B2 Revision Pack Please keep this pack with you

Transcription

1 Name: B2 Revision Pack Please keep this pack with you Follow all the steps below... 1) Practice all the maths questions (10%+ of the exam is maths!) Maths and Science Skills Questions Foundation Questions - Standard Questions Higher Questions - 2) Practice Quiz short answer questions (included in this pack) 3) Practice QWC questions long answer questions (included in this pack) 4) Practice all the Popplet questions B2 1 Cells and Simple Cell Transport B2 2 Tissues, Organs and Organ Systems B2 3 Photosynthesis B2 4 Organisms and Their Environment B2 5 Proteins - Their Functions and Uses B2 6 Aerobic and Anaerobic Respiration B2 7 Cell Division and Inheritance B2 8 Fossils and Speciation Foundation Questions - Standard Questions - Higher Questions Foundation Questions - Standard Questions - Higher Questions Foundation Questions - Standard Questions - Higher Questions Foundation Questions - Standard Questions - Higher Questions Foundation Questions - Standard Questions - Higher Questions Foundation Questions - Standard Questions - Higher Questions Foundation Questions - Standard Questions - Higher Questions Foundation Questions - Standard Questions - Higher Questions Our Predictions: Variables, graphs, means, anomalies, writing methods, improvements, reliability, accuracy etc. Cells animal, plant, bacteria, yeast etc. Photosynthesis and plants, e.g. factors affecting photosynthesis, organisation in plants etc. Proteins (everything) Enzymes (Possible 6 mark) Inheritance of disorders and genetics Drawing genetic diagrams to show inheritance Sampling methods, e.g. how to us a transect (see the model QWC question inside) + using quadrats for random sampling, improving accuracy and reliability of results, how to take a random sample etc. Anything looking at advantages/disadvantages don t forget to write a conclusion.

2 PRACTICE QUIZ B2.1_Cells and Simple cell transport B2.1.1 Cells and cell structure 1. What are the main parts of animal cells? Nucleus, cytoplasm, cell membrane, mitochondria, ribosomes 2. Which parts of a cell are found in plant cells but not animal cells? Cell wall, chloroplasts, permanent vacuole 3. Name the parts of bacterial cells? Cytoplasm, ribosomes, genes (that are not a distinct nucleus) and a cell membrane surrounded by a cell wall. 4. Name the parts of yeast cells contain? Nucleus, cytoplasm and a membrane surrounded by a cell wall. 5. What is the function of a nucleus of a cell? To control the activities of the cell and to store the genetic information. 6. If a cell has adapted to do a particular function, what is it said to be? Specialised 7. What is the function of cytoplasm? To provide a place for most of the chemical reactions to take place. 8. What is the function of a cell membrane? To control the passage of substances into and out of the cell. 9. What is the function of mitochondria? To provide a place for most of the energy in respiration to be released. 10. Where does protein synthesis in the cell happen? Ribosomes 11. Which feature do plant cells have which help them to strengthen their cells? They have cell walls made of cellulose 12. What is the function of the chloroplasts? They absorb light energy to make glucose (carry out photosynthesis) 13. What is found inside the permanent vacuole of plant cells? Cell sap 14. What is important about the genetic information in a bacterial cell? It is not inside a distinct nucleus

3 15. What part is missing from a red blood cell? A nucleus 16. Name two features of a sperm cell. Tail, lots of mitochondria, enzymes in the head, single set of chromosomes 17. What is the function of the goblet cell? Produce mucus 18. Where in the body do you find goblet cells? Digestive system and lungs 19. Why do cilia and sperm have lots of mitochondria? They move a lot so need lots of energy B2.1.2 Dissolved substances 1. How do dissolved substances move in and out of cells? Through cell membranes by diffusion 2. What is the definition of diffusion? Diffusion is the spreading of the particles of a gas or of any substances in solution from a region of higher concentration to a region of lower concentration. 3. What will affect the rate of diffusion? Temperature and concentration 4. What is a concentration gradient? A difference in concentration between two areas next to each other. 5. Name two locations in the body where diffusion is important. Lungs and small intestines 6. Which important gas passes through cell membranes into cells? Oxygen B2.2_Tissues, organs and organ systems B2.2.1 Animal organs 1. What does multicellular mean? An organism with a number of cells which work together to carry out functions. 2. What is a tissue? A group of cells with similar structure and function which work together to carry out a particular function e.g. muscle 3. What is an organ? Different types of tissue which work together to carry out a function e.g. the heart.

