main blood vessels to and from the heart, lungs, liver and kidney (b) state the role of blood in transport and defence red blood cells haemoglobin and oxygen transport plasma transport of blood cells, ions, soluble food substances, hormones, carbon dioxide, urea, vitamins, plasma proteins white blood cells phagocytosis, antibody formation and tissue rejection platelets fibrinogen to fibrin, causing clotting (c) list the different ABO blood groups and all possible combinations for the donor and recipient in blood transfusions (d) relate the structure of arteries, veins and capillaries to their functions (e) describe the transfer of materials between capillaries and tissue fluid (f) describe the structure and function of the heart in terms of muscular contraction and the working of valves (g) outline the cardiac cycle in terms of what happens during systole and diastole. (Histology of the heart muscle, names of nerves and transmitter substances are not required) (h) describe coronary heart disease in terms of the occlusion of coronary arteries and list the possible causes, such as diet, stress and smoking, stating the possible preventative measures44 8. Respiration in Humans (a) identify on diagrams and name the larynx, trachea, bronchi, bronchioles, alveoli and associated capillaries (b) state the characteristics of, and describe the role of, the exchange surface of the alveoli in gaseous exchange (c) describe the removal of carbon dioxide from the lungs, including the role of the carbonic anhydrase enzyme (d) describe the role of cilia, diaphragm, ribs and intercostal muscles in breathing (e) describe the effect of tobacco smoke and its major toxic components nicotine, tar and carbon monoxide, on health (f) define and state the equation, in words and symbols, for aerobic respiration in humans (g) define and state the equation, in words only, for anaerobic respiration in humans (h) describe the effect of lactic acid in muscles during exercise Excretion in Humans (a) define excretion and explain the importance of removing nitrogenous and other compounds from the body (b) outline the function of kidney tubules with reference to ultra-filtration and selective reabsorption in the production of urine (c) outline the role of anti-diuretic hormone (ADH) in the regulation of osmotic concentration (d) outline the mechanism of dialysis in the case of kidney failure Homeostasis (a) define homeostasis as the maintenance of a constant internal environment (b) explain the basic principles of homeostasis in terms of stimulus resulting from a change in the internal environment, a corrective mechanism and a negative feedback (c) identify on a diagram of the skin: hairs, sweat glands, temperature receptors, blood vessels and fatty tissue Consylladated by Lim Ting Jie

6 (d) describe the maintenance of a constant body temperature in humans in terms of insulation and the role of: temperature receptors in the skin, sweating, shivering, blood vessels near the skin surface and the co-ordinating role of the hypothalamus Co-ordination and Response (a) state the relationship between receptors, the central nervous system and the effectors (b) describe the gross structure of the eye as seen in front view and in horizontal section (c) state the principal functions of component parts of the eye in producing a focused image of near and distant objects on the retina (d) describe the pupil reflex in response to bright and dim light (e) state that the nervous system brain, spinal cord and nerves, serves to co-ordinate and regulate bodily functions (f) outline the functions of sensory neurones, relay neurones and motor neurones (g) discuss the function of the brain and spinal cord in producing a co-ordinated response as a result of a specific stimulus in a reflex action (h) define a hormone as a chemical substance, produced by a gland, carried by the blood, which alters the activity of one or more specific target organs and is then broken down by the liver (i) explain what is meant by an endocrine gland, with reference to the islets of Langerhans in the pancreas (j) state the role of the hormone adrenaline in boosting blood glucose levels and give examples of situations in which this may occur (k) explain how the blood glucose concentration is regulated by insulin and glucagon as a homeostatic mechanism (l) describe the signs, such as an increased blood glucose level and glucose in urine, and the treatment of diabetes mellitus using insulin Reproduction (a) define asexual reproduction as the process resulting in the production of genetically identical offspring from one parent (b) define sexual reproduction as the process involving the fusion of nuclei to form a zygote and the production of genetically dissimilar offspring (c) identify and draw, using a hand lens if necessary, the sepals, petals, stamens and carpels of one, locally available, named, insect-pollinated, dicotyledonous flower, and examine the pollen grains under a microscope (d) state the functions of the sepals, petals, anthers and carpels (e) use a hand lens to identify and describe the stamens and stigmas of one, locally available, named, wind-pollinated flower, and examine the pollen grains under a microscope (f) outline the process of pollination and distinguish between self-pollination and cross-pollination (g) compare, using fresh specimens, an insect-pollinated and a wind-pollinated flower (h) describe the growth of the pollen tube and its entry into the ovule followed by fertilisation (Production of endosperm and details of development are not required) Consylladated by Lim Ting Jie

7 (i) identify on diagrams of the male reproductive system and give the functions of: testes, scrotum, sperm ducts, prostate gland, urethra and penis (j) identify on diagrams of the female reproductive system and give the functions of: ovaries, oviducts, uterus, cervix and vagina (k) briefly describe the menstrual cycle with reference to the alternation of menstruation and ovulation, the natural variation in its length, and the fertile and infertile phases of the cycle with reference to the effects of progesterone and estrogen only (l) describe fertilisation and early development of the zygote simply in terms of the formation of a ball of cells which becomes implanted in the wall of the uterus (m) state the functions of the amniotic sac and the amniotic fluid (n) describe the function of the placenta and umbilical cord in relation to exchange of dissolved nutrients, gases and excretory products (Structural details are not required) (o) discuss the spread of human immunodeficiency virus (HIV) and methods by which it may be controlled Cell Division (a) state the importance of mitosis in growth, repair and asexual reproduction (b) explain the need for the production of genetically identical cells and fine control of replication (c) identify, with the aid of diagrams, the main stages of mitosis (e) identify, with the aid of diagrams, the main stages of meiosis (d) state what is meant by homologous pairs of chromosomes (f) define the terms haploid and diploid, and explain the need for a reduction division process prior to fertilisation in sexual reproduction (g) state how meiosis and fertilisation can lead to variation Molecular Genetics (a) outline the relationship between DNA, genes and chromosomes (b) state the structure of DNA in terms of the bases, sugar and phosphate groups found in each of their nucleotides (c) state the rule of complementary base pairing (d) state that DNA is used to carry the genetic code, which is used to synthesise specific polypeptides (details of transcription and translation are not required) (e) state that each gene is a sequence of nucleotides, as part of a DNA molecule (f) explain that genes may be transferred between cells. Reference should be made to the transfer of genes between organisms of the same or different species transgenic plants or animals (g) briefly explain how a gene that controls the production of human insulin can be inserted into bacterial DNA to produce human insulin in medical biotechnology (h) discuss the social and ethical implications of genetic engineering, with reference to a named example Inheritance Consylladated by Lim Ting Jie

8 (a) define a gene as a unit of inheritance and distinguish clearly between the terms gene and allele (b) explain the terms dominant, recessive, codominant, homozygous, heterozygous, phenotype and genotype (c) predict the results of simple crosses with expected ratios of 3:1 and 1:1, using the terms homozygous, heterozygous, F1 generation and F2 generation (d) explain why observed ratios often differ from expected ratios, especially when there are small numbers of progeny (e) use genetic diagrams to solve problems involving monohybrid inheritance. (Genetic diagrams involving autosomal linkage or epistasis are not required) (f) explain co-dominance and multiple alleles with reference to the inheritance of the ABO blood group phenotypes A, B, AB, O, gene alleles I A, I B and I O (g) describe the determination of sex in humans XX and XY chromosomes (h) describe mutation as a change in the structure of a gene, such as in sickle cell anaemia, or in the chromosome number, such as the 47 chromosomes in the condition known as Down syndrome (i) name radiation and chemicals as factors which may increase the rate of mutation (j) describe the difference between continuous and discontinuous variation and give examples of each (k) state that competition which arises from variation leads to differential survival of, and reproduction by, those organisms best fitted to the environment (l) give examples of environmental factors that act as forces of natural selection (m) explain the role of natural selection as a possible mechanism for evolution (n) give examples of artificial selection such as in the production of economically important plants and animals Organisms and their Environment (a) briefly describe the non-cyclical nature of energy flow (b) explain the terms producer, consumer and trophic level in the context of food chains and food webs (c) explain how energy losses occur along food chains, and discuss the efficiency of energy transfer between trophic levels (d) describe and interpret pyramids of numbers and biomass (e) describe how carbon is cycled within an ecosystem (f) evaluate the effects of: water pollution by sewage and by inorganic waste pollution due to insecticides including bioaccumulation up food chains and impact on top carnivores (g) outline the roles of microbes in sewage disposal as an example of environmental biotechnology (h) discuss reasons for conservation of species with reference to the maintenance of biodiversity, management of fisheries and management of timber production Consylladated by Lim Ting Jie

9 Overview THEME I: PRINCIPLES OF BIOLOGY A basic characteristic of life is the hierarchy of structural order within the organism. Robert Hooke ( ), one of the first scientists to use a microscope to examine pond water, cork and other things, was the first to refer to the cavities he saw in cork as "cells", Latin for chambers. Subsequent scientists developed Hooke s discovery of the cell into the Cell Theory on which modern Biology is built upon. The Cell Theory states that all organisms are composed of one or more cells, and that those cells have arisen from pre-existing cells. In this section, we study two key principles of biology. The first principle is the correlation of structure to function. This is illustrated by how each part of the cell is suited for its intended function. The second principle is that specialisation results in the division of labour which enables the cell to effectively carry out a number of vital life processes. A strong foundation in the principles of biology will pave the way for students to master the content in the subsequent topics. Extracted from BIOLOGY GCE ORDINARY LEVEL (2014) Syllabus Document 9 Consylladated by Lim Ting Jie

10 1. Cell Structure and Organisation syllacon.weebly.com Content Plant and Animal Cells Specialised Cells, Tissues and Organs Learning Outcomes: Candidates should be able to: (a) identify cell structures (including organelles) of typical plant and animal cells from diagrams, photomicrographs and as seen under the light microscope using prepared slides and fresh material treated with an appropriate temporary staining technique: chloroplasts cell membrane cell wall cytoplasm cell vacuoles (large, sap-filled in plant cells, small, temporary in animal cells) nucleus Cells Cells are the simplest units of life Each cell is made up of structures known as organelles for the cell to function # Structures Description Diagram 1 Chloroplast Ovular structure with a double membrane Made of grana (stacks of discs) containing chlorophyll linked by thylakoid membranes Found only in plant cells 2 Cell membrane Partially permeable membrane that surrounds the cytoplasm of the cell Refer to Diagram of an entire plant cell 3 Cell wall Fully permeable wall made of cellulose surrounding the cell membrane Found only in plant cells 4 Cytoplasm Jelly-like substance between the cell membrane and the nucleus Refer to Diagram of an entire plant cell Refer to Diagram of an entire plant cell 5 Cell vacuole Fluid-filled space enclosed by a membrane Refer to Diagram of an entire plant cell 6 Nucleus Spherical or ovular structure with a double membrane, usually found at the centre of the cell Made of a nucleolus (a smaller-sized spherical structure) and DNA in the form of chromatin 10 Consylladated by Lim Ting Jie

11 (b) identify the following membrane systems and organelles from diagrams and electron micrographs: endoplasmic reticulum mitochondria Golgi body ribosomes # Structures Description Diagram 7 Smooth endoplasmic reticulum 8 Rough endoplasmic reticulum Tubular network of flattened spaces lined by a membrane Connected to rough endoplasmic reticulum Does not have ribosomes attached to its outer membrane, unlike the rough endoplasmic reticiulum Tubular network of flattened spaces lined by a membrane Less tubular than smooth endoplasmic reticulum Connected to smooth endoplasmic reticulum Ribosomes are attached to its outer membrane, unlike the smooth endoplasmic reticiulum 9 Mitochondrion Small sausage-shaped structure surrounded by a double membrane The inner membrane is folded inwards 10 Golgi body Shaped like a disc Consists of a stack of flattened spaces surrounded by membranes Vesicles may fuse with or pinch off from the body 11 Ribosome Small round structure Either found attached to the rough endoplasmic reticulum or lies freely in the cytoplasm Diagram of an entire plant cell Note: Only study structures identified in the learning outcomes 11 Consylladated by Lim Ting Jie

12 (c) state the functions of the membrane systems and organelles identified above syllacon.weebly.com # Structures Functions 1 Chloroplast Absorbs sunlight to allow for the manufacture of food through photosynthesis 2 Cell membrane Controls substances that leave and enter the cell 3 Cell wall Gives the plant cell its fixed shape and protects it from injury 4 Cytoplasm Allows cell activities to take place using organelles present Catalyses biological reactions using enzymes present (e.g. breakdown of proteins into amino acids) 5 Cell vacuole Stores substances (e.g. water, mineral salts, amino acids) within cell 6 Nucleus Control all cell activities within the cell (e.g. cell division, repair of worn out parts) 7 Smooth endoplasmic reticulum 8 Rough endoplasmic reticulum Synthesises fats and steriods Detoxifies harmful substances (e.g. toxins) Transports proteins made by the cell ribosomes to the Golgi body for packaging 9 Mitochondrion Releases energy for cell activities (e.g. growth and reproduction) through aerobic respiration of food substances 10 Golgi body Stores, modifies and packages substances made by vesicles of the endoplasmic reticulum to be secreted out of the cell 11 Ribosome Manufactures proteins to be either used within the cell or transported out of the cell (d) compare the structure of typical animal and plant cells # Differences Animal cells Plant cells 1 Shape of cell Usually irregularly shaped Usually regularly shaped 2 Presence of chloroplasts Absent Present 3 Presence of cell wall Absent Present 4 Presence of centrioles Present Absent 5 Presence of vacuole Temporarily present Always present 6 Presence of sap Absent in vacuole Present in vacuole 7 Number of vacuoles Several Single 8 Size of vacuoles Small Large Additional information Sap contains various dissolved substances (e.g. sugars, mineral salts and amino acids) Centrioles are small hollow cylinders involved in cell division The table above only lists differences present. Remember to include some similarities too! 12 Consylladated by Lim Ting Jie

