Population can increase rapidly Species may only be suited to one habitat (Unresistant to changes)

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1 B8: Plant and Human Reproduction & B9: Inheritance B8.1 Asexual and sexual reproduction Asexual reproduction: the process resulting in the production of genetically identical offspring from one parent. (Only carries traits from the one parent) Advantages Disadvantages Population can increase rapidly Species may only be suited to one habitat (Unresistant to changes) Can exploit a suitable habitat quickly (well adapted to particular environment) Disease contracted may affect all the individuals in a population Genetically identical No genetic diversity/variation in a population Fast, less energy is wasted Crowding (competition) Can reproduce on its own Sexual reproduction: the process involving the fusion of haploid nuclei to form a diploid zygote and the production of genetically dissimilar offspring. (Carry traits from both parents) Advantages Opportunity to introduce genetic diversity/variation into a population Species can adapt to new environments, surviving better (natural selection) Disadvantages Time and energy needed to find a mate Reproduction is not possible for an isolated individual Disease less likely to affect all individuals in the population Plants can disperse seeds, colonise new areas and increase its population 8.2 Sexual reproduction in plants

2 (courtesy of enchanted learning.com) Carpel (female parts of flower) > made of stigma, style, ovary, ovules Stamen (male parts of lower) > made of anther and filament Structure Function Sepal Protects unopened flower Petal May be brightly coloured to attract insects for pollination Stamen Male part of the flower, made of an anther attached to a filament Anther Produces male sex cells (pollen) Stigma Collects pollen grains (top female part of the flower) Ovary Produces female sex cells (in the ovules) Petiole (Stalk) Supports the plant, conducts H nutrients from roots + food in form of glucose from leaves to other plant parts Style Connects the stigma and the ovary Carpel Female part of the flower, including stigma, style, ovary, ovules Filament Joints the anther to the rest of the flower

Stamens Both the stamens and stigmas hand outside the flower Stigmas Pollination: the transfer of

3 (Pollen grains under a light microscope) Shows cross section of a wind pollinated flower (courtesy of bbc bitesize) Structure Feature Small petals Found in grasses that have wind pollinated flowers Stamens Both the stamens and stigmas hand outside the flower Stigmas Pollination: the transfer of pollen grains from the anther (male part) to the stigma (female part). Agents of pollination: Insects Wind

Humans (courtesy of bbc bitesize) Factors of germination: Water Oxygen, O 2 Suitable temperature Factor Explanation Water Absorbed through micropyle, needed to activate enzymes.

4 Humans (courtesy of bbc bitesize) Factors of germination: Water Oxygen, O 2 Suitable temperature Factor Explanation Water Absorbed through micropyle, needed to activate enzymes. (enzymes convert insoluble food stores into soluble foods needed for growth and energy production ) Oxygen Needed for respiration (release energy for growth and chemical changes to transport food reserves) Temp & ph For enzymes to work, bc they work best in optimum temp Light Some seeds need a period of exposure to light before germinating

Seed structure Part of the seed Structure Function Testa Tough protective covering Protects the seed, also from fungi, bacteria and insects Retains the water Cotyledons Food store Store of food

5 Seed structure Part of the seed Structure Function Testa Tough protective covering Protects the seed, also from fungi, bacteria and insects Retains the water Cotyledons Food store Store of food (starch) for the young plant to use until large enough to photosynthesise and makes its own food Radicle Part of embryo Root which grows and develops into the root system of the plant Plumule Part of embryo A shoot which develops into the adult plant Micropyle Tiny hole in testa Admits water into the embryo before active germination Hilum A scar near the micropyle Scar left by stalk which attaches the ovule to the ovary wall Seed and fruit dispersal Methods: Method Example Explanation Wind Dandelion, sycamore fruits Seeds are light and have extensions, acting as parachutes/wings to catch the wind Animal Tomato, plum, Coloured, succulent fruits that contain seeds

(internal) raspberry, grape with indigestible coats, allowing them to pass through animal undamaged Animal (external) Explosive/self propelled Goose grass, burdock Pea pod Fruits have hooks that

6 (internal) raspberry, grape with indigestible coats, allowing them to pass through animal undamaged Animal (external) Explosive/self propelled Goose grass, burdock Pea pod Fruits have hooks that attach the fruit to the fur of passing animals Pod bursts open when ripe, projecting the seeds away from the plant Seed and fruit dispersal by wind and animals allows plants to colonise new areas and decrease competition 8.3 Sexual reproduction in humans (Shows male reproductive system) Structure Function Penis To introduce the sperm cells into the vagina of the female during intercourse Sperm ducts Conveys sperm to the urethra Testes To produce sperm (male gametes) from their coiled tubes and make the male sex hormone (testosterone) at puberty Urethra To lead the sperms to the outside through the penis Scrotum A sac in which a testis is located. Suspended outside the main body cavity for faster/more rapid sperm production because of cooler conditions Prostate gland To produce a fluid to nourish the sperm cells and help them swim vigorously Fluid + sperm cells = semen

Structure Function Uterus For the implantation and development of the embryo Vagina To lead mature ova to the uterus, its also a region where fertilisation of ova by sperm takes place Oviduct