4 4. What is an organ system? A group of organs all working together to carry out a particular function. 5. What is the function of muscular tissue? To contract and relax to bring about movement. 6. What is glandular tissue? A tissue which produces substances such as enzymes and hormones (e.g. ovary) 7. What is epithelial tissue? A tissue which covers some parts of the body (lining of the body) 8. Which 3 main tissues does the stomach contain? Muscular tissue (to churn food), glandular tissue (to produce digestive juices) and epithelial tissue (to cover the outside and inside of the stomach) 9. Complete the following table for parts of the digestive system, name the parts. Part(s) Stomach Liver Large intestine Small intestine Pancreas/ salivary glands Function Digests food Produces bile Absorbs water/ produces faeces Digest and absorb soluble food Produce digestive juices B2.2.2 Plant organs 1. What are the 4 main organs of plants? Roots, stems, flowers and leaves 2. What tissue are plants covered in? Epidermal 3. Which tissue is responsible for carrying out most photosynthesis? Mesophyll 4. Which tissue transports water around the plant? Xylem 5. Which tissue transports sugars around the plant? Phloem

5 6. What tissue allows gases in and out of a plant leaf? Stomata 7. Label parts A E. A Waxy layer B Upper epidermis C Palisade cell D Spongy Cell E Stomata B2.3.1 Photosynthesis 1. What are the reactants needed for photosynthesis? Water and Carbon dioxide 2. What are the products of photosynthesis? Glucose and oxygen 3. Which type of energy is essential for photosynthesis to take place? Light energy 4. Which organelle (part of a cell) carries out photosynthesis? Chloroplast 5. What is the name of the green substance which captures light energy (and is found in chloroplasts) to enable photosynthesis? Chlorophyll 6. Where does the water, required by plants, come from? The soil 7. What three factors can limit the rate of photosynthesis? Light, CO2, Temperature 8. How is glucose used by plants and algae? (There are a number of ways.) Used in respiration, used to produce fat, oil, cellulose (which strengthens cell walls) and proteins 9. What else do plants need to absorb from the soil to produce proteins? Nitrate ions

6 10. What do plants store starch as? Insoluble starch 11. List three things you can do in a greenhouse to increase growth. Artificial light allows photosynthesis to continue Heating allows photosynthesis to continue at an increased rate heater can also give off extra carbon dioxide released. B2.4.1 Distribution of organisms 1. Which six physical factors affect organisms? Temperature, availability of nutrients, amount of light, availability of water, availability of oxygen and availability of carbon dioxide 2. What is a quadrat? These are square frames, used to mark off specific areas of ground 0.5m X 0.5m 3. Which two methods can be used to collect quantitative data on the distribution of organisms? Random sampling using quadrats and sampling along a transect 4. How can you make sure you place the quadrats at random? Use a calculator to generate random numbers. 5. Why should a large sample size be used when sampling data? To make the results more valid (you can calculate a mean, identify anomalous results, look for patterns, etc) 6. What is another term for non living factors? Abiotic 7. What is another term for living factors? Biotic B2.5 Proteins their functions and uses B2.5.1 Proteins/B2.5.2 Enzymes 1. Which molecule are proteins made from? Amino acids 2. What happens to the long chains formed by these molecules? They are folded up into a specific shape 3. What do proteins act as? Structural components of tissues (e.g. muscles), hormones, antibodies and catalysts.