13 (e) state, in simple terms, the relationship between cell function and cell structure for the following: absorption root hair cells conduction and support xylem vessels transport of oxygen red blood cells Cell Function Adaptations Significance Root hair cell To absorb water and dissolved mineral salts from soil Long and narrow Cell sap present Increases surface area to volume ratio This allows rate of absorption of water and dissolved mineral salts from soil to be increased Cell sap has less water potential than soil This allows water to diffuse into the cell down a concentration gradient Cell membrane present Prevents sap leakage This maintains the abovementioned concentration gradient Mitochondria present Respires to release energy for the cell This allows active transport to occur if the cell has a higher concentration of ions and mineral salts than soil Xylem vessel To conduct water and dissolved mineral salts from the roots to the stem and leaves Lumen is long and hollow Cross walls and protoplasm absent Conducts water and dissolved mineral salts up the plant effectively Less obstructions enable water to flow more easily through the lumen This maintains a continuous flow To support the plant structure Walls are made of lignin Strengthens the walls of xylem vessels by providing mechanical support to the plant This prevents the walls from collapsing Red blood cell To transport oxygen from the lungs to all parts of the body Circular and biconcave shape Nucleus absent Increases surface area to volume ratio of the cell This allows oxygen can diffuse in and out of the entire cell at a faster rate Allows cell to carry more haemoglobin (since there is more space) This increases the rate at which oxygen is transported from the lungs to all parts of the body Able to change into a bell shape Decrease in diameter enables them to move through lumens (with small diameters) easily Also increases surface area to volume ratio to speed up oxygen exchange Additional information Protoplasm is made up of the cell membrane, cytoplasm and nucleus 13 Consylladated by Lim Ting Jie

14 (f) differentiate cell, tissue, organ and organ system Level Description Example Smallest Cells Cells are the simplest units of life Muscle cell Tissues Cells of the same type group together to form a tissue, which performs a specific function A muscle tissue is made of muscle cells Muscle tissues allow various parts of the body to move by contracting and relaxing Organs Different tissues group together to form an organ, which performs an overall function The stomach is made of muscular, glandular, connective and nervous tissues The various types of tissues work together so that the stomach can perform the overall function of storing, digesting and churning food Organ system Several organs working together for a common purpose form an organ system The digestive system is made of various organs (e.g. stomach, intestines) Largest Organism Various organ systems work together to make up the entire organism The human is made of various organ systems (e.g. digestive system, respiratory system) Use the knowledge gained in this section in new situations or to solve related problems 14 Consylladated by Lim Ting Jie

15 2. Movement of Substances syllacon.weebly.com Content Diffusion Osmosis Active Transport Learning Outcomes: Candidates should be able to: (a) define diffusion and discuss its importance in nutrient uptake and gaseous exchange in plants and humans Term Definition Diffusion Net movement of particles (i.e. atoms, ions or molecules) from a region where they are of higher concentration to a region where they are of lower concentration (i.e. down a concentration gradient) Importance Nutrient uptake Gaseous exchange In humans N.A. Oxygen from the air diffuses from the air sacs of lungs, where it is of higher concentration, into the red blood cells, where it is of lower concentration Likewise, carbon dioxide from the organism diffuses from the red blood cells, where it is of higher concentration, into the air sacs of lungs, where it is of lower concentration In plants Water and dissolved mineral salts diffuse via osmosis [will be discussed in the next learning outcome] from the soil, where it is of higher concentration, into the root hair cells, where it is of lower concentration Oxygen from the air diffuses from the soil, where it is of higher concentration, into the root hair cells, where it is of lower concentration Likewise, carbon dioxide from the organism diffuses from the root hair cells, where it is of higher concentration, into the soil, where it is of lower concentration 15 Consylladated by Lim Ting Jie

16 (b) define osmosis and discuss the effects of osmosis on plant and animal tissues syllacon.weebly.com Term Osmosis Water potential Definition Movement of water molecules from a solution of higher water potential to a solution of lower water potential through a partially permeable membrane Relative number of water molecules per unit volume of solution Measure of the tendency of water to move from one place to another Scenario If a partially permeable membrane is placed between a more dilute solution (more water molecules and less solute per unit volume) and a more concentrated solution (more solute and less water molecules per unit volume), water will move from the dilute solution to the concentration solution Effects of Entry of water No net movement of water Exit of water On animal cells On plant cells Effects of Entry of water (in dilute solution) Exit of water (in concentrated solution) On animal tissues On plant tissues Cells expand, swell and burst This is because no cell wall is present to prevent cells from bursting Tissue experiences loss of cells Cells enlarge and become turgid This is because the cell wall present prevents the cell from bursting Tissue experiences increase in turgor pressure Cells shrink in size and crenate (i.e. little spikes appear on the cell membrane) Tissue becomes flaccid Vacuole of cells shrink Cells plasmolyse (i.e. cytoplasm and cell membrane shrinks away from cell wall) Tissue becomes flaccid Additional information The verbal form of movement of particles via osmosis is also diffuse (i.e. there is no such thing as osmosises!) 16 Consylladated by Lim Ting Jie

17 (c) define active transport and discuss its importance as an energy-consuming process by which substances are transported against a concentration gradient, as in ion uptake by root hairs and uptake of glucose by cells in the villi Term Definition Active transport Process in which energy is used to move the particles of a substance from a region where they are of lower concentration to a region where they are of higher concentration (i.e. against a concentration gradient) Importance Ion uptake by root hairs Uptake of glucose by cells in the villi Case Description Only when root hair cells have a higher concentration of dissolved ions in water than soil Ions dissolved in water move via active transport from the soil, where it is of lower concentration, into the root hair cells, where it is of higher concentration Energy is consumed in the process Only when villi of the small intestine have a higher concentration of glucose than soil Glucose moves via active transport from the chyme of digested material that passes, where it is of lower concentration, into villi of the small intestine, where it is of higher concentration Energy is consumed in the process Use the knowledge gained in this section in new situations or to solve related problems Differences Diffusion Osmosis Active transport Particles moved Particles except water molecules Water molecules All particles Type of gradient Concentration Water potential Concentration Direction of transport Down gradient Down gradient Against gradient Energy consumption Absent Absent Present 17 Consylladated by Lim Ting Jie

18 3. Biological Molecules syllacon.weebly.com Content Water and Living Organisms Carbohydrates, Fats and Proteins Enzymes Learning Outcomes: Candidates should be able to: (a) state the roles of water in living organisms Organism type Animals Roles Digestive products can be transported from small intestine to body parts Waste products can be transported from tissue cells to excretory organs for removal Hormones can be transported from glands to requiring parts of the body Regulates body temperature (i.e. when water in sweat evaporates, latent heat of vapourisation is removed) Plants Photosynthesis Keeps plant upright (i.e. water keeps plant cells turgid and firm) Mineral salts can be transported up the xylem from the roots to the leaves Food substances can be transported from the leaves to other plant parts (b) list the chemical elements which make up: carbohydrates fats proteins Nutrient Carbohydrates Fats Proteins Carbon Present Present Present Hydrogen Present Present Present Oxygen Present Present Present Nitrogen Absent Absent Present Sulfur Absent Absent May be present 18 Consylladated by Lim Ting Jie

19 (c) describe and carry out tests for: starch (iodine in potassium iodide solution) reducing sugars (Benedict s solution) protein (biuret test) fats (ethanol emulsion) Biomolecule Test name Procedure Carbohydrates Fats Benedict s test Iodine test Ethanol emulsion test Benedict s solution is a solution containing blue copper (II) sulfate Add 2cm 3 of Benedict s solution to 2 cm 3 of the substance in a test tube Shake and leave the test tube in a beaker of boiling water for 5 minutes A green, yellow or brick-red precipitate (based on amount of reducing sugar) would be formed (i.e. traces, moderate amount and large amount of reducing sugar respectively) When a few drops of potassium iodide is added to a substance containing starch, the iodine solution will turn from brown to blue-black A cloudy white emulsion (i.e. a suspension of small drops of liquid in another liquid) is formed when ethanol and water are added to fats If tested on solid food, the food has to be cut up into many small pieces and added with 2cm 3 ethanol After shaking and allowing the solid particles to settle, decant the ethanol into another test tube with 2cm 3 of water, a cloudy white emulsion is formed if the food contains fat Proteins Biuret test Biuret solution is made up of sodium hydroxide and copper (II) sulfate When 2cm 3 of the substance is added and stirred with 2cm 3 of biuret solution, the solution turns from blue to violet if the substance contains protein 19 Consylladated by Lim Ting Jie

20 (d) state that large molecules are synthesised from smaller basic units: glycogen from glucose polypeptides and proteins from amino acids lipids such as fats from glycerol and fatty acids Large molecule Synthesis (enzyme not required) Carbohydrates Starch Many glucose molecules Maltose Many maltose molecules Starch Glycogen Many glucose molecules Glycogen Protein Many amino acids Polypeptides Many polypeptides Proteins Fat Glycerol + 3 Fatty acid Fat + 3 Water Large molecule Breakdown (enzyme required) Enzyme Starch Starch Many maltose molecules Amylase Maltose Many glucose molecules Maltase Protein Proteins Many polypeptides Pepsin (protease) Polypeptides Many amino acids Erepsin (protease) Fat Fat + 3 Water Glycerol + 3 Fatty acid Lipase (e) explain enzyme action in terms of the lock and key hypothesis Terms Definitions Relation to lock and key Enzyme Protein that speeds up the rate of a biological reaction Lock Substrates Substances on which enzymes act Key (that fits into the lock) Active site of enzyme Small portion of the enzyme that comes into direct contact with the substrates Groove (of the lock) Diagram Explanation The substrates have shapes that are complementary to the active site of the enzyme Thus the substrates are able to fit into the active site of enzyme This allows the reaction to take place This is similar to a key that is inserted into a lock, based on the lock and key hypothesis The key will only be able to open the lock if it is complementary in shape and fits into the grooves of the lock 20 Consylladated by Lim Ting Jie

21 (f) explain the mode of action of enzymes in terms of an active site, enzyme-substrate complex, lowering of activation energy and enzyme specificity Key question What are enzymes? What is the structure of enzymes that helps them achieve their role? How do enzymes achieve their role? Exam response An enzyme is a protein that speeds up the rate of a specific biological reaction Each enzyme has an active site, which is a small portion of the enzyme that comes into direct contact with the substrates Collision between substrates and enzyme at the correct orientation causes the substrate to bind to the enzyme at its active site to form an enzyme-substrate complex This increases the likelihood of bond breaking/forming, which lowers the activation energy of the reaction (the minimum energy needed to start the reaction) thus speeding up the rate of the reaction 21 Consylladated by Lim Ting Jie

22 (g) investigate and explain the effects of temperature and ph on the rate of enzyme catalysed reactions Term Denaturation Definition Random unlooping of the 3D structure of a protein or enzyme Factor Optimum level Effects of changes from optimum Diagram Temperature At optimum temperature, the enzyme is most active as high kinetic energy supplied causes more collisions between enzyme and substrate molecules and vibrations in protein atoms are not high enough to denature the enzyme As temperature decreases from optimum, As temperature increases from optimum, the kinetic energy supplied to the reacting molecules decreases This causes less frequent collisions between the substrate and enzyme molecules, decreasing the chance of substrates fitting into active sites Rate of formation of products thus decreases gradually vibrations in the atoms of the enzyme become more violent This breaks the hydrogen bonds of protein within the enzymes The enzyme loses its specific shape and denatures Rate of formation of products thus decreases steeply ph Some enzymes work best in slightly acidic solutions while others require slightly alkaline solutions Extreme changes in acidity or alkalinity of the solutions denature the enzymes The first reason is that hydrogen bonds of protein within the enzymes are broken The second reason is that most substrates and enzymes have opposite electrostatic charges that allow them to bind The extreme changes alter the charges on the substrate and enzymes such that they bind less well Use the knowledge gained in this section in new situations or to solve related problems 22 Consylladated by Lim Ting Jie

23 THEME II: MAINTENANCE AND REGULATION OF LIFE PROCESSES Overview Life is sustained through the integrated organisation of the whole organism. In humans, the maintenance and regulation of life processes include nutrition, transport, respiration, excretion, homeostasis and co-ordination and response. The key overarching theme in the study of the organ systems is the correlation between form and function. Extracted from BIOLOGY GCE ORDINARY LEVEL (2014) Syllabus Document 23 Consylladated by Lim Ting Jie