7 Structure Function Uterus For the implantation and development of the embryo Vagina To lead mature ova to the uterus, its also a region where fertilisation of ova by sperm takes place Oviduct Connects the uterus to the vagina Ovary To produce eggs/ova at puberty and female sex hormones Cervix To receive sperm cells during intercourse, also birth canal for the baby Comparing male and female gametes Male Female Size Very small Relatively large Numbers Millions Approx one produced every month Mobility Has a tail for swimming to the ovum Stationary Egg/Ovum (Female Gamete)

(courtesy of bbc bitesize) (Also includes layer of jelly outside the cell membrane) Structure Function Haploid Nucleus Contains half the number of chromosomes of a normal

Sperm cell (Male gamete) Structure Function Tail For swimming to the ovum (mobility) Energy is required energy is produced in the mitochondria Mitochondria Where

8 (courtesy of bbc bitesize) (Also includes layer of jelly outside the cell membrane) Structure Function Haploid Nucleus Contains half the number of chromosomes of a normal cell nucleus Cytoplasm Contains nutrients and mitochondria needed for mitosis (cell division) after fertilisation Cell membrane Only allows one sperm to fertilise the egg Sperm cell (Male gamete) Structure Function Tail For swimming to the ovum (mobility) Energy is required energy is produced in the mitochondria Mitochondria Where respiration occurs to release energy needed to travel through cervix, uterus and fallopian tube towards the egg Acrosome (enzyme) Allows sperm to break through the cell membrane of the egg

9 Fertilisation: fusing together of the nuclei of male gamete (sperm) and the female gamete (egg). Menstrual cycle: A monthly cycle in which a woman s uterus prepares for a fertilised egg to settle and grow into a baby Lining of the uterus prepares for pregnancy. If pregnancy does not occur, the lining breaks down and menstruation occurs Cycle lasts about 28 days, period (made of blood and uterus lining, passed out of body through vagina) lasts for 3 7 days After menstruation/period, uterus lining builds up again/thickens in preparation for a fertilised egg At approximately day 14 of menstrual cycle, ovulation occurs (an egg is released from a follicle in the ovaries) 2 ways: If egg is fertilised and embeds itself in thickened lining of uterus, woman becomes pregnant. If not, lining breaks down and menstruation occurs. Cycle repeats itself. (courtesy of bbc bitesize) Development of zygote

10 After fertilisation takes place in the oviduct, fertilised ovum ( zygote ) starts to divide ( mitosis which is cell division occurs). Now, the formed ball of cells move down the oviduct, taking several days to reach the uterus. It is now an embryo. Now in the uterus, implantation (when the embryo sinks into the soft lining of the uterus) occurs. Embryo gets oxygen and nutrients from blood vessels in the uterus lining, allowing it to grow and develop. Amnion : A membrane that encloses the amniotic fluid (ruptures before birth) Amniotic sac : Produces amniotic fluid which surrounds and protects the developing embryo. Amniotic fluid : Protects fetus from drying out, temperature fluctuations, unequal pressures acting on the fetus, physical damage by acting as a shock absorber. Placenta : Develops from the embryo, placenta anchors the embryo in the uterus, allowing (connected by umbilical cord to embryo) Exchange of nutrients and oxygen from mother to embryo (Passes by diffusion fetus blood and mother s blood does not mix) Waste materials and CO 2 from embryo to mother Umbilical Cord: Cord that connects foetus to the mother. Also contains blood vessels. Breast feeding VS bottle feeding using formula milk Advantages Passing on of antibodies from the mother Easy digestion, natural Increased level of nutrients Disadvantages Insufficient supply, time consuming Privacy (Convenience, location), painful Varies by mother s diet (eg. alcohol) Virus can be passed from mother to child Methods of transmission of HIV Sex Unsterilized needles Contaminated blood transfusion. Ways to prevent spreading of HIV/AIDS Use condoms Ensure you use sterilized needles

11 How HIV affects immune system of a person with HIV/AIDS Weakens the immune system by attacking and targeting the body s vital cells in the immune system such as the dendritic cell, T cells and macrophages. B9: Inheritance 9.1 Chromosomes and Genes I nheritance: the transmission of genetic information from generation to generation Chromosome: a thread of DNA, made up of a string of genes Genes: a length of DNA that is the unit of heredity and codes for a specific protein. Can be copied and passed on to the next generation. Allele: Any of two or more alternative forms of a gene Haploid nucleus: a nucleus containing a single set of unpaired chromosomes (eg. sperm or egg) Diploid nucleus: a nucleus containing two sets of chromosomes (eg. in body cells) Inheritance of sex in humans Females: XX Males: XY 9.2 Cell Division Mitosis: nuclear division giving rise to genetically identical cells in which the chromosome number is maintained by the exact duplication of chromosomes. Role of mitosis in growth, repair of damaged tissues, replacement of worn out cells and asexual reproduction Produce more cells during growth, repair of tissues and replacement of worn out cells Key process in asexual reproduction Result of meiosis: Gametes Genetic variation (cells produced are not all genetically identical)

o Production of genetically identical offspring from one parent o E.g. - Bacteria Reproduce by binary fission a cell to divide into 2

Reproduction (IGCSE Biology Syllabus 2016-2018) Asexual Reproduction o Production of genetically identical offspring from one parent o E.g. - Bacteria Reproduce by binary fission a cell to divide into