7 4. What do catalysts do? They speed up chemical reactions. 5. What are biological catalysts called? Enzymes 6. Which type of molecule are enzymes made from? Proteins 7. What property of enzymes is vital for its function? The shape of the enzyme molecule 8. What do high temperatures do to enzymes? The shape of the enzyme molecule 9. What other factor is important for enzymes to function correctly? ph 10. What does denatured mean? When the active site of an enzyme changes shape. 11. Which two enzymes are present in biological detergents (washing powders)? Proteases and lipases 12. How does having enzymes in biological detergents help them to perform better? They are more effective at low temperatures (high temperatures will denature the enzymes in them) 13. How are proteases used in industry? To pre digest baby food (making it easier for babies to digest their food) 14. How is isomerase used in industry? To convert glucose syrup into fructose syrup, which is much sweeter, and therefore can be used in smaller quantities in slimming food B2.5.2 Enzymes 1. Where are digestive enzymes produced? By specialised cells in glands and the lining of the gut. 2. What is the general function of digestive enzymes? They breakdown large molecules into smaller molecules.

8 3. Where is the enzyme amylase produced? In the salivary glands, the pancreas and the small intestine. 4. What does amylase do? It catalyses the breakdown of starch into sugars in the mouth and small intestine. 5. Where is the enzyme protease produced? In the stomach, the pancreas and the small intestine. 6. What does protease do? It catalyses the breakdown of proteins into amino acids in the stomach and small intestine. 7. Where is the enzyme lipase produced? In the pancreas and small intestine. 8. What does lipase do? It catalyses the breakdown of lipids (fats and oils) into fatty acids and glycerol in the small intestine. 9. What conditions do the enzymes in the stomach work best in? Acidic 10. Approximately what is the ph of the acid in the stomach? ph Where is bile produced? Liver 12. What does bile do? It acts in the small intestine to neutralise the acid from the stomach. 13. Do enzymes in the small intestine prefer alkaline or acid conditions? Alkaline (this is why the bile is added to neutralise the acid, it also makes the solution slightly alkaline) 14. Name 3 processes where enzymes work inside cells. Enzymes for respiration, photosynthesis and protein synthesis work inside cells

9 B2.6_Aerobic and anaerobic respiration B2.6.1 Aerobic respiration 1. What are chemical reactions inside the body controlled by? Enzymes 2. What are the reactants of aerobic respiration? Glucose and oxygen 3. What are the products of aerobic respiration? Carbon dioxide and water (and energy) 4. Where, in the cell, do most of the reactions in aerobic respiration take place? Mitochondria 5. How is energy produced by respiration used by ALL organisms? To build larger molecules from smaller ones 6. How is energy produced by respiration used by mammals and birds? To maintain a steady body temperature in colder surroundings 7. How is energy produced by respiration used by plants? To build up sugars, nitrates and other nutrients into amino acids which are then used to make proteins 8. What are the two main ways the body responds during exercise? Increased heart rate and rate and depth of breathing increases 9. Why does the body respond to exercise in this way? To increase blood flow to muscles, so increase glucose and oxygen supply to them (increasing rate of respiration so more energy is produced) and increase the rate of removal of carbon dioxide. B2.6.2 Anaerobic respiration 1. Which substance do muscles store glucose as? Glycogen 2. What happens to the stored glucose in muscles during exercise? Converts glycogen to glucose

10 3. Why do muscles carry out anaerobic respiration? If too little oxygen is reaching them during exercise 4. How does the breakdown of glucose differ in aerobic and anaerobic respiration? Anaerobic respiration is the incomplete breakdown of glucose 5. What is the product of anaerobic respiration? Lactic acid 6. How does the amount of energy produced differ in aerobic and anaerobic respiration? Less is produced in anaerobic 7. HT How is the oxygen debt produced by anaerobic respiration repaid? Lactic acid is oxidized (using oxygen) to carbon dioxide and water 8. Why do muscles become fatigued? If they are subjected to long periods of vigorous activity 9. What does fatigued mean? Muscles stop contracting efficiently 10. What is one of the causes of muscle fatigue? The build up of lactic acid 11. What is fermentation? The anaerobic respiration in yeast it produces ethanol and carbon dioxide B2.7 Cell division and inheritance B2.7.1 Cell division 1. How are chromosomes normally arranged in body cells? In pairs 2. What is the name of the type of cell division seen in body cells? Mitosis 3. What do chromosomes contain? Genetic information 4. What first happens to the genetic material when a body cell divides? It is copied

