Chapter 16 Reproduction IGCSE Biology Gardens 2024 PDF

by dr. MOATAZ BEDEWEY 00201110983031 CELL :01110983031 00201110983031 [email protected]  1. 1 Describe asexual reproduction as a process resulting in the production of genetically identical offspring from one parent 2 Identify...

by dr. MOATAZ BEDEWEY 00201110983031 CELL :01110983031 00201110983031 [email protected]  1. 1 Describe asexual reproduction as a process resulting in the production of genetically identical offspring from one parent 2 Identify examples of asexual reproduction in diagrams, images and information provided Supplement 3 Discuss the advantages and disadvantages of asexual reproduction: (a) to a population of a species in the wild (b) to crop production 4 Identify in diagrams and images and draw the following parts of an insect-pollinated flower: CELL :01110983031 00201110983031 [email protected]  Reproduction 1. Reproduction the processes that make more of the same kind of organism. Types of reproduction 1. Sexual reproduction 2. Asexual reproduction 1.ASEXUAL REPRODUCTION Definition: A type of producing new genetically identical offspring from one parent only without producing gametes Gametes: Cells produced from a male and a female to fuse together producing one cell called zygote that divide producing a new organism Types of Gametes in animals Sperm In males Ovum in females. CELL :01110983031 00201110983031 [email protected]  Types of asexual reproduction 1. Binary fission 2. By spores 3. by budding 4. by tubers 1.binary fission Bacteria reproduce by cell division (fission). Any bacterial cell can divide into two and each daughter cell becomes an independent bacterium. In some cases, this cell division can take place every 20 minutes so that, in a very short time, a large colony of bacteria can be produced. CELL :01110983031 00201110983031 [email protected]  2. by spores in fungi 1. Fungus that reproduces by spores contains two parts that are aerial hyphae and rhizoid. 2. Aerial hyphae contain 2 parts that are sporangium and sporangiophore. 3. Sporangium contains spores. How a fungus spreads to a new source of food 1. Fungus produces spores in sporangia and spore case which bursts releasing spores that spread by wind. 2. when spores fall on food in suitable conditions such as temperature and humidity, they germinate leading to formation of new fungi. CELL :01110983031 00201110983031 [email protected]  2.Budding in yeast Asexual reproduction in potatoes Example (Tuber formation in potatoes) What is meant by tuber Short underground stem or root usually much enlarged, and has a storage function. Steps of tuber formation : 1.In the potato tubers there are grooves called eyes (Each eye contains a bud with scale leaf) CELL :01110983031 00201110983031 [email protected] 2. In favorable conditions buds grow using the stored food in the tuber producing new shoot and root 3. Roots grow down and the shoot forms leaves. Attention Explain Steps of tuber formation 1. Underground side stems grow out from the base of the main stem. 2. Food is stored in the underground stems forming new tubers. 3. The leaves, stems and old tuber die, but the new tubers remain dormant until the conditions become favorable. CELL :01110983031 00201110983031 [email protected]  Advantages and disadvantages of asexual 2. Sexual reproduction A process involving the fusion of haploid nuclei to form a diploid zygote and the production of genetically different offspring. CELL :01110983031 00201110983031 [email protected]  advantages and disadvantages of asexual reproduction CELL :01110983031 00201110983031 [email protected]  REPRODUCTION IN PLANTS 1.Identify in diagrams and images and draw Describe self-pollination as the The following parts of an insect-pollinated transfer of pollen flower: sepals, petals, stamens, filaments, anthers, grains from the anther of a flower carpels, style, stigma, ovary and ovules to the stigma 2 State the functions of the structures listed in of the same flower or a different 16.3.1 flower on the 3 Identify in diagrams and images and describe The anthers and stigmas of a wind-pollinated same plant Flower. 