24 4. Nutrition in Humans syllacon.weebly.com Content Human Alimentary Canal Chemical Digestion Absorption and Assimilation Learning Outcomes: Candidates should be able to: (a) describe the functions of main regions of the alimentary canal and the associated organs: mouth, salivary glands, oesophagus, stomach, duodenum, pancreas, gall bladder, liver, ileum, colon, rectum, anus, in relation to ingestion, digestion, absorption, assimilation and egestion of food, as appropriate # Region Function Description of function 1 Mouth Ingestion Has teeth which chews to break down large pieces of food into smaller pieces to increase surface area to volume ratio of food lumps 2 Salivary gland Ingestion Digestion Secretes saliva containing mucin which softens the food so that swallowing the food lumps is easier Secretes saliva containing salivary amylase is secreted by salivary glands through salivary ducts into the mouth, which digests some starch into maltose 3 Oesophagus Digestion Induces peristalsis (along with other parts of the alimentary canal) that allows food to be mixed with digestive juices easily and broken down further through churning, increasing rate of collision of enzymes and substrates and rate of digestion 4 Stomach Digestion [Initial process] Secretes gastric juice to convert pepsinogen to pepsin, and prorennin to rennin [Eventual process] Secretes gastric juice containing hydrochloric acid which provides a suitable ph for pepsin to digest proteins to polypeptides, and rennin to turn soluble milk proteins insoluble so that it can be fully digested before moving to small intestine [Combination of the above processes] Digestion in the stomach turns the partly digested food into liquified chyme, enabling food to pass into the duodenum in small amounts instead of altogether increasing surface area to volume ratio and giving small intestine more time to digest 5 Duodenum Digestion Secretes intestinal juice 1. Carbohydrases: Maltase converts maltose to glucose 2. Proteases: Erepsin digests polypeptides to amino acids 6 Pancreas Digestion Secretes pancreatic juice 1. Amylase: Pancreatic amylase digests starch to maltose 2. Lipase: Pancreatic lipase digests fats to fatty acids and glycerol 3. Proteases: Trypsin converts remaining protein to polypeptides Assimilation Secretes the hormone glucagon to stimulate the liver to convert glycogen into glucose when blood glucose concentration is low, and transported to the cells and oxidised to produce more energy 24 Consylladated by Lim Ting Jie

25 # Region Function Description of function syllacon.weebly.com 7 Gall bladder Digestion Storage and release area of bile from the liver, assisting emulsification 8 Liver Digestion Secretes bile released from gall bladder to emulsify fats 1. Lower surface tension of fats 2. Smaller fat droplets 3. Lipase digests fats faster Assimilation Egestion Carries out deamination of excess amino acids by converting part of it to glucose that can be used to provide more energy Carries out deamination of excess amino acids by converting part of it to urea Breaks down haemoglobin from red blood cells to be converted into bile 9 Ileum Absorption Blood capillaries transport sugars and amino acids to the hepatic portal vein Lacteals transport minute fat globules of glycerol and fatty acids to lympatic vessels Hepatic portal vein Lymphatic vessels Absorption Absorption Transports sugars and amino acids to the liver to convert excess of them into glycogen and urea, then distributing remaining to the body parts Transports small fat globules to the bloodstream to be distributed to the rest of the body 10 Colon Absorption Water and mineral salts absorbed Egestion Controls emptying of the rectum 11 Rectum Egestion Intestinal wall secretes mucus that lubricates undigested contents, which stays for 36 hours 12 Anus Egestion Stores undigested food as faeces temporarily # Process Ingestion Digestion Absorption Assimilation Egestion 1 Mouth 2 Salivary gland 3 Oesophagus 4 Stomach 5 Duodenum 6 Pancreas 7 Gall bladder 8 Liver 9 Ileum 10 Colon 11 Rectum 12 Anus 25 Consylladated by Lim Ting Jie

26 Diagram 26 Consylladated by Lim Ting Jie

27 (b) describe peristalsis in terms of rhythmic wave-like contractions of the muscles to mix and propel the contents of the alimentary canal Term Peristalsis Definition Rhythmic wave-like contractions of muscles of the gut Peristalsic action Mixes food well with digestive juices easily Function Increases rate of collision of enzymes and substrates and rate of digestion Propel food down the gut Pushing of food from behind down the gut Providing space for food in front to move down the gut By contracting of internal circular muscles and relaxing external longitudinal muscles, which constricts the lumen By relaxing of internal circular muscles and contracting external longitudinal muscles in front of the food provides space for food to move forward easily Churning to create chyme Enables food to pass into the duodenum in small amounts instead of altogether, giving small intestine more time for digestion Diagram (c) describe digestion in the alimentary canal, the functions of a typical amylase, protease and lipase, listing the substrate and end-products Large molecule Enzyme Substrate End-products Carbohydrates Amylase Starch Maltose Proteins Proteases Pepsin Polypeptides Proteins Erepsin Amino acids Polypeptides Fats Lipase Glycerol + Fatty acids Fat + Water 27 Consylladated by Lim Ting Jie

28 (d) describe the structure of a villus and its role, including the role of capillaries and lacteals in absorption Region in small intestine Villus Blood capillaries Lacteals Role Highly folded with microvilli (in-foldings) to increase surface area to volume ratio for faster rates of absorption Transports sugars and amino acids to the hepatic portal vein Transports minute fat globules of glycerol and fatty acids to lympatic vessels Adaptation of small intestine Highly folded with villi and microvilli of finger-like structures Epithelial wall is one cell thin Long and making up 60% of the small intestine Many capillaries in intestinal wall and villi transports food molecules away from intestine Significance Increases surface area to volume ratio for faster rates of absorption Decreases time needed for food molecules to travel through the wall, increasing rate of absorption Ensures sufficient time for complete absorption Maintains concentration gradient of digested food substances through epithelial wall (e) state the function of the hepatic portal vein as the route taken by most of the food absorbed from the small intestine Region Hepatic portal vein Function Route taken by most of the food absorbed from the small intestine to be distributed to other body parts Route of food taken from small intestine to other body parts 28 Consylladated by Lim Ting Jie

29 (f) state the role of the liver in: carbohydrate metabolism fat metabolism breakdown of red blood cells metabolism of amino acids and the formation of urea breakdown of alcohol # Roles of liver Description of roles of liver 1 Carbohydrate metabolism Insulin produced by the islets of Langerhans of the pancreas stimulates the liver to convert glycogen to glucose and converts glucose back to glycogen by glucagon and adrenalin if the concentration ratio of glucose is high to regulate blood glucose concentration 2 Fat metabolism Secretes bile containing bile salts and bile pigments that emulsify fats, enabling it to turn into more, smaller droplets with high surface area to volume ratio and lower surface tension, increasing the digestion rate between fats and water into fatty acids and glycerol by lipase 3 Breakdown of red blood cells 4 Amino acid metabolism 5 Breakdown of alcohol Haemoglobin in red blood cells is broken down into iron and bile salts to be excreted out of the body through faeces Deanimates amino acids and converts part of them into glycogen, to be stored in liver and muscles that can convert it to glucose of blood glucose level is low The other part will be converted to urea, to be excreted through urine Alcohol dehydrogenase from liver breaks down alcohol into acateldahyde compounds that can be broken down during respiration to release energy However, if alcohol used excessively, acids are secreted in the stomach that might cause gastric ulcers In worser cases, cirrhosis will destroy liver cells, diminishing its function (g) describe the effects of excessive consumption of alcohol: reduced self-control, depressant, effect on reaction times, damage to liver and social implications # Effects Description of effects of excessive alcohol consumption 1 Depressant Alcohol inhibits the function of the central nervous system by disrupting the brain s communication pathways 2 Reduced self-control 3 Effect on reaction times 4 Damage to liver 5 Social implications As a result, it is more difficult for the person to think clearly and move with coordination It also takes a longer time for the person to process information For example, the slower rate of reaction to sudden changes in traffic to makes it easier for drivers to cause an accident Liver inflammations may occur For example, cirrhosis will destroy liver cells, diminishing its function Furthermore, excessive alcohol use can effect all areas of a person's life, including family, work and personal relationships 1. Family problems: Arguments over someone's drinking can cause family and relationship problems that may lead to break up 2. Work problems: Drinking alcohol at work and hangovers can lead to poor performance and accidents at work, while illness can result in absenteeism 3. Legal problems: Drink-driving may lead to fines, loss of license and even imprisonment Source: Use the knowledge gained in this section in new situations or to solve related problems. 29 Consylladated by Lim Ting Jie

30 5. Nutrition in Plants syllacon.weebly.com Content Leaf Structure Photosynthesis Learning Outcomes: Candidates should be able to: (a) identify and label the cellular and tissue structure of a dicotyledonous leaf, as seen in transverse section under the microscope and describe the significance of these features in terms of their functions, such as the: distribution of chloroplasts in photosynthesis stomata and mesophyll cells in gaseous exchange vascular bundles in transport Features Aspects Significance Distribution of chloroplasts in photosynthesis Stomata and mesophyll cells in gaseous exchange Vascular bundles in transport Epidermal layer Palisade mesophyll cells Spongy mesophyll cells Increase stomatal receival of carbon dioxide Decrease stomatal loss of water vapour All mesophyll cells (carbon dioxide and oxygen) Spongy mesophyll cells Xylem (top) for loss of water vapour Phloem (bottom) for transport of sugars Cuticle of the upper and lower epidermis Contains numerous chloroplasts, located right below the upper epidermis and closely packed together to absorb maximum sunlight for photosynthesis Contains chloroplasts to maximise photosynthesis of plant In sunlight, photosynthesis occurs Energy is used to pump potassium ions into the guard cells, increasing K + concentration and decreasing water potential of guard cells, causing water to enter these guard cells by osmosis This turns them turgid and pulls stomata open, resulting in more carbon dioxide received to facilitate higher photosynthesis rates under sunlight At night, K + ions accumulated in the day diffuse out of the guard cells, increasing water potential and causing water to leave the guard cells through osmosis As the cells are more flaccid, the stomatal pore closes Under high temperature, excess evaporation (transpiration) of water causes the guard cells to be more flaccid, closing the stomatal pore. Covered with a thin film of water for gases to dissolve in to allow rapid diffusion of carbon dioxide and oxygen in and out of the mesophyll cells Irregular with large intercellular air spaces among them to allow rapid diffusion of gases from stomata to the vascular bundles through the leaf Transports water and dissolved mineral salts from the roots to the leaf so that once out of the xylem, the water and mineral salts move from cell to cell right through the mesophyll of the leaf by osmosis When the mesophyll cells receive water from xylem and carbon dioxide from the air through the stomata, they can manufacture food under light by photosynthesis, in which the phloem will transport sugars to other plant parts Closely packed with waxy cuticle that prevents excessive evaporation (transpiration) of water Transparent to allow sunlight to penetrate the leaf easily 30 Consylladated by Lim Ting Jie

31 Diagram (b) state the equation, in words and symbols, for photosynthesis Equation for photosynthesis In words Carbon dioxide + Water Glucose + Oxygen In symbols 6 CO H 2 O C 6 H 12 O O 2 (c) describe the intake of carbon dioxide and water by plants Processes Photosynthesis Water potential Turgidity of guard cells Description of processes Photosynthesis occurs whenever there is sunlight Energy is used to pump potassium ions into the guard cells, increasing K + concentration and decreasing water potential of guard cells, causing water to enter these guard cells by osmosis This turns them turgid and pulls stomata open, resulting in more carbon dioxide (and water vapour) received to facilitate higher photosynthesis rates under sunlight 31 Consylladated by Lim Ting Jie

32 (d) state that chlorophyll traps light energy and converts it into chemical energy for the formation of carbohydrates and their subsequent storage Substance Chlorophyll Function Traps light energy and converts it into chemical energy for the formation of carbohydrates via photosynthesis and their subsequent storage as starch Components of photosynthesis Significance Reactants (raw materials) Activation energy Endproducts Carbon dioxide Water Chlorophyll traps light and converts it to chemical energy Glucose Sucrose Starch Oxygen Produced by all living organisms during respiration are removed in photosynthesis for plants to produce food Required to produce glucose as it contains the hydrogen element Chemical energy would be used to start the photochemical reaction to convert carbon dioxide and water to glucose and oxygen Transported through the phloem to various parts of the plant by translocation Used as a reactant of respiration to release energy for cellular activities in the plant Excess glucose produced in the leaf is converted to sucrose and transported to storage organs (e.g. seeds) Excess glucose produced in the leaf is converted to starch to be stored temporarily, converted back mostly at night when photosynthesis stops Oxygen is produced and used by all organisms in respiration, allowing them to release energy 32 Consylladated by Lim Ting Jie

33 (e) investigate and discuss the effects of varying light intensity, carbon dioxide concentration and temperature on the rate of photosynthesis (e.g. in submerged aquatic plant) # Factors Effects 1 Light intensity When light intensity increases, the rate of photosynthesis generally increases When light intensity is at light compensation point When light intensity is at light saturation point Rate of photosynthesis is equal rate of respiration (i.e. rate of carbon dioxide intake is equal to that of oxygen) Any rise in light intensity after this point will cause rate of photosynthesis to be greater than rate of respiration Rate of photosynthesis is maximum Any rise in light intensity after this point will not affect rate of photosynthesis (i.e. rate of photosynthesis remains constant) 2 Carbon dioxide concentration When carbon dioxide concentration increases, the rate of photosynthesis generally increases This is because carbon dioxide is a key reactant in photosynthesis Rate of photosynthesis remains constant eventually as carbon dioxide concentration rises further 3 Temperature When temperature increases up to 40 o C, the rate of photosynthesis increases This is because enzymes involved in photosynthesis are more active When temperature is increases beyond 40 C, the rate of photosynthesis drops This is because enzymes involved in photosynthesis are denatured 33 Consylladated by Lim Ting Jie