11 5. How many times does a body cell divide? Once 6. How does the genetic information of a new cell, produced by a body cell dividing, compare with the original cell? They are identical 7. How many sets of chromosomes does a human body cell have? Two 8. How many sets of chromosomes do sex cells have? One 9. What is another name for sex cells? Gametes 10. What is the name of the type of cell division that produces gametes? Meiosis 11. HT What first happens to the genetic material when a cell divides to form gametes? Copies of the genetic material are made. 12. HT How many divisions does an original cell go through to produce sex cells? Two 13. HT How many gametes are formed after one original cell divides? Four 14. HT How many sets of chromosomes do these gametes contain? One 15. HT How does the genetic information of gametes compare to the original cell? They have half of the information 16. What happens to at fertilisation? Gametes join to form a single body cell with a new pair of chromosomes. 17. What type of cell division happens once and egg has been fertilised? Mitosis 18. Why do mature animal cells divide? To repair and replace old cells

12 19. Where do human stem cells come from? Embryos and adult bone marrow 20. What can human stem cells have the ability to do? Develop into any type of human cell 21. When do animal cells differentiate compared to plant cells? Animal cells differentiate at early stages, whereas many plant cells retain the ability to differentiate throughout life. 22. How many pairs of chromosomes are there in a human body cell? 23 pairs B2.7_Cell division and Inheritance B2.7.2 Genetic variation 1. How does sexual reproduction give rise to variation? Reproduction without the need for fertilisation (mitosis from a single cell) 2. How are inherited characteristics controlled? Some are controlled by a single gene, others are controlled by a number of genes. 3. What is an allele? A different form of a gene 4. What is a dominant allele? An allele which controls a characteristic when it is present on only one of the chromosomes in the pair 5. What is a recessive allele? An allele which controls the development of characteristics only if the dominant allele is not present. 6. Which molecule are chromosomes made from and what is its structure like? DNA 7. What is a gene? A small section of DNA 8. What does a gene contain? The genetic code for a particular sequence of amino acids which makes a specific protein. 9. What does DNA fingerprinting tell us? Each person has a unique DNA which can be used to identify individuals.

13 10. What are the female sex chromosomes? XX 11. What are the male sex chromosomes? XY 12. HT What is a monohybrid cross? A cross (joining of gametes) between organisms which looks at only one allele at a time. 13. HT What does homozygous and heterozygous mean? Homozygous means both alleles which code for a particular protein are the same (bb or BB), heterozygous means alleles are different (Bb). 14. HT What does genotype mean? A description of the alleles present. e.g. Bb 15. HT What does phenotype mean? A description of the observed characteristic e.g. brown hair. 16. What are genetic disorders? Disorders which are inherited due to mutations in genes. 17. What is polydactyly? When a person is born with extra digits (fingers and/or toes). 18. How is polydactyly inherited? It is caused by a dominant allele and can be passed on by only one parent who has the disorder. 19. What is cystic fibrosis? A disorder of cell membranes which makes patients produce more mucus (particularly in lungs) than normal. 20. How is cystic fibrosis inherited? It is a recessive disorder so both parents must be carriers of the cystic fibrosis allele. 21. What does a carrier mean? Someone who has the allele for a disorder but does not have the disorder themselves. Carriers can only be present in inherited disorders which are recessive. 22. How can you carry out screening for these disorders? You can screen embryos for the alleles of genetic disorders. 23. What is a generic pedigree? A diagram that shows who in a family have a genetic disorder, are carriers and are normal. 24. What ideas did Mendel propose and why was this discovery not recognised until after his death?