10 Describe cross-pollination as the 4 Distinguish between the pollen grains of transfer of insect-pollinated and wind-pollinated flowers pollen grains from the anther of a 5 Describe pollination as the transfer of pollen grains from an anther to a stigm flower to the stigma of a flower on a different plant of the same species 11 Discuss the potential effects of self-pollination and cross-pollination on a population, in terms of variation, capacity to respond to changes in the environment and reliance on pollinators CELL :01110983031 00201110983031 [email protected]  Sexual reproduction in flowers 1. Receptacles Enlarged, extended part of stem Carriers the flower 2. Sepals: small and green Protect the flower while it is closed 3. Petals: large, colored and sometimes scented have smell  Attract insects for pollination some have guide lines to the nectary gland  Used for landing of insects  Surround and protect the reproductive organs of the flower. CELL :01110983031 00201110983031 [email protected]  Stamen: Each consists of an anther and a filament Anther: contain pollen sac to produce pollen grains that contain male gametes in flowering plants filaments: carry the anther and hold to be exposed to agents of pollination  Carpels: Are the female organs Each consists of stigma style and ovary. Stigma: receives the pollen produce nutritive materials pollen to germinate. Style: holds the stigma to be exposed agents of pollination. Ovary: produces ovules that that contains female gametes in Flowering plants. Nectary gland: Makes sugary solution called nectar me to be used by insects as food. Explain the Stages of reproduction in flowering plants: 1.Pollination: is the transfer of pollen grains from anther to a stigma. 2. Fertilization It is the fusion of the male gamete and the female gamete producing a cell called zygote. CELL :01110983031 00201110983031 [email protected]  Types of pollination 1.Self-pollination: the transfer of pollen from an anther to the stigma of the same flower or another flower on the same plant. 2. Cross pollination: It is the transfer of pollen from an anther of a flower to stigma of another flower on another plant of the same species. CELL :01110983031 00201110983031 [email protected] Characteristics of self- and cross-pollinated flowers CELL :01110983031 00201110983031 [email protected] Explain Implications of self-pollination. 1.Produces less variation than cross pollination, therefore, plants with good strains are more likely to produce offspring of good strains 2. It is a disadvantage if there is a change in the environment, as there is no enough variation, therefore most of such strains maybe unable to live in the new conditions, or if a mutation developed in pests, such plants may be unable to resist it. Explain Implications of cross pollination 1.Produces more variation which is necessary for natural selection and evolution. 2. disadvantage of cross pollination is that good strains are not necessary to produce good strains. Agents or means of pollination 1-Wind 2-Animals 3-Humans 4-Insects CELL :01110983031 00201110983031 [email protected]  insect pollinated flowers features 1. Usually, large 2. Appear in warm times 3. Scented to attract insects 4. Have nectary glands to secrete 5. reproductive organs are enclosed within the flower, so that the insect has to brush it to reach the nectar gland. features of pollen grains 1.Sticky to cling to insects. 2. Small in number. 3. Larger than those carried by wind.  wind pollinated flowers 1. Usually, small. 2. Appear in cold weather. 3. Nectar Not scented. 4. Reproductive organs are projected outside the flower. CELL :01110983031 00201110983031 [email protected]  Pollen grains features 1.Small, light and dry to be carried by wind. 2.Larger in number as most of them are lost..3.Stigma is feathery to trap pollen grains from air Fertilization 1. when a pollen grain run from the stigma , the stigma produces a sticky nutritive fluid. 2. The pollen grain absorbs this fluid producing a pollen tube, and the nucleus of the pollen grain which is the male gamete) passes through the tube 3. The pollen tube grows towards the ovule till it reaches the micropyle.(the position where the male nucleus passes to the ovule) 4. the nucleus of the pollen grain fuses with the nucleus (which is the female.gamete) producing a zygote CELL :01110983031 00201110983031 [email protected]  Changes After fertilization Explain What happens after fertilization: 1-Sepals, petals, stamens, stigma and style dry up and fall. 2.The ovule develops into seed. 3.The integument becomes the Testa of the seed. 4.The ovary enlarges and becomes the fruit. 5.The wall the ovary becomes the pericarp. Functions of the fruit to the plant: 1. Protects the seed. 2. Helps dispersal. 