34 (f) discuss light intensity, carbon dioxide concentration and temperature as limiting factors on the rate of photosynthesis Term Definition Clarification Limiting factor The factor that directly increases the rate of a process if its quantity is increases and is the lowest in concentration among all other factors While a process can be affected by many factors, only one of the factors can be the limiting factor at any given time (i.e. the one that is lowest in concentration) # Factors When the factor is limiting Graph 1 Light intensity When light intensity increases, the rate of photosynthesis generally increases In this case, light intensity is the limiting factor At light saturation point, rate of photosynthesis is maximum and cannot increase further In this case, either carbon dioxide or temperature replaces light intensity as the limiting factor 2 Carbon dioxide concentration Carbon dioxide is an important limiting factor as it makes up only 0.03% of air It ceases to be the limiting factor when rate of photosynthesis is maximum 3 Temperature When light intensity is low, temperature cannot be a limiting factor When light intensity is high, temperature is a likely limiting factor Temperature ceases to be the limiting factor when rate of photosynthesis starts to fall Relationship between the above-mentioned factors Use the knowledge gained in this section in new situations or to solve related problems 34 Consylladated by Lim Ting Jie

35 6. Transport in Flowering Plants syllacon.weebly.com Content Water and Ion Uptake Transpiration and Translocation Learning Outcomes: Candidates should be able to: (a) identify the positions and explain the functions of xylem vessels, phloem (sieve tube elements and companion cells) in sections of a herbaceous dicotyledonous leaf and stem, under the light microscope Xylem Phloem Plant parts Sieve tube elements Companion cells Functions Transport mineral salts and water through lignified walls, which provide mechanical strength to the plants Allows water to move efficiently by not having cross walls, which maintains a continuous lumen Protoplasm of the sieve tube is disintegrated and the sieve plate walls contain holes, allowing rapid movement of food from the leaves due to less obstructions Contain mitochondria to release energy needed for active transport of food from the leaves to other parts of the plant Diagrams Xylem and phloem in leaf Xylem and phloem in stem Note: Xylem is shaded in the diagrams while phloem is not (b) relate the structure and functions of root hairs to their surface area, and to water and ion uptake Structure Long and narrow (surface area) Contains cell sap (water uptake) Mitochondria present (ion uptake) Function Increases surface area to volume ratio to allow rate of absorption of mineral salts and water to be increased Cell sap has less water potential than soil to allow water to diffuse into the cell down a concentration gradient Releases energy during respiration for the cell to allow active transport to occur if the cell has a higher concentration of ions and mineral salts 35 Consylladated by Lim Ting Jie

36 (c) explain the movement of water between plant cells, and between them and the environment in terms of water potential (Calculations on water potential are not required). Direction Movement Explanation From soil to root hair cell From root hair cell to cortex cell beside From the series of cortex to xylem vessel Xylem vessel of leaves to the spongy mesophyll cell Spongy mesophyll cell to atmosphere Either: Water molecules move from the soil water across the partially permeable cell membrane into the root hair cell by osmosis Or: Root hair cell absorbs water molecules from the soil water across the partially permeable cell membrane by active transport Water molecules move from the root hair cell into the cortex cell by osmosis The above movement of water continues from cell to cell through the series of neighbouring cortex cells until the water molecules reach the xylem tissue in the root Water molecules move from the xylem tissue to the mesophyll cells by osmosis Water evaporates from the mesophyll cells Water moves from the thin film of moisture into the intercellular air spaces, accumulating in the air spaces that are near the stomata This occurs if there is a higher water potential in soil water than the root hair cell This occurs if there is a lower water potential in soil water than the root hair cell (energy from cell respiration is used for active transport) The root hair cell has higher water potential than the cortex cell beside it Water molecules travel up the xylem through transpiration pull to the leaves There is a higher water potential in xylem tissue in the leaf than the mesophyll cells Water forms a thin film of moisture over the mesophyll surfaces and turns into water vapour Water vapour diffuses through the stomata to the drier air outside the leaf through transpiration 36 Consylladated by Lim Ting Jie

37 (d) outline the pathway by which water is transported from the roots to the leaves through the xylem vessels Outline Diagram 37 Consylladated by Lim Ting Jie

38 (e) define the term transpiration and explain that transpiration is a consequence of gaseous exchange in plants Term Definition Explanation Transpiration The loss of water vapour from the aerial parts of a plant, especially through the stomata of the leaves As water vapour evaporates from the film of water on the spongy mesophyll cells, the water potential of the cell sap decreases The mesophyll cells then absorb water by osmosis from the xylem vessels deep inside the leaf, removing water from the xylem vessels A suction force results, pulling the whole column of water up the xylem vessels Thus transpiration is a consequence of gaseous exchange (f) describe and explain: the effects of variation of air movement, temperature, humidity and light intensity on transpiration rate how wilting occurs # Factor Effect Explanation 1 Air movement As increase in air movement increases transpiration rate Wind blows away water vapour that accumulates outside the stomata, increasing water vapour concentration gradient 2 Temperature of air An increase in temperature increases transpiration rate Rate of evaporation increases as temperature increases 3 Humidity of air An increase in humidity decreases transpiration rate 4 Light intensity An increase in light intensity increases transpiration rate Intercellular air spaces are normally saturated with water vapour Increase in humidity (water vapour in the air) decreases the water vapour concentration gradient As light increases, the size of the stomata on the leaf increases and widens Term Description Explanation Advantage Disadvantage Wilting Loss of rigidity of non-woody parts of plants due to loss of turgor Any of above factors can cause rate of transpiration to be more than that of absorption Cells lose turgor due to loss of water and therefore wilts Reduces transpiration Leaf folds up, reducing surface area exposed to light Guard cells become flaccid and stomata close Reduces rate of photosynthesis When stomata close, amount of carbon dioxide entering plant is reduced, which becomes the limiting factor When folded, surface area is reduced, causing light received to be limited (g) define the term translocation as the transport of food in the phloem tissue and illustrate the process through translocation studies Term Definition Illustration Translocation Transport of manufactured food substances such as sugars and amino acids in phloem tissues When the mouthpart of an aphid penetrates a leaf or stem, anaesthetise it with carbon dioxide while it is feeding Cut off body of aphid and analyse liquid from the cut end of mouth Use the knowledge gained in this section in new situations or to solve related problems. 38 Consylladated by Lim Ting Jie

39 7. Transport in Humans syllacon.weebly.com Content Circulatory System Learning Outcomes: Candidates should be able to: (a) identify the main blood vessels to and from the heart, lungs, liver and kidney Circulatory system Diagram 39 Consylladated by Lim Ting Jie

40 (b) state the role of blood in transport and defence red blood cells haemoglobin and oxygen transport plasma transport of blood cells, ions, soluble food substances, hormones, carbon dioxide, urea, vitamins, plasma proteins white blood cells phagocytosis, antibody formation and tissue rejection platelets fibrinogen to fibrin, causing clotting # Components of blood Features Functions 1 Red blood cells Haemoglobin Oxygen is being transported by haemoglobin in red blood cells Absence of nucleus allows space for haemoglobin which combines reversibly with oxygen, binding easily with oxygen to carry it in blood and unbinding to release oxygen to requiring parts Oxygen transport Elasticity 2 Plasma Transport of substances within body Circular and biconcave shape increases surface area to volume ratio and thus rate of absorption and release of oxygen Able to turn into a bell shape, allowing it to squeeze through blood vessels of diameter smaller than itself, easing movement through lumen and increasing surface area to volume ratio to speed up oxygen exchange Transports substances like blood cells, soluble food substances, plasma proteins, water, ions, carbon dioxide, vitamins, hormones and urea around the body 3 White blood cells Phagocytosis Phagocytes engulf and ingest pathogens and harmful foreign bacteria Antibody formation Tissue rejection 4 Platelets Blood clotting Lymphocytes produce antibodies that clump foreign bacteria together, protecting the body against fatal bacteria and viruses Lymphocytes produce antibodies to destroy foreign organs, as organs from another person are usually treated as a foreign body by his immune system When tissues are damaged, enzymes released from platelets convert prothrombin to thrombin so that fibrinogen can be converted to insoluble fibrin, meshing up to trap blood cells, preventing them from flowing out (c) list the different ABO blood groups and all possible combinations for the donor and recipient in blood transfusions Blood group Components Combinations for donor and recipient Antigens Antibodies Give blood to Receive blood from Importance AB A A, B A - B AB A, AB A, B AB, O A, O Failure to abide by the guidelines of giving and B B A B, AB B, O receiving blood will result in O - A, B A, B, AB, O O agglutination 40 Consylladated by Lim Ting Jie

41 (d) relate the structure of arteries, veins and capillaries to their functions syllacon.weebly.com Vessels Structure Features Functions Arteries Small lumen size At higher pressure this allows fast rate of flow of blood to body parts Veins Elastic Muscular Semi lunar valves present Parts of vein are found alongside skeletal muscles To withstand high pressure from the small lumen size and recoil for blood to travel in spurts under the high pressure Enables artery to dilate and constrict by the relaxation and contraction of muscles of arterial wall To prevent the backflow of blood Contracting of skeletal muscles during exercise compresses the vein, exerting more pressure and pushing blood flow forward at a faster rate Capillaries Small lumen of arteries and large lumen of veins Endothelium partially permeable Capillaries branch repeatedly Higher pressure of the arteries and lower pressure of the veins allow constant flow of blood through the capillaries Enables certain substances to diffuse quickly through the capillary walls Increases cross sectional area, lowers blood pressure, slows flow of blood, increases time for exchange of substances (e) describe the transfer of materials between capillaries and tissue fluid Key question How is tissue fluid is formed? Which substances are transported from the capillaries? Which substances are transported into the capillaries? Exam response High pressure at the arterial end of capillaries force out diluted blood plasma and white blood cells, giving rise to tissue fluid Dissolved food substances and oxygen are transported from the blood in blood capillaries, into the tissue fluid, then to the tissue cells Excretory waste products diffuse from the tissue cells into the tissue fluid, then to the blood, to be transported to excretory waste organs Diagram 41 Consylladated by Lim Ting Jie

42 (f) describe the structure and function of the heart in terms of muscular contraction and the working of valves Structure Median septum Chamber valves Chordae tendineae Ventricles thicker muscular walls than atria Left ventricle thicker muscular walls than right ventricle Function Divides the heart to the left side and the right side, separating both sides so that blood flows in only one direction as oxygenated and deoxygenated blood do not mix together Tricuspid, bicuspid and semi lunar valves prevent the blood from flowing backwards, ensuring that blood flows in only one direction Attached to the wall of ventricles to prevent the flaps of the valves from inverting during ventricular contraction Ventricles would be able to pump blood a longer distance to ease the pumping of blood out of the heart (since blood leaves the heart via the ventricles) Right ventricle able to pump blood at a lower pressure along a small distance, ensuring that the slow rate of blood flow allows sufficient time for gaseous exchange at the lungs (unlike left ventricle that pumps blood around the body) Diagram 42 Consylladated by Lim Ting Jie

43 (g) outline the cardiac cycle in terms of what happens during systole and diastole. (Histology of the heart muscle, names of nerves and transmitter substances are not required) Happenings Atrial Systole Ventricular Systole Ventricular Diastole Atria Contract [1] Relax Relax Ventricles Relax Contract Relax [3] Blood Flow From atria to ventricles From ventricles to aorta and pulmonary artery From vena cava and pulmonary veins to atria Pressure Ventricular pressure increases Pressure in ventricle higher than aorta Ventricular pressure decreases Tricuspids and Bicuspids Open Close ( lub produced) Open [4] Semi-Lunar Valves Closed Forced open [2] Close ( dub produced) Diagram 43 Consylladated by Lim Ting Jie

44 (h) describe coronary heart disease in terms of the occlusion of coronary arteries and list the possible causes, such as diet, stress and smoking, stating the possible preventative measures Coronary arteries Coronary heart disease (CHD) Function Significance Explanation Coronary arteries lie on the outside of the heart and carry blood to muscles in the walls of the heart Heart muscles must be supplied with oxygen and nutrients via blood in order to pump blood around the body Blocked or narrowed coronary arteries reduces blood supply to the walls of the heart greatly This causes the supply of oxygen and nutrients to the muscles in the walls of the heart to be insufficient Heart will not be able to pump blood around the body Causes of CHD Description of causes of CHD Cholesterol metabolism Size of lumen Blood clots Insufficient supply of oxygen A diet rich in cholesterol and saturated animal fats causes fatty substances like cholesterol to be deposited on the inner surface of coronary arteries Narrowed lumen increases blood pressure from rough inner artery surfaces Risk of blood clots being trapped in the coronary arteries via thrombosis Supply of blood and oxygen may be insufficient, resulting in insufficient energy released to heart muscles Emotional stress and smoking increases the risk of atherosclerosis Measures Proper diet Proper stress management Decrease or stop smoking Regular physical exercise Description of measures to prevent CHD Use of polyunsaturated plant fats and dietary fibres will lower cholesterol level in blood Reduces risk of a heart attack as people with high stress levels tend to require more oxygen levels Nicotine increases blood pressure and risk of blood clotting Carbon monoxide increases risk of fatty deposits Strengthens the heart and maintains elasticity of arteriole walls, reducing high blood pressure Use the knowledge gained in this section in new situations or to solve related problems 44 Consylladated by Lim Ting Jie

45 8. Respiration in Humans syllacon.weebly.com Content Human Gas Exchange Aerobic Respiration Anaerobic Respiration Learning Outcomes: Candidates should be able to: (a) identify on diagrams and name the larynx, trachea, bronchi, bronchioles, alveoli and associated capillaries Diagrams Larynx Bronchiole Alveoli Trachea Bronchus Capillaries Bronchioles 45 Consylladated by Lim Ting Jie

46 (b) state the characteristics of, and describe the role of, the exchange surface of the alveoli in gaseous exchange Characteristics Adaptation Relation to role Rich supply of blood capillaries Thin film of moisture on internal surface of alveoli Large surface area of alveoli One cell thick wall of alveoli Ensures a constant concentration gradient of gas molecules Allows oxygen to dissolve and diffuse into the alveoli easily Faster rate of diffusion of gases with high surface area to volume ratio Shorter distance for gas molecules to diffuse across it increases rate of diffusion and efficiency Helps the lungs ensure continuous uptake of oxygen for respiration in order to release energy by being specially adapted for rapid transfer of gases between the lungs and the blood capillaries Diagrams 46 Consylladated by Lim Ting Jie

47 (c) describe the removal of carbon dioxide from the lungs, including the role of the carbonic anhydrase enzyme Relation Processes Description Formation of carbon dioxide Inspiration Oxygen leaves alveoli Respiration Oxygen is taken in through the nose and diffuses from the alveoli in lungs to blood capillaries heading to the heart After leaving the lungs and the heart, oxygen is distributed to tissue cells for respiration Glucose reacts with oxygen to produce carbon dioxide and water Removal of carbon dioxide Carbon dioxide leaves the capillaries of tissue cells Acidification in red blood cell Deassociation, entry to plasma Water and carbon dioxide react to form carbonic acid with the help of the enzyme carbonic anhydrase Carbonic acid is converted to hydrogen and carbonate ions (hydrogencarbonate ions) and leaves the red blood cell and enters blood plasma to be transported Carbon dioxide enters alveoli Expiration Hydrogencarbonate ions are converted back to carbonic acid then to water and carbon dioxide in red blood cells by carbonic anhydrase, thereafter diffusing out to plasma, then to alveoli Carbon dioxide is expelled when expiration occurs (d) describe the role of cilia, diaphragm, ribs and intercostal muscles in breathing Part of lungs Inspiration Expiration Diaphragm Contracts and flattens Relaxes and arches upwards Intercostal muscles Relax internal, contract external (RICE) External relaxes, internal contracts (ERIC) Ribs Upwards and outwards Downwards and inwards Sternum Up and forward Moves down back to original position Air pressure to force air in or out Decreases in lungs, atmospheric pressure is higher Increases in lungs, atmospheric pressure is lower 47 Consylladated by Lim Ting Jie

48 (e) describe the effect of tobacco smoke and its major toxic components nicotine, tar and carbon monoxide, on health Components of tobacco smoke Characteristics Effects on health Nicotine Blood clots more easily Increases risk of blood clots in blood vessels that might potentially obstruct flow of blood through them Tar Carbon monoxide May induce cancer in the epithelium that paralyses cillia lining air passages Damages lining of blood vessels Increases rate of fat deposition on inner arterial wall Combines more readily than oxygen to form carboxyhaemoglobin Air sacs are blocked, reducing efficiency of gas exchange Dust particles trapped in mucus lining the airways cannot be removed Increases risk of blood clots in blood vessels that might potentially obstruct flow of blood through them Obstructions slow down blood flow, decreasing efficiency of rate of oxygen distribution and carbon dioxide removal, slowing glucose production Reduces oxygen transport efficiency of red blood cells as oxygen has to compete with carbon monoxide to bind with haemoglobin Effects of tobacco smoke on health Chronic Bronchitis due to excessive irritant particles within smoke Emphysema due to persistent violent coughing of chronic brochitis Explanation Epithelium lining the airways is inflamed Excessive mucus secreted by the epithelium Mucus lining airways cannot be removed Persistent coughing needed to clear airways and breathe, increasing the risk of lung infections and emphysema Severe breathlessness as airways become blocked Severe breathlessness as airways become blocked Lungs are inflated with air Lungs lose elasticity Partition walls between air sacs break in violent coughing Surface area for gaseous exchange decreases More severe breathlessness (f) define and state the equation, in words and symbols, for aerobic respiration in humans Equation for aerobic respiration Oxidation of food substances to release a large amount of energy (CO 2 + H 2 O as waste) Glucose Oxygen Carbon dioxide Water Energy is released C 6 H 12 O 6 6 O 2 6 CO 2 6 H 2 O Large amount of energy (g) define and state the equation, in words only, for anaerobic respiration in humans Equation for anaerobic respiration Breakdown of food substances in the absence of oxygen Less energy released than aerobic Glucose With the absence of oxygen Lactic acid Little energy 48 Consylladated by Lim Ting Jie

49 (h) describe the effect of lactic acid in muscles during exercise Anaerobic respiration During exercise Effect of lactic acid Right after exercise When the intensity of exercise is raised, muscular contractions become more vigorous Aerobic respiration is unable to meet the higher energy demand, so anaerobic respiration also occurs This causes lactic acid to build up slowly in muscles Glucose Lactic acid + Small amount of energy When lactic acid concentrations become high enough, the high acidity causes muscular pains and fatigue, increasing the need for the body to rest and recover through deep breathing Oxygen debt is paid off through deep breathing Lactic acid is quickly oxidised to form carbon dioxide and water Lactic acid + Oxygen Carbon dioxide + Water The oxidation of some of the lactic acid provides energy for the conversion of the remaining lactic acid to glucose Use the knowledge gained in this section in new situations or to solve related problems 49 Consylladated by Lim Ting Jie

50 9. Excretion in Humans syllacon.weebly.com Content Structure and Function of Kidneys Kidney Dialysis Learning Outcomes: Candidates should be able to: (a) define excretion and explain the importance of removing nitrogenous and other compounds from the body Term Definition Importance Excretion Process by which metabolic waste products and toxic materials are removed from the body of an organism Metabolic waste products and toxic materials can be poisonous and harmful if they accumulate in the body If they cannot be converted to harmless substances, excretion is the only way to remove them 50 Consylladated by Lim Ting Jie

51 (b) outline the function of kidney tubules with reference to ultra-filtration and selective reabsorption in the production of urine Processes Kidney portions Functions Ultrafiltration Renal capsule leading to each tubule Glucose, mineral salts, amino acids, water and nitrogenous waste products is ultrafiltrated from the glomerulous to the renal capsule Afferent arteriole is wider than efferent arteriole Creates a high hydrostatic blood pressure Basement membrane covering the capillaries has small pores Allows only some substances to pass through by being partially permeable Selective reabsorption Urine collection Proximal convoluted tubule Loop of Henle Distal convoluted tubule Collecting tubule Renal pelvis, ureter, urinary bladder, urethra Some mineral salts, all glucose and all amino acids are reabsorbed into blood capillaries Some water reabsorbed into blood capillaries Some water and some salts reabsorbed into blood capillaries Some water reabsorbed into blood capillaries The remaining solution of excess water, excess salt and nitrogenous waste products (e.g. urea, uric acid and creatinine) form urine and is stored in urinary bladder Diagram (c) outline the role of anti-diuretic hormone (ADH) in the regulation of osmotic concentration Stimulus Receptor Effectors Corrective mechanism Water potential in blood plasma rises Hypothalamus in the brain monitors and senses a rise in water potential Pituitary gland Less anti-diuretic hormone (ADH) released from the pituitary gland into the bloodstream Kidney tubules reabsorb less water into blood capillaries Urine turns more dilute and increases in volume Water potential in blood plasma falls Hypothalamus in the brain monitors and senses a fall in water potential Pituitary gland More anti-diuretic hormone (ADH) released from pituitary gland into bloodstream Kidney tubules reabsorb more water into blood capillaries Urine turns more concentrated and decreases in volume 51 Consylladated by Lim Ting Jie

52 (d) outline the mechanism of dialysis in the case of kidney failure Mechanism Blood is drawn from the artery in patient s arm It is then pumped into a tubing with partially permeable walls bathed in a specially controlled dialysis machine Small molecules like urea and other metabolic waste products diffuse in the fluid Blood cells, platelets and big molecules remain in the tubing The filtered blood is then returned to a vein in the patient s arm Outline Ensures that excretion is performed without much disturbance on the body s homeostatic system Takes the place of the failed kidney to enable excretion to continue taking place Ensures that there is no change in rate of flow of blood between the artery and vein Diagrams Adaptations Same concentration of essential substances like mineral salts Long, narrow and coiled Does not contain any metabolic waste products, excess water and mineral salts Direction of flow of dialysis fluid is opposite that of blood flow Functions Ensures that they do not diffuse out of the bloodstream, or that minerals can diffuse into the bloodsteam if it lacks minerals Increases surface area to volume ratio to speed up exchange Concentration gradient allows these products to diffuse out of the tubing, and water potential of blood to be maintained Maintains concentration gradient to remove waste products Use the knowledge gained in this section in new situations or to solve related problems 52 Consylladated by Lim Ting Jie

53 10. Homeostasis syllacon.weebly.com Content Principles of Homeostasis Skin Learning Outcomes: Candidates should be able to: (a) define homeostasis as the maintenance of a constant internal environment Term Definition Full definition Homeostasis The maintanence of a constant internal environment The maintanence of a constant internal environment that occurs whenever a receptor detects a change in condition of the internal environment, stimulates a self-regulatory corrective mechanism to bring about the reverse effect of the stimulus, and receives a negative feedback when the condition is restored (b) explain the basic principles of homeostasis in terms of stimulus resulting from a change in the internal environment, a corrective mechanism and a negative feedback Principles Stimulus Receptor Corrective mechanism Negative feedback Explanation A change in the internal environment that is from the normal condition requires homeostasis to maintain it and bring the condition back to normal Organs or structures that can detect the stimulus to stimulate the effector Mechanism is stimulated to bring about the reverse effect of the stimulus, usually through regulatory fluids, to correct the condition until it is normal again After a system has brought about an opposite effect to changes in the system, negative feedback is the process of restoring the system to its original state, undisturbed, through nerve impulses to the receptor (c) identify on a diagram of the skin: hairs, sweat glands, temperature receptors, blood vessels and fatty tissue Diagram of the skin temperature receptor 53 Consylladated by Lim Ting Jie

54 (d) describe the maintenance of a constant body temperature in humans in terms of insulation and the role of: temperature receptors in the skin, sweating, shivering, blood vessels near the skin surface and the co-ordinating role of the hypothalamus Maintanence Parts Final effect Mechanism Insulation Fatty adipose tissue Slows down heat production Found beneath the dermis to store fat Slows the loss of heat through insulation Temperature sensing Temperature receptors and hypothalamus of the brain Via receptors and effectors of homeostasis Senses temperature changes from surroundings Sends nerve impulses to hypothalamus of the brain, which receives information to be activated Sends nerve impulses to target organs Ventilation Lungs Speeds up heat loss More carbon dioxide and water vapour is exhaled, causing heat to be lost through these gases Metabolic rate Cells in general Speeds up heat production Increase in metabolic rate Slows down heat production Decrease in metabolic rate Sweating Sweat glands, duct and pores Speeds up heat loss Sweat containing latent heat of vapourisation is produced by the sweat duct and released from the sweat pores will evaporate, thus removing heat Shivering Skeletal muscles Speeds up heat production Contracts spasmodically in a reflex action known as shivering to increase heat production Blood vessels near the skin surface Arterioles, capillaries and venules Speeds up heat loss Arterioles vasodilate to allow more blood flow to capillaries, transferring more heat by conduction and radiation to the skin surface then atmosphere, bringing less heat back through the venules Shunt vessels Speeds up heat loss Shunt vessels constrict to allow less blood to be brought back to body parts through the venules and more blood to flow to capillaries, thus less heat is brought back to the body parts Slows down heat loss Shunt vessels dilate to allow more blood to be brought back to body parts through the venules and less blood to flow to capillaries, thus more heat is brought back to the body parts Use the knowledge gained in this section in new situations or to solve related problems 54 Consylladated by Lim Ting Jie

55 11. Co-ordination and Response syllacon.weebly.com Content Receptors Eye Nervous System Neurones (Reflex Action) Effectors Endocrine Glands Learning Outcomes: Candidates should be able to: (a) state the relationship between receptors, the central nervous system and the effectors Part Receptors Central nervous system Effectors Relationship in response Gathers information and converts it into electrical signals known as nerve impulses Nerve impulses are transmitted through nerves in the peripheral nervous system to the central nervous system of the brain and spinal cord to interpret the nerve impulses and is stimulated to take action Impulses are transmitted by nerve impulses to effectors to carry out intended actions (b) describe the gross structure of the eye as seen in front view and in horizontal section Diagram cornea choroid pupil iris lens suspensory ligaments ciliary body fovea retina optic nerve to brain sclera 55 Consylladated by Lim Ting Jie

56 (c) state the principal functions of component parts of the eye in producing a focused image of near and distant objects on the retina # Eye part for imagery Function 1 Retina Light sensitive area 2 Blind spot Insensitive area over optic nerve 3 Fovea Light rays are sharply focused here 4 Optic nerve Transmits nerve impulses 5 Choroid Supplies oxygen and nutrients to the eye via blood vessels in it # Eye part for accommodation Far vision Near vision 6 Ciliary muscles of ciliary body Relaxes and pulls the suspensory ligaments Contracts and relaxes pull on suspensory ligaments 7 Suspensory ligaments Becomes taut and pulls the edge of lens Slackens and relaxes 8 Lens Pulled thin Shrinks and thickens # Supporting eye parts Function 9 Conjunctiva Covers the sclera Secretes mucus for a moist eyeball 10 Sclera Shapes the eye Protects the eye from mechanical injury 11 Cornea Refracts light into eye 12 Aqueous humor Keeps eyeball firm Refracts light into pupil 13 Iris Controls intensity of light that enters 14 Pupil Allows entry of light 15 Vitreous humor Keeps eyeball firm Refracts light onto retina 16 Rectus muscle Allows the eyeball to move (d) describe the pupil reflex in response to bright and dim light Focus Receptors Impulses Light rays from the [nature of object] object are sharply focused on retina Photoreceptors are stimulated and sends nerve impulses to the brain Nerve impulses travel through the optic nerve to the brain for it to interpret the pulses and the person to see the object Eye parts Dim light Bright light Answering instructions Circular muscles of iris Relaxes Contracts Write what contracts first before writing what relaxes Radial muscles of iris Contracts Relaxes Pupil Dilates Constricts Then write the final result: Ensures that Amount of light entering eye Higher Lower the right amount of light enters the eye 56 Consylladated by Lim Ting Jie

57 (e) state that the nervous system brain, spinal cord and nerves, serves to co-ordinate and regulate bodily functions Parts Brain Spinal cord Nerves Roles in coordinating bodily functions Consists of cranial nerves in which impulses are received from the receptor, pain is felt, and an intended action is made, passing this information to the effector by neurones in a cranial reflex Consists of spinal nerves in which impulses are brought to the brain through relay neurones in a cranial reflex for an action to be undertaken, or are carried from sensory to motor neurone by grey matter in a spinal reflex Allow impulses to be brought to the neurones in spinal cord and brain in a reflex action (f) outline the functions of sensory neurones, relay neurones and motor neurones Diagram dorsal root ganglion skin receptor brain cell in grey matter of brain pin white matter of spinal cord relay neurone synapses sensory neurone cell bodies motor neurone effector (muscle) grey matter of spinal cord Neurones Sensory Relay Motor Functions Transmits nerve impulses from the receptors to the central nervous system Transmits nerve impulses from the sensory neurone to the motor neurone to the brain in a cranial reflex Transmits the central nervous system to the effectors to produce a response 57 Consylladated by Lim Ting Jie

58 (g) discuss the function of the brain and spinal cord in producing a co-ordinated response as a result of a specific stimulus in a reflex action Stimulus Reflex Receptors Spinal cord Effects Touching a hot object Cranial reflex (for upper body parts) Heat on object stimulates thermoreceptors in skin Nerve impulses are transmitted by a sensory neurone to the grey matter of spinal cord and then cross a synapse to a relay neurone where they will be transmitted to the brain Person feels the sensation of pain cross another synapse to a motor neurone, then to the biceps muscle effector Biceps muscle contracts Hand withdraws Tap on tendon below the knee cap Spinal reflex (for lower body parts) Tap on knee tendon stimulates stretch receptor Nerve impulses are transmitted by a sensory neurone to the grey matter of spinal cord and then cross a synapse to the motor neurone, then to the knee muscle effector Knee muscle effector contracts Leg jerk forwards (h) define a hormone as a chemical substance, produced by a gland, carried by the blood, which alters the activity of one or more specific target organs and is then broken down by the liver Outline Definition Substance Production Carrier Effect Destruction Chemical substance......produced by an endocrine gland......carried by the blood......alters the activity of one or more specific target organs......and is then destroyed by the liver (i) explain what is meant by an endocrine gland, with reference to the islets of Langerhans in the pancreas Meaning of endocrine gland Ductless glands of internal secretion that secretes hormones directly into the bloodstream... Reference to islets of Langerhans in the pancreas Islets of Langerhans are cells in the pancreas that secrete insulin and glucagon when blood glucose levels are above normal levels and when they are below normal levels respectively... to be distributed around the body through blood... These hormones are transported by blood until they reach body parts they require their effects... to alter the activity of one or more specific target organs Insulin Glucagon Stimulates liver and muscle cells to convert glucose into glycogen for storage Glycogen, fats, amino acids and lactic acid into glucose 58 Consylladated by Lim Ting Jie

59 (j) state the role of the hormone adrenaline in boosting blood glucose levels and give examples of situations in which this may occur Role of the hormone adrenaline in boosting blood glucose levels Speeds up the breakdown of glycogen and glucose in liver and muscles Increases metabolic rate, releasing more energy in respiration Increases rate of heartbeat, resulting in rise in blood pressure, thus oxygen and glucose are carried faster to muscles Constricts arterioles in skin to cause paleness, resulting in more blood and hence more oxygen and glucose to be channeled to muscles Examples of situations Fear Anger Anxiety Stress (k) explain how the blood glucose concentration is regulated by insulin and glucagon as a homeostatic mechanism Receptor-effector Target Effects Feedback Islets of Langerhans of pancreas sense increase of glucose levels and secrete insulin Liver and muscles Increases permeability of cell membranes to glucose (to increase the rate of glucose uptake by cells) Stimulates liver and glucose (to convert excess glucose to glycogen for storage) Increase oxidation of glucose during tissue respiration Negative feedback to the receptor Islets of Langerhans of pancreas sense decrease of glucose levels and secrete glucagon Liver and muscles Stimulates the conversion of glycogen, lactic acid, fats and amino acids to glucose Negative feedback to the receptor (l) describe the signs, such as an increased blood glucose level and glucose in urine, and the treatment of diabetes mellitus using insulin Diabetes mellitus Signs Reasons Treatment Persistently high blood glucose levels Presence of glucose in urine Healing of wounds is slow and difficult Loses weight Kidney tubules reabsorb the maximum amounts of glucose it is able to reabsorb and cannot be stored and utilised by tissue cells Kidney tubules do not have sufficient time to reabsorb glucose during selective reabsorption, and hence excreted in urine As there are no reserves of glycogen, the body is unable to assimilate glycogen and convert it to new protoplasm to heal wounds Oxidises fats instead to produce energy and poisonous ketones that may cause further harm Reserves of glycogen are at minimal levels Daily injection of insulin (supply sugary foods if too much insulin is used, there s too much exercise or too little food, otherwise a coma may result) Constant, consistent regulation of exercising Metformin tablets and insulin injections Use the knowledge gained in this section in new situations or to solve related problems 59 Consylladated by Lim Ting Jie

60 THEME III: CONTINUITY OF LIFE Overview The many aspects of form and function that we have examined in this syllabus can be viewed in the widest context as various adaptations aimed at ensuring reproductive success. Reproduction is vital for the survival of species across generations. In 1953, James Watson and Francis Crick developed the model for deoxyribonucleic acid (DNA), a chemical that had then recently been deduced to be the physical carrier of inheritance. In this section, we examine how genes interact to produce hereditary characteristics in the offspring. This section focuses on understanding the processes involved in the continuity of life and how genetic information is passed from one generation to the next. Extracted from BIOLOGY GCE ORDINARY LEVEL (2014) Syllabus Document 60 Consylladated by Lim Ting Jie

61 12. Reproduction syllacon.weebly.com Content Asexual Reproduction Sexual Reproduction in Plants Sexual Reproduction in Humans Sexually Transmitted Diseases Learning Outcomes: Candidates should be able to: (a) define asexual reproduction as the process resulting in the production of genetically identical offspring from one parent Term Definition In other words Asexual reproduction The process resulting in the production of genetically identical offspring from one parent with no fusion of gametes Mitosis (2n to 2n 2) (b) define sexual reproduction as the process involving the fusion of nuclei to form a zygote and the production of genetically dissimilar offspring Term Definition In other words Sexual reproduction The process resulting in the production of a zygote and genetically dissimilar offspring, involving the fusion of nuclei 1. Meiosis (2n to n 4) 2. Fertilisation (n 2 to 2n) (c) identify and draw, using a hand lens if necessary, the sepals, petals, stamens and carpels of one, locally available, named, insect-pollinated, dicotyledonous flower, and examine the pollen grains under a microscope Typical diagram of a flower Diagram of insect-pollinated Clitoria 61 Consylladated by Lim Ting Jie

62 (d) state the functions of the sepals, petals, anthers and carpels Part Functions Sepal Petal Encloses and protects the other parts of the flower in the bud stage Attracts insects for pollination, brightly coloured Provides a platform for insects to land on for insect pollination Stamen Anther Produces pollen grains and splits open to release them when mature Filament Holds the anther upright Carpel Stigma Receives pollen grains from the anther from the surroundings Secretes sugary fluid to stimulate pollen grains to germinate Style Ovary Connects the stigma to the ovary for the male gamete to travel and meet the female gamete Holds stigma in suitable position to trap pollen grains Encloses one or more ovules containing an ovum (e) use a hand lens to identify and describe the stamens and stigmas of one, locally available, named, wind-pollinated flower, and examine the pollen grains under a microscope Typical diagram of a flower Diagram of wind-pollinated Ischaemum muticum 62 Consylladated by Lim Ting Jie

63 (f) outline the process of pollination and distinguish between self-pollination and crosspollination Term Definition Insect pollination Wind pollination Pollination Transfer of pollen grains from the anther of a flower to the stigma of the same or different flower of the same species The heavy insect lands on standard petal Follows the nectar guide into flower Squeezes past anther to reach nectar Collects pollen on its body while entering Pollen is dusted onto stigma of the same flower by insect when it leaves, or another flower of the same species (when it enters that other flower to collect nectar again) Pendolous filaments hang out of the bracts to expose mature anthers to the wind Dust-like pollen is shaken free upon swaying of filament in wind High surface area feathery stigmas that project out then receives the pollen floating in the wind Differences Self-pollination Cross-pollination Definition Pollen transferred to stigma of same flower or different flower in same plant Pollen transferred to stigma of a flower in another plant of the same species Parent plant Only one is required Two is required Probabilty and location Stigma situated directly below the anthers More likely to occur Stigma situated some distance away from anthers Less likely to occur External factors Independent from external factors Dependent on external factors Wastage Less pollen and energy is wasted More pollen and energy is wasted Qualities Variation Survival Beneficial qualities are more likely to be passed down to the offspring Offspring s genes are similar to parent s Less varieties Lower adaptability Offspring may be weaker, smaller and less resistant to diseases Beneficial qualities may be inherited from both parents Greater genetic variation More varieties produced Higher chance of surviving changes in environment Viable seeds which are capable of surviving longer before germination are produced 63 Consylladated by Lim Ting Jie

64 (g) compare, using fresh specimens, an insect-pollinated and a wind-pollinated flower Differences By insects Reason By wind Reason Nectar Present Food to attract insects Absent To prevent insect pollination Nectar guides Present Guide the insects towards the nectar Absent To prevent insect pollination Petals Present Large, brightly coloured Absent Flowers are small, dull coloured Pollen Fairly abundant, large, rough, usually hairy To cling onto insect bodies easily More abundant, smooth, tiny and light More easily blown about by wind Stigma Small and compact To prevent wind pollination Stamen Non-pendulous To prevent wind pollination Large and feathery, protrudes out Pendulous filaments, long protruding anthers Large surface area to trap pollen Easily shaken out from anthers Scent Fragrant or sweetsmelling Attracts insects No scent To prevent insect pollination (h) describe the growth of the pollen tube and its entry into the ovule followed by fertilisation (Production of endosperm and details of development are not required) # Acroynm Stages Description 1 S Sugary fluid Mature stigma secretes sugary fluid 2 E Enzymes Pollen tube secretes enzymes 3 M Micropyle Pollen tube enters the micropyle 4 F Fertilisation Tip of pollen tube absorbs sap Pollen grains germinate Pollen tube grows out from each grain Surrounding tissues of stigma and style are digested Tube penetrates through the style Generative nucleus divides, forms two male gametes Pollen tube nucleus disintegrates Bursts to release male gametes One male gamete fuses with ovum to form zygote 5 E Embryo Zygote divides Develops into embryo formed in the seed 64 Consylladated by Lim Ting Jie

65 (i) identify on diagrams of the male reproductive system and give the functions of: testes, scrotum, sperm ducts, prostate gland, urethra and penis Diagrams of male reproductive system # Part Functions 1 Testis Produces sperms and male sex hormones like testosterone 2 Scrotum Contains testes lying outside main body cavity Provides sperms with a suitable temperature (slightly lower than body temperature) for proper development 3 Sperm duct Conducts sperms from the testis to seminal vesicle to be stored temporarily before being released to urethra 4 Prostate gland Secretes a slippery alkaline fluid with Cowper s gland and seminal vesicle It contains nutrients and enzymes to nourish sperms and allow sperm motility 5 Urethra Conducts urine and semen out of the body separately, with sphincter muscle to prevent urine from coming out during ejaculation 6 Penis Deposits semen into the female reproductive system through the vagina after blood fills the erectile tissue, turning it erect 65 Consylladated by Lim Ting Jie

66 (j) identify on diagrams of the female reproductive system and give the functions of: ovaries, oviducts, uterus, cervix and vagina Diagrams of female reproductive system # Part Functions 1 Ovary Produces ova and releases them when mature Produces female sex hormones 2 Oviduct Conducts mature egg from the ovary into the uterus through funnel-like opening Location from egg fertilisation 3 Uterus Provides a suitable environment for foetal development during pregnancy Contains smooth muscles in the uterine wall which contract to expel the foetus during birth 4 Cervix Keeps the opening of the uterus closed to maintain pregnancy Dilates during birth to allow the foetus to pass out of the uterus during birth 5 Vagina Allows flow of blood out of the uterus during menstruation Receives semen during sexual intercourse Allows passage of foetus out of the uterus during birth 66 Consylladated by Lim Ting Jie

67 (k) briefly describe the menstrual cycle with reference to the alternation of menstruation and ovulation, the natural variation in its length, and the fertile and infertile phases of the cycle with reference to the effects of progesterone and estrogen only # Stages of menstrual cycle Description of stage Duration Nature of cycle 1 Menstruation Uterine lining breaks down and flows from the uterus out of the body by menstrual flow through the vagina 2 Repair and growth of uterine lining Ovaries secrete oestrogen to ensure that the uterine is vascularised, thickened and well supplied with blood vessels Days 1 to 5 Days 6 to 13 Alternates between menstruation and ovulation 3 Ovulation Ova are produced during the fertile period Day 14 4 Ovulation inhibited Progesterone and oestrogen maintain the thickness of uterine lining and further supply blood vessels with blood capillaries Days 15 to 28 Outcome of fertilisation Egg Hormones Uterine lining Role of placenta Not successful Egg breaks down Progesterone is not secreted Uterine lining breaks down Cycle repeats Not applicable Successful Zygote develops into embryo Secretion of progesterone and oestrogen sustained by ovary and then placenta later on Embryo embeds itself in uterine lining Placenta develops from the embryonic villi (embedded in uterine lining) Secretion of hormones by the ovary stops after placenta is able to start secreting them Aspect of cycle Average Range Remarks Natural variation in its length 28 days Anomalies of 21 to 33 days May take up to 3 years for periods to be regular Stress, tiredness, illnesses, and an unbalanced diet or malnutrition, may alter or stop the menstrual cycle Aspect of cycle Gamete Lifespan High presence in uterus Conditions required Fertile and infertile phases of the cycle Sperms 2 to 3 days Ejaculation starts on day 11 Uterine lining must have been repaired by then Ova 1 to 2 days Days 14 to 16 Ovulation must have occurred on day Consylladated by Lim Ting Jie

68 (l) describe fertilisation and early development of the zygote simply in terms of the formation of a ball of cells which becomes implanted in the wall of the uterus syllacon.weebly.com # Acronym Stages Description 1 P Penetration Acrosome of sperm releases enzymes 2 F Fertilisation One sperm nucleus enters 3 I Implantation Cilia and peristaltic movements sweep zygote along oviduct 4 P Placenta Villi with blood capillaries grow from embryo to uterine Part of the egg membranes are broken down Nucleus fuses with egg to form a diploid zygote Other sperms eventually die Zygote divides by mitosis to form a ball of cells Embryo reaches uterus after 5 days from fertilisation Embeds in uterine lining after 2 days Placenta forms after villi grows fully Embryo separates from placenta Umbilical cord connects the embryo to placenta 5 F Fetus develops All major organs are formed, 10 to 12 weeks after fertilisation (m) state the functions of the amniotic sac and the amniotic fluid Parts Amniotic sac Functions Encloses the fetus in the amniotic cavity containing amniotic fluid Amniotic fluid Cushions Shock Injury Lubrication Movement Supports and cushions fetus before birth Absorbs shock if mother falls Protects fetus against physical injury due to its incompressibility Lubricates and reduces friction in the vagina or birth canal Allows fetus to move freely during growth (n) describe the function of the placenta and umbilical cord in relation to exchange of dissolved nutrients, gases and excretory products (Structural details are not required) Parts Placenta Umbilical cord Oxygen and dissolved substances Excretory products Antibodies Progesterone Carbon dioxide and metabolic waste products by arteries Oxygen and food substances by veins Functions Allows oxygen and dissolved substances to diffuse from the mother's blood into the fetus blood Allows excretory products such as urea and carbon dioxide to diffuse from the fetus blood to mother s blood Allows protective antibodies to diffuse from the mother s blood into the fetus' blood which protect the fetus against certain diseases Produces progesterone which maintains the uterine lning in a healthy state during pregnancy Transport deoxygenated blood and metabolic waste products from the fetus to the placenta through 2 umbilical arteries Transport oxygenated blood and food substances from the placenta to the fetus through 1 umbilical vein 68 Consylladated by Lim Ting Jie

69 (o) discuss the spread of human immunodeficiency virus (HIV) and methods by which it may be controlled Means of spread of HIV Methods of its control In general Sex Hypodermic needles Blood transfusion Sexual intercourse with an infected person Sharing of hypodermic needles, if not sterilised properly, like acupuncture and ear piercing Blood transfusion from an infected person No sex Condom Drug abuse Dispose Contamination Keep to one sex partner or do not have sex During sex, males should wear a condom to protect themself in case their partner has HIV Do not abuse drugs, as drug addicts usually share needles and chances of getting HIV is higher Use sterilised or disposable needles always Do not share instruments that can break the skin and may be contaminated with blood Transmission can only be through bodily fluids and when infected blood contaminates the new victim's blood Transmission will not occur by surface level contact or flow as it does not enter the skin Pregnancy Infected mothers may transfer the virus to fetus through umbilical cord N.A. N.A. Use the knowledge gained in this section in new situations or to solve related problems 69 Consylladated by Lim Ting Jie

70 13. Cell Division syllacon.weebly.com Content Mitosis Meiosis Learning Outcomes: Candidates should be able to: (a) state the importance of mitosis in growth, repair and asexual reproduction # Importance Description of importance of mitosis Examples 1 Growth Mitosis allows for the growth and development of a multicellular organism 2 Repair Mitosis allows for the repair or replacement of worn-out parts of the body Development of a fertilised egg into an adult human being Sealing up of wounds from injuries Replacement of dead and worn-out cheek cells may be shed during teeth brushing and mouth rinsing 3 Asexual reproduction Mitosis is also the basis for asexual reproduction Enable shoots and roots to develop in storage organs (e.g. bulbs) (b) explain the need for the production of genetically identical cells and fine control of replication # Reasons for production of genetically identical cells Description of reasons 1 Growth Mitosis allows for the growth and development of a multicellular organism 2 Repair Mitosis allows for the repair or replacement of worn-out parts of the body 3 Asexual reproduction Mitosis is also the basis for asexual reproduction # Reasons for fine control of DNA replication Related mechanism in control of DNA replication 1 Ensures that cells produced are genetically identical 2 Ensures that 2 sets of identical genetic material is present before cell division 3 Prevents abnormal development of the embryo Chromosomes of parent nucleus are already duplicated before mitosis begins Arrangement of chromosomes at the equator during metaphase ensures that chromosomes are shared equally between the 2 daughter cells If there are errors in DNA replication, they will be transmitted to the daughter cells May lead to harmful changes to genes and affect how the cells function Embryo may not develop normally 4 Prevents cancer If there are errors in DNA replication, this may cause cells to lose the ability to control the way they divide and their normal functions 70 Consylladated by Lim Ting Jie

71 (c) identify, with the aid of diagrams, the main stages of mitosis (e) identify, with the aid of diagrams, the main stages of meiosis # Stage Mitosis Meiosis I Meiosis II 1 I Interphase 2 P Prophase microtubules (spindle fibres) centromere nuclear envelope centriole a pair of homologous chromosomes 3 M Metaphase equator pole 4 A Anaphase separated chromosome 5 T Telophase chromosome uncoiling nuclear membranes nuclear membrane reforms nuclear membranes 6 C Cytokinesis Differences Mitosis Meiosis Definition Daughter cells Pairing Cell division by which one single diploid parent result in the production of two daughter cells All are identical the original parent cell Pairing of homologous chromosomes do not occur Cell division by which one single parent diploid cell divides to produce four haploid cells Gametes with half the diploid chromosomes in parent and may contain variations from parent cell Homologous chromosomes pair up at Prophase I Crossing over Does not occur May occur Divisions One nuclear division Two nuclear divisions for a reduction division 71 Consylladated by Lim Ting Jie

72 (d) state what is meant by homologous pairs of chromosomes Term Meaning Properties Similarities Differences Homologous pairs of chromosomes Two chromosomes that pair along their whole length during synapsis Same shape, genes and length with genes found on the same loci Alleles of each trait may not be the same (f) define the terms haploid and diploid, and explain the need for a reduction division process prior to fertilisation in sexual reproduction Term Diploid Haploid Reduction division Fertilisation Definition The number of chromosomes present in a normal body cell of a species of an organism The number of chromosomes present in a gamete of a species of organism, containing half the number of chromosomes as the normal body cell The process by which one diploid parent nucleus divides to form four haploid daughter nuclei, where each daughter nucleus contains half the number of chromosomes as the original nucleus in the parent cell (This is because of the separation of homologous chromosomes during Anaphase I) The process by which gametes fuse to produce a zygote which restores the diploid number of chromosomes Need for reduction divison prior to fertilisation A reduction division prevents doubling of the number of chromosomes in each successive generation The number of chromosomes after each successive generation will thus remain diploid (g) state how meiosis and fertilisation can lead to variation Processes Explanation Meiosis Crossing over Independent assortment Two non-sister chromatids of homologous chromosomes may cross and twist around each other at a chiasma Coiling causes exchange of chromatids or crossing over New combinations of genes along chromosome are produced Four chromosomes randomly pair up with one other Two assorted pairs of chromosomes form, each in every pair face opposite poles of the cell New combinations of genes are produced after meiosis I Fertilisation Fertilisation involves the fusion of a male gamete and female gamete These gametes have been produced by meiosis which crossing over may have occurred As new combinations of genes are produced, the new organism may vary from parents Use the knowledge gained in this section in new situations or to solve related problems 72 Consylladated by Lim Ting Jie

73 14. Molecular Genetics syllacon.weebly.com Content The Structure of DNA The Role of DNA in Protein Synthesis Genes Genetic Engineering and Medical Biotechnology Learning Outcomes: Candidates should be able to: (a) outline the relationship between DNA, genes and chromosomes Structure Description Diagram Gene DNA Chromosome A gene is a sequence of nucleotides containing genetic information used to make proteins DNA (deoxyribonucleic acid) consists of two parallel strands of nucleotides twisted around each other in a double helix Each strand of DNA is made up of many genes A chromosome is made of condensed chromatin threads, which consists of DNA wrapped with proteins (b) state the structure of DNA in terms of the bases, sugar and phosphate groups found in each of their nucleotides Components of a nucleotide Description Polynucleotide formation Nitrogenous base Adenine or Cytosine or Guanine or Thymine Nucleotides can be joined together to form Deoxyribose sugar Form the sugar-phosphate backbone in a polynucleotides polynucleotide Phosphate group Diagrams Nucleotide Polynucleotide (section) 73 Consylladated by Lim Ting Jie

74 (c) state the rule of complementary base pairing Rule TA rule CG rule Description of the rule to form pairs of bases Thymine always hydrogen bonds with adenine to form complementary bases Cytosine always hydrogen bonds with guanine to form complementary bases (d) state that DNA is used to carry the genetic code, which is used to synthesise specific polypeptides (details of transcription and translation are not required) Molecules involved in protein synthesis DNA Gene RNA Role DNA carries a gene that occupies a locus along a chromosome A gene carries a genetic code that is used to synthesise specific polypeptides It controls exactly how a particular protein is made in the cell through transcription and translation RNA (ribonucleic acid) is a temporary molecule to transfer information from DNA to molecules directly involved in protein synthesis It contains uracil instead of thymine, which also bonds with adenine only (e) state that each gene is a sequence of nucleotides, as part of a DNA molecule Term Gene Description Each gene is a sequence of nucleotides as part of a DNA molecule The sequence of nucleotides stores a message that determines how a protein should be made (f) explain that genes may be transferred between cells. Reference should be made to the transfer of genes between organisms of the same or different species transgenic plants or animals Term Definiton Method Genetic engineering Technique used to transfer genes from one organism to another Genes are extracted ( cut off ) from the cells of one organism and inserted into the cells of another organism Examples of transfer Between different species Between same species Gene transferred Soil fungus Myrothecium verrucaria Healthy gene Desired function of gene Product To produce cyanamide hydratase enzyme that converts cyanamide to urea, a harmless source of nitrogen This process produces transgenic plants since it is between different species To replace genes of lung disease cystic fibrosis when excessive mucus produced blocks the respiratory system, causing breathlessness This process of gene therapy does not produce transgenic animals since it is between the same species 74 Consylladated by Lim Ting Jie

75 (g) briefly explain how a gene that controls the production of human insulin can be inserted into bacterial DNA to produce human insulin in medical biotechnology # Steps Procedures Key molecules 1 Isolate the desirable human gene 2 Plasmid preparation 3 Join desirable gene to the plasmid 4 Insertion of gene into E.coli bacteria 5 Plasmid multiplication Restriction enzyme cuts out the gene for producing human insulin at 2 specific points from the insulin DNA, forming a single strand sequence of bases on each side of the gene Same restriction enzyme cuts open the plasmid DNA (vector from a bacterial cell), forming a single strand sequence of bases complementary to bases on the sides of insulin DNA DNA ligase joins the cut ends of the plasmid DNA and insulin DNA by complementary base pairing of both ends to form the plasmid containing the human insulin gene Mix the plasmid with E.coli bacteria and heat shock is carried out temporarily Transgenic bacteria makes copies of the plasmid when they reproduce when dividing Restriction enzyme Restriction enzyme DNA ligase Electric shock Division (h) discuss the social and ethical implications of genetic engineering, with reference to a named example Prior knowledge of named example Example Synthesis Significance Bt corn (a plant) Bt gene from Bacillus thuringiensis bacteria is inserted into corn Bt gene produces a protein that is lethal to pests of the corn, but not lethal to humans and other vetebrates This reduces agricultural loss due to pests attacks Knowledge required to respond to question Social implications Ethical implications Threatens the safety of the environment Genetically modified crops may be carried by wind to other places and grow quickly, potentially establishing themselves as weeds Pollen grains from these plants may also fertilise wild relatives to form superweeds and compete with the natural species Making a staple crop more resistant under marginal conditions may be a potential boon for Third World agriculture as richer countries benefit at the expense of poorer countries World food production may also be dominated by a small number of large companies with the technical know-how in the long run, leading to rising income inequality Use the knowledge gained in this section in new situations or to solve related problems 75 Consylladated by Lim Ting Jie

76 15. Inheritance syllacon.weebly.com Content The Passage of Information from Parent to Offspring The Nature of Genes and Alleles, and their Role in Determining the Phenotype Monohybrid Crosses Variation Natural and Artificial Selection Learning Outcomes: Candidates should be able to: (a) define a gene as a unit of inheritance and distinguish clearly between the terms gene and allele Terms Definitions Examples Gene [Inheritance, for this chapter] A unit of inheritance and a section of a DNA that codes a particular trait [Molecular Genetics] A sequence of nucleotides as part of a DNA molecule Height of pea plants Colour of flowers Allele Alternative forms of the same gene Tall/short, Purple/white (b) explain the terms dominant, recessive, codominant, homozygous, heterozygous, phenotype and genotype Terms Definitions Examples Phenotype Visible characteristics of an organism Black fur on rabbits is a phenotype represented by BB and Bb genotypes Genotype Homozygous Heterozygous Dominant Recessive Genetic makeup of an organism to determine phenotype Two copies of an allele controlling an organism s trait are similar Two alleles controlling an organism s trait are different Allele which gives same phenotype in both homozygous and heterozygous conditions Allele which expresses itself only in the homozygous condition and does not express itself in the heterozygous condition BB, Bb, bb are genotypes that determine the phenotype of either black fur or white fur BB (Homozygous dominant) bb (Homozygous recessive) Bb (Heterozygous) B is the dominant allele (capital letter) BB and Bb represent the same phenotype b is the recessive allele (small letter) bb shows a different phenotype from BB and Bb Codominance Condition in which both alleles exert equal effects in the offspring s trait When I A is codominant to I B, Blood Group AB is the phenotype If RR shows red and rr shows white, then Rr represents pink 76 Consylladated by Lim Ting Jie

77 (c) predict the results of simple crosses with expected ratios of 3:1 and 1:1, using the terms homozygous, heterozygous, F1 generation and F2 generation Punnett square (gametes bolded) B B B BB BB B BB BB B b B BB Bb B BB Bb B b B BB Bb b Bb bb B b b Bb bb b Bb bb b b b bb bb b bb bb Offspring phenotypic ratio 1 1 1:1 (if codominant) 1:3 1:2:1 (if codominant) 1:1 1 F1 and F2 generation The F1 generation of 2 parents are the offsprings of the parents The F2 generation of 2 parents are the offsprings of the F1 generation above (d) explain why observed ratios often differ from expected ratios, especially when there are small numbers of progeny Explanation to learning outcome Observed ratios often differ from expected ratios as expected ratios are based mainly on chance and probability This is especially when there are small numbers of progeny (offspring) when the actual number of progeny would be more unlikely to match the expected number precisely as chances of the offspring to match its expected characteristic is lower than expected (e) use genetic diagrams to solve problems involving monohybrid inheritance. (Genetic diagrams involving autosomal linkage or epistasis are not required) Example of genetic diagram (must be based on question asked) Organism Pink flower Pink flower Parental Phenotype Pink colour X Pink colour Parental Gentoype Aa X Aa Gametes (must be circled) Offspring Genotype (from punnett square) A a A a AA Aa Aa aa Offspring Phenotype Purple colour Pink colour Pink colour White colour 77 Consylladated by Lim Ting Jie

78 (f) explain co-dominance and multiple alleles with reference to the inheritance of the ABO blood group phenotypes A, B, AB, O, gene alleles I A, I B and I O Phenotype Genotype Allele relationship Exam response Blood Group A Blood Group B I A I A or I A I O I B I B or I B I O I A dominant over I O I B dominant over I O Explain all sides, e.g. if asked to determine that an allele is dominant, explain why being dominant would cause the result and Blood Group AB I A I B I A is codominant to I B why the result will be different if the allele is Blood Group O I O I O Nil recessive (g) describe the determination of sex in humans XX and XY chromosomes Chromosome number in humans Each cell in humans has 23 pairs of chromosomes It consists of 22 pairs of autosomes and 1 pair of sex chromosomes Phenotype Genotype (in sex chromosomes) Allele relationship Male XY Y dominant over X Female XX (h) describe mutation as a change in the structure of a gene, such as in sickle cell anaemia, or in the chromosome number, such as the 47 chromosomes in the condition known as Down syndrome Mutation Example of Gene mutation Example of Chromosome mutation Example Sickle cell anaemia Down Syndrome Details Inherited disease Happens by chance How it happens Effects Special cases Someone with sickle cell anaemia produces haemoglobin S instead of haemoglobin A It is a homozygous recessive disease, aa Stiff and sticky to form clumps in blood vessels which may obstruct blood flow Lead to serious infections Organ damage Heterozygous humans, Aa, without the disease: May pass on to the next generation Can survive better in a malaria prone area Mutation causes one gamete from either the male or female to have 2 copies of chromosome 21 When it fuses with the normal gamete of the other sex, the zygote will have 3 copies of chromosome 21, resulting in 47 chromosomes instead of the normal 46 Low resistance to disease Mental retardation Stunted growth Older mothers have a higher chance of giving birth to a child with the disease than younger ones 78 Consylladated by Lim Ting Jie

79 (i) name radiation and chemicals as factors which may increase the rate of mutation Mutation catalysts Radiation Chemicals UV light, Gamma radiation Examples Mustard gas, Formadehyde, Ferrous and manganous salts (j) describe the difference between continuous and discontinuous variation and give examples of each Term Variation Definition Differences in traits between individuals of the same species Differences Continuous variation Discontinuous variation Intermediate characteristics Yes No Distinct phenotype No Yes (to the extremes) Causes of variation Genes Yes Yes Environment Yes No Number of genes Controlled by a few genes Controlled by a single gene usually Additive effect of genes Yes No (k) state that competition which arises from variation leads to differential survival of, and reproduction by, those organisms best fitted to the environment Term Natural selection Mechanism Variation in a population means that some organisms are more well fitted to the environment, which may result in competition This leads to those organisms best fitted to the environment to survive better (i.e. differential survival) which allows more of these organisms to reproduce than those less fitted (i.e. differential reproduction) 79 Consylladated by Lim Ting Jie

80 (l) give examples of environmental factors that act as forces of natural selection syllacon.weebly.com Explanation Predation example Droughts example Organism Rabbits Finches Situation Change in environment Type(s) at selective advantage Mutation took place and produced varieties of traits like coat colour and size of rabbit variety When a predator species start to thrive, rabbits of different varieties start move away from their dangerous habitat at risk of predation in search of other suitable habitats Type with light colour of fur coat and is bigger sized moved to an open plain and to escape predation Appearance Adaptation There was a natural variation in the sizes of the beaks of the finches on the Galápagos island Plants on the island produce either big, hard and dry seeds from trees or small, soft and moist seeds from vines and creepers When a drought occured for a period of a few years, many vines died due to lack of moisture and supply of small and moist seeds decreased sharply, causing relatively more seeds from trees to be available Finches with bigger beaks survived the drought better as they were able to crack the harder seeds better and therefore better able to source for food Light colour Long hind legs Long ears Upright position Camouflages well Escape from predators Detect predators See further to source food Type with dark fur colour and is smaller sized moved to a dense forest and to escape predation Appearance Dark colour Small size and able to crouch Adaptation Camouflages well Less detectable as they are able to hide among logs Type(s) at disadvantage One-sided survival Time passes Domination The type of rabbit with an appearance that makes it easy to spot by predators or rabbits that travel to a habitat that does not favour escape from predation Light coated, bigger sized rabbits in open plains and dark coated, smaller sized rabbits in dense forests had the selective advantage and more of them survived predation to adulthood These rabbits reproduced and started to have offsprings at a faster rate than other species The big light coated rabbits and small dark coated rabbits dominated the population of their repective habitats in the next generation Finches with smaller, weaker beaks died off during the drought as supply of soft seeds dropped sharply, food was not readily available Finches with bigger beak size had the selective advantage and more of them survived to adulthood These finches reproduced and started to have offspring at a collectively faster rate than other species Finches with bigger beaks dominated the population in the next generation 80 Consylladated by Lim Ting Jie

81 (m) explain the role of natural selection as a possible mechanism for evolution syllacon.weebly.com Term Definition Link to evolution Natural selection Mechanism that brings about adaptation to the environment and evolution Different variants are selected for or against by different environment factors that act as selective pressures Organisms with favourable traits that are genetically determined will survive better and reproduce Offspring will inherit their traits over time, increasing the frequency of alleles for favourable traits and decreasing the frequency of alleles for nonfavourable traits (n) give examples of artificial selection such as in the production of economically important plants and animals Production Improving plants by hybridisation Improving animals by inbreeding Procedure To cultivate a variety of wheat that has two main desirable traits, two parents each with one of the two traits is crossed Some new hybrids will have preferred combination of genes from both parents (desirable traits) The hybrid is propagated by vegatative means to prevent any repeats of hybridisation for the next generations as offspring is not identical Similar process of hydrisation as above for new breeds of animals (e.g. cattle) Mating carried out instead of crossing Inbreeding maintains the improved breed by breeding among closely related individuals Differences Natural selection Artificial selection Definition Varieties Nature selects for organisms with favourable genes and traits that help them survive unique habitats Produced by mutations Produced by selective breeding by humans Occurence When natural environment conditions change When humans select organism varieties to suit their needs, Importance Possible mechanism for evolution, which is the process by which present forms of living organisms have arisen producing more diversity from simpler ancestral forms Use the knowledge gained in this section in new situations or to solve related problems 81 Consylladated by Lim Ting Jie

82 THEME IV: MAN AND HIS ENVIRONMENT Overview All living organisms are part of a complex network of interactions called the web of life. This section focuses on the interrelationships among living things. These include two major processes. The first is the cycling of nutrients, as illustrated by the carbon cycle. The second major process is the flow of energy from sunlight to organisms further down the food chain. Human activities can upset natural ecosystems, causing permanent damage not just to local environments but also the global environment. As a part of this environment, humans must show a sense of responsibility for its maintenance. Extracted from BIOLOGY GCE ORDINARY LEVEL (2014) Syllabus Document 82 Consylladated by Lim Ting Jie

83 16. Organisms and their Environment syllacon.weebly.com Content Energy Flow Food Chains and Webs Carbon Cycle Effects of Man on the Ecosystem Environmental Biotechnology Conservation Learning Outcomes: Candidates should be able to: (a) briefly describe the non-cyclical nature of energy flow Non-cylical Heat energy Supply Respiration Excretion, egestion Light energy Energy does not flow in a cycle Heat energy cannot be recycled nor used to do work Energy needs to be constantly supplied to the ecosystem Carbon dioxide is produced for photosynthesis Carbon dioxide is produced when these waste products are decomposed Combines with chlorophyll to release chemical energy (b) explain the terms producer, consumer and trophic level in the context of food chains and food webs Term Producer Consumer Trophic level Explanation Organisms that convert energy from the Sun into chemical energy and store it as food during photosynthesis Organisms that obtain energy by feeding on other organisms Stage of a food chain (e.g. producers are always located at the first trophic level) (c) explain how energy losses occur along food chains, and discuss the efficiency of energy transfer between trophic levels How energy is lost Amount of energy lost Efficiency of energy transfer Uneaten body parts Faeces as waste products Excretory products, undigested matter egested Heat loss during respiration We usually assume 90% of energy is lost when energy is transferred to the next trophic level 10% is passed down Short food chains are more efficient in energy transfer Less energy is lost to the environment along the food chain More energy is available to the final consumer 83 Consylladated by Lim Ting Jie

84 (d) describe and interpret pyramids of numbers and biomass Term Pyramid of numbers Pyramid of biomass Explanation To compare the number of organisms present in each trophic level at a particular time To compare the mass of organisms present in each trophic level at a particular time Pyramid of numbers Pyramid of biomass If organisms at the top If organisms at the bottom Organisms at the bottom are greater in numbers are smaller in numbers are always smaller in numbers compared to those in the previous trophic level compared to those in the next trophic level compared to those in the next trophic level they are likely parasitic they are likely to be a producer They also have higher rates of reproduction and hence small in size that is large in size (e.g. a tree) Diagrams Pyramid of numbers Pyramid of biomass 84 Consylladated by Lim Ting Jie

85 (e) describe how carbon is cycled within an ecosystem Removal of carbon dioxide Release of carbon dioxide Photosynthesis Carbon compounds Animals Plants absorb CO 2 from air to manufacture carbohydrates Respiration When organisms respire, C compounds are broken down and carbon dioxide is released to the environment as a byproduct Glucose is converted to other C compounds like fats, amino acids and proteins Decay The bodies of dead organisms decay Animals feed on plants and C compounds enter their bodies and are broken down into simple substances by decomposers Fossil fuels When organisms die, C compounds can be preserved in fossil fuels as coal, natural gas and oil Combustion When fossil fuels undergo combustion, C compounds preserved are broken down and carbon dioxide is released to the environment Diagram of carbon cycle Inferences Energy flow is non-cyclical Carbon flow is cyclical 85 Consylladated by Lim Ting Jie