14 They did not take him seriously and knew nothing about genes. 25. Which organism did Mendel carry out most of his research on? He looked at pea plants. B2.8_Speciation B2.8.1 Old and new species 1. Where does evidence for early forms of life come from? Fossils 2. Why are scientists not certain about how life began on Earth? Because early forms of life did not leave much fossil evidence, they did not have bones and may have been disrupted by the Earth s natural movements. 3. What is a fossil? The remains of organisms from many years ago, found in rocks. 4. How are fossils formed? 1. From the hard parts of animals that do not decay easily. 2. From parts of organisms that have not decayed because one or more of the conditions needed for decay are absent e.g. oxygen. 3. What parts of the organism are replaced by other materials as they decay. 4. As preserved traces of organisms e.g. footprints, burrows and faeces. 5. What can we learn from the fossil record? How much or little organisms have changed as life developed on Earth. 6. How might extinction be caused? By changes to the environment, new predators, new diseases, new and more successful competitors, a single catastrophic event 7. HT What is speciation? When an isolated population becomes so different from the original population that a new species is produced. 8. HT Describe the process of natural selection. Variation populations of organisms have variations. Over production produce more young than will survive to adulthood. Struggle for existence competition for survival between the organisms Survival those with advantageous characteristics are more likely to survive Advantageous characteristics inherited better adapted organisms are more likely to reproduce successfully passing on the advantageous characteristics to their offspring in their genes. Gradual change over a period of time the more individuals with the advantageous characteristics in the population.

15 QWC 6 MARK QUESTIONS 1. Compare and contrast the structure of plant, animal, bacteria and yeast. Plant and animal cells have a nucleus that contains DNA. In a bacterial cell the DNA is in a giant loop called chromosomal DNA and there are also small rings of DNA called plasmids. All three types of cell contain cytoplasm and have a cell membrane. Plant and animal cells contain mitochondria which is where respiration takes place. Plant cells and bacterial cells have a cell wall, but the cell wall of bacterial cells is more flexible and not made of cellulose. Plant cells also have chloroplasts, containing chlorophyll and a vacuole containing water and cell sap. Bacteria cells are much smaller than plant and animal cells. Yeast is a single celled organism which has nucleus, cytoplasm and cell membrane like an animal cell but also has a cell wall. 2. Describe what tissues are and outline the function of a range of tissues in both plants and animals. Tissues are groups of cells with similar structure and function. Humans have muscular tissue which contracts to bring about movement, for example to churn the contents of the stomach. They also have glandular tissue which produces hormones and enzymes such as those involved in digestion. They also have epithelial tissue which covers some part of the body, for example the skin and the outside and inside of the stomach and intestines. Plants also have epithelial tissue which covers the plant. Photosynthesis takes place in the palisade mesophyll tissue. The xylem and phloem tissue transport substances around the plant. Xylem transports water and minerals and phloem transports the glucose produced in photosynthesis. 3. Describe the journey of a cheese sandwich through the digestive system, including the role of enzymes. (Hint: cheese is protein and bread is a carbohydrate) The cheese sandwich would begin to be digested in the mouth through chewing and the action of amylase which would break down the carbohydrate in the bread into glucose. This would pass down into the stomach where it would be churned by the muscular bag and the cheese would be digested by protease enzymes like pepsin into amino acids. The pancreas will produce protease, carbohydrase and lipase enzymes which will be released into the small intestine and break the food down into soluble substances: amino acids, sugars, fatty acids and glycerol. The food will move into the small intestine and these soluble substances will be absorbed into the blood. The liver will also produce bile which emulsifies fats into smaller droplets and neutralises acid from the stomach. Any undigested food will pass into the large intestine where water will be absorbed leaving a faeces which passes out of the anus. 4. Explain how plants make glucose and suggest what glucose is used for in the plant Plants make glucose in a chemical reaction called photosynthesis. Plants take in carbon dioxide from the air and water from the soil and these react together in mesophyll tissue in the leaf to form glucose. Oxygen is also released as a by-product. This process requires light energy from the sun. The glucose produced in photosynthesis may be converted into insoluble starch for storage.

16 It can also be used to produce fats and oils for storage. Plants also use glucose for respiration, to make proteins and to produce cellulose which strengthens cell walls. 5. Describe a method to investigate how light intensity affects the rate of photosynthesis. A plant, such as Elodea pondweed can be placed in a beaker with a funnel over the top. When the plant photosynthesises, bubbles of oxygen will be produced. Counting the number of bubbles produced in a minute, indicates the rate of photosynthesis. A lamp could be placed at various distances away from the plant eg. 10, 20, 30, 40, 50 and 60cm as this would change the light intensity: the closer the lamp, the higher the light intensity. The number of bubbles produced in a minute could be counted to see if light intensity changes the rate of photosynthesis. This would be repeated twice to ensure reliable readings. To make the experiment valid, the type of plant, amount of water, amount of carbon dioxide and the temperature would all need to be controlled. 6. In a commercial greenhouse, a light automatically switches on at 17:00 in winter and a heater is turned on when the temperature drops below 210C. Explain why. Commercial greenhouses are used to grow plants to sell and the farmer wants a high yield. Light intensity is a limiting factor in photosynthesis and if the light intensity is low, for example at night, then photosynthesis will happen slowly or not at all and the plant will make less glucose, making it grow more slowly. In a greenhouse, the farmer wants to maximise growth and so artificial lights are used when it is dark to ensure a maximum rate of photosynthesis. Temperature is another limiting factor as the enzymes in photosynthesis will not work when the temperature is too high or too low. When the temperature drops below 210C, the rate of photosynthesis becomes too slow so heaters are used to ensure that photosynthesis continues to take place to provide glucose for growth. 7. Explain how leaves are adapted to make them efficient sites for photosynthesis. Leaves have several layers with different features to make them adapted for photosynthesis. They have tall palisade mesophyll cells which have a large surface area and are packed with chloroplasts to absorb light energy for photosynthesis. Below this is a spongy layer with air spaces to provide a large surface area for gas exchange. On the bottom of the leaf are tiny holes called stomata. Carbon dioxide and water vapour diffuse in through the stomata for photosynthesis and the oxygen produced diffuses out. Guard cells on either side of the stomata, cause the stomata to open or close to reduce water loss when the plant is dry. 8. A property developer is planning to build on a large field but they are concerned about the wildlife. Explain how scientists could investigate the distribution of organisms in the field in and obtain valid and reproducible data. They could use a tape measure to create a transect line across the field which is selected at random. They could then place a quadrat at regular intervals along the transect and count how many organisms are inside it. Alternatively, quadrats could be placed at random in the field and the number of different types of organisms inside them counted. Then you would multiply and scale up the mean number of one type of organism per quadrat to estimate the number in the whole field.

17 To ensure that the data was valid and reproducible you would need to make sure that the location of the transect or quadrats was selected at random and a large sample size of quadrats was used. 9. Describe how different proteins are made from the genetic code and what roles proteins play in the body. Each section of DNA (called a gene) codes for a particular combination of amino acids. These amino acids join together in a specific order to make different proteins. This happens in ribosomes in the cell. Proteins are therefore made up of long chains of amino acids which play different roles in the body. They act as structural components of tissues such as muscles, they act as hormones, antibodies and catalysts. Enzymes are biological catalysts and are therefore also proteins. 10. Describe an experimental method to investigate the effect of the concentration of carbohydrase enzyme on the digestion of starch. The rate of digestion of starch can be measured with the help of iodine solution. Iodine solution turns blue/black in the presence of starch but remains brown in glucose. We can therefore measure how quickly the iodine turns brown and this will tell us how quickly starch is being broken down into sugar. We could place starch solution into 5 different test tubes and add carbohydrase enzyme of different concentrations eg. 2%, 4%, 6%, 8% and 10% and time how long it takes for the iodine to turn brown. We could need to keep the amount of starch solution, amount of carbohydrase enzyme, amount of iodine, the temperature and the ph the same to make it a fair test. I would repeat the experiment twice and calculate an average using my results. 11. Explain how 3 factors affect enzyme action. Enzyme action is affected by 3 factors: temperature, ph and substrate concentration. Enzymes work best at an optimum temperature and for most enzymes, it is around 370C. If the temperature is lower than this then the enzyme is inactive but as the temperature rises the rate of a reaction will get faster as there will be more successful collisions between reactants. Once the temperature gets higher than the optimum the enzyme will be denatured and its active site will change shape so that it no longer fits with the substrate and cannot work any longer. Enzymes also have an optimum ph and if the ph is too acidic or alkaline then the enzyme will also be denatured and it will be unable to catalyse the reaction. Increasing the concentration of substrate will increase the rate of the reaction as there will be more successful collisions between reactants. However, once all of the active sites on the enzymes are full, the enzyme cannot work any faster on the substrate so increasing the concentration further has no effect. 12. Suggest several uses of enzymes in industry and evaluate their use. Enzymes have several uses in industry as they are used to catalyse biological reactions. Proteases are used to pre-digest the protein in some baby foods to make it easier for the babies to digest. Carbohydrases such as amylase are used to convert starch into sugar syrup when it is made. Isomerase enzymes are used to convert glucose syrup into fructose syrup which is much sweeter. This means that it can be used in much smaller amounts for slimming foods. The advantages of using enzymes in industry are that it reduces the costs because reactions can be carried out at lower temperatures and pressures without expensive energy demanding equipment.

18 However the enzymes themselves can be very expensive to produce and they are denatured if the temperature is too high or the ph is not right so these conditions need to be carefully monitored. 13. Eero Mantyranta is an Olympic skier who inherited a mutation causing him to have more red blood cells than normal. Suggest why this gave him an advantage over others. Red blood cells carry oxygen so his blood will be able to carry more oxygen than normal. Oxygen is needed for respiration so this means that he will be able to respire at a faster rate. This will produce more energy for muscle contractions which will improve his performance. It also means that he will be able to respire aerobically for longer than other athletes before anaerobic respiration takes over. This will mean that he is less likely to suffer from cramp and muscle fatigue, improving his performance. Aerobic respiration also produces more energy than anaerobic respiration which will provide more energy for movement. 14. Explain why it takes several minutes for athletes heart rate and breathing rate to return to normal after vigorous exercise. During exercise, an athlete s heart rate and breathing rate increase because more oxygen and glucose is needed for aerobic respiration to provide energy for muscle contraction. Therefore, more oxygen needs to be breathed in and the heart needs to pump more blood containing oxygen and glucose to muscle cells. Additionally, more carbon dioxide and water are also produced which need to be pumped back to the lungs in the blood and carbon dioxide needs to be breathed out. If exercise is vigorous, the athlete may not be able to breathe in enough oxygen for aerobic respiration so anaerobic respiration may take over. This produces lactic acid, which pools in the muscles and causes cramp. In order to breakdown the lactic acid, oxygen is needed at the muscle cells: lactic acid + oxygen -> carbon dioxide + water. The amount of oxygen that is needed to break this down this lactic acid is called the oxygen debt and heart rate and breathing rate need to remain high for a period after exercise to provide muscle cells with the extra oxygen needed and to take away the carbon dioxide and water. 15. Describe how oxygen and glucose are absorbed and transported to cells. Oxygen is breathed into the lungs, into the alveoli. It then diffuses from a high concentration to a low concentration across the walls of the alveoli into the capillaries and into the blood. It is carried to capillaries all over the body where it diffuses across the capillary wall into cells where it is needed for respiration. Glucose comes from food and more complex carbohydrates such as starch are broken down into glucose by carbohydrase enzymes. This starts in the mouth and continues as the food passes through the digestive system. Glucose is absorbed into the blood in the small intestine where it diffuses across the walls of the villi, which each have their own capillary network, into the blood and it is transported in blood vessels to cells for respiration. 16. Explain why Mendel proposed the idea of separately inherited factors and why the important of this discovery was not realised until after his death. Gregor Mendel carried out several experiments with different plants and noted how characteristics are passed on from one generation to the next. For example, he looked at the inheritance of height in pea plants. He firstly crossed a tall pea plant with a dwarf pea plant and found that all of the offspring were tall.

19 This lead to the idea of dominant alleles, in this case the gene for tall height. He secondly crossed the new offspring together who had one tall allele and one dwarf allele and found that the offspring were both tall and dwarf in the ration 3:1. This lead to the idea of recessive alleles as the dwarf plant must have two dwarf alleles. The importance of this discovery was not realised at the time because genes and DNA had not yet been discovered and people knew very little about genetics. 17. Suggest several uses of stem cells in medicine and evaluate their use. Stem cells are very useful cells that are able to divide many times and differentiate to become any other kind of human cell. They are found either in adult bone marrow or from human embryos. They are extremely useful in treating diseases in humans. They can be used to grow new nerve cells to treat paralysis, to grow new blood cells to treat leukaemia and to grow new tissues for transplant. However some people disagree with stem cell treatment as stem cells are taken from embryos left over from fertility treatment and when the stem cells are taken the embryo is killed. Some people have strong ethical and religious objections to this. 18. Compare and contrast the two different types of cell division Mitosis is a type of cell division that is needed for growth and repair. In mitosis the DNA in the parent cell is copied and the cells then divides into two new daughter cells. These cells are genetically identical to the original parent cell and each one contains 46 chromosomes. This is a form of asexual reproduction as all of the cells are genetically identical. Meiosis is also a type of cell division but this is needed for the production of gametes (egg and sperm cells). In meiosis, the DNA in the parent cell is copied and the cell divides but it then divides again, forming four new daughter cells. These cells are all genetically different and contains only 23 chromosomes. These gametes can then combine in sexual reproduction which creates variation in the offspring. 19. Explain, with the use of a genetic diagrams why if a child has only one parent with cystic fibrosis they will not inherit the disorder but if a child has one parent with polydactyly they have a 50% chance of having the disorder. Cystic fibrosis is caused by a recessive allele. If only one parent has the disorder then the offspring will have a 50% chance of not having the allele at all and a 50% chance of being a carrier. The child would need two cystic fibrosis alleles in order to inherit the disorder. A is the polydactyl allele

20 However, polydactyly is caused by a dominant allele so the child only needs to inherit one polydactyly allele to suffer from the disorder. Therefore, if one parent has the disorder then the child has a 50% chance of inheriting the allele and having polydactyly. 20. Explain what the fossil record can tell us and suggest why we cannot be certain about how life began on Earth. There are several pieces of evidence for evolution. The main piece is the fossil record which shows the history of life on Earth through fossils from different time periods. Fossils show how organisms have changed and adapted over long periods of time and Darwin argues that this has happened through natural selection. There are however, gaps in the fossil record as soft tissues decay and do not form fossils and many fossils are buried so deeply that they may not have been found. One, particular gap is the lack of any intermediate fossils between fish and amphibians to show how they evolved. Another piece of evidence for evolution is that most vertebrates and their fossil ancestors have pentadactyl (five fingered) limb structure. This suggests that these vertebrates evolved from a common ancestor and have evolved over time to adapt to their differing environments. 21. Explain how two completely new species can arise from a single population. Two groups from a single population can become separated geographically and isolated from one another. Each population has a wide range of alleles that control their characteristics. If the two environments are different then the alleles that result in organisms being better adapted for their environment are selected. The organisms with these alleles are more likely to survive in the environment. They then pass on their genes to the next generation. Gradually over time, these alleles become more common in the population. The two populations become so different that they can no longer breed to produce fertile offspring. This is called speciation.

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