3. Stores food. CELL :01110983031 00201110983031 [email protected]  The structure of a non-endospermic seed 1. Testa: non –permeable : becomes soft and rupture during germination 2. Cotyledons : store food 3. Radical : grow producing young root 4. Plumule: grows producing young shoot Micropyle: it is the pathway where the water enters into the seed. CELL :01110983031 00201110983031 [email protected] Dispersal is the spreading out of seeds and fruits. CELL :01110983031 00201110983031 [email protected]  Types of Dispersal 1.Wind Dispersal Examples: Wind Dispersal Animal Dispersal Sycamore Burdock It has wing-like structure Why ? to allow it to be carried by wind for a long distance by increasing its surface area 2. Animal Dispersal Examples: Dandeloin. Why this plant has hooks? to cling to the fur of animals or feathers of birds to be carried away from one place to another Example : Indigestible seeds and fruits CELL :01110983031 00201110983031 [email protected] Tomatoes, apple and strawberry have indigestible seeds or fruits therefore when an animal eats them, their indigestible parts are evacuated with stool to germinate. Germination The beginning of growth of an embryo or a spore, this growth takes place by using the stored food in the spore or the seed. Stages of Germination 1. The seed takes up water through the micropyle. 2. The cotyledons swell causing the Testa to burst. 3. The enzymes in the seed become active by the effect of water. 4. Enzymes are used to digest the stored food in the seed. 5. The digested food diffuses through the embryo and used in growth. 6. Radicle emerges from the Testa. 7. Testa falls off. 8. Plumule opens out and grows into shoot. CELL :01110983031 00201110983031 [email protected]  1.Water 1. Activates the enzymes in the seeds. 2. Transports salts from the soil to the shoot. 3. Expand the vacuoles of the newly formed cells causing the root and shoot to grow. 4. Transport sugars from the cotyledons to the growing regions. 2. Oxygen Used in aerobic respiration to provide the embryo with the energy required for different metabolic reactions. 3. Suitable Temperature The best temperature is about 35 –40°C as is make the enzymes in seeds active. CELL :01110983031 00201110983031 [email protected]  1. At the beginning: 1. The dry mass decreases as the embryo breaks down amounts of the stored food to release the energy required for metabolic activities. 2. The fresh mass increases due to the absorption of water. 2. After several days: The dry mass begins to increase because this period green leaves may be formed and used for making food by photosynthesis. CELL :01110983031 00201110983031 [email protected]  REPRODUCTION IN HUMAN Humans are characterized by: 1. Internal Fertilization: means that gametes fuse inside the body of the female. 2. Internal Development: means that the embryo grows inside the body of the female. Gonads: Are the organs responsible for producing gametes. In Humans: The male gonads are the testes. The female gonads are the ovaries. CELL :01110983031 00201110983031 [email protected]  The Female Reproductive System The Female Reproductive System Definition : A type of producing new genetically identical offspring from one parent only without producing gametes. Gametes : Cells produced from a male and a female to fuse together producing one cell called zygote that divide producing a new organism Gametes in animals Sperm In males Ovum in females. CELL :01110983031 00201110983031 [email protected]  Properties and Functions of the different parts Ovaries Are two, right one and left one. Function: a. Production of Ova (singular: ovum) b. Production of the female hormones (which are known as estrogen) c. Each ovary produces an ovum per 2 months (56 days) (Therefore there is only one ovum produced every 28days by one of the two ovaries.) 2. Oviduct (Fallopian Tubes) Its front part is a funnel-shaped structure to receive ova. (this part is called funnel of the oviduct) Funnel of the oviduct and the oviduct contains cilia to push the ova into the uterus It is the site of fertilization (because of ovum dies before leaving it) CELL :01110983031 00201110983031 [email protected]  3. Uterus or Womb A muscular organ It is the site where the embryo is developed if the ovum is fertilized. it consists of a muscular wall and a lining -The lining is soft, spongy with many blood vessels to supply the embryo with food and oxygen. In the lining implantation of the embryo takes place. (Implantation means that the embryo fixed itself to the lining of uterus) If there is no fertilization the lining is broken down releasing blood, this is called menstruation. Every month new lining is formed, except during pregnancy the lining is not broken down and remain to support the embryo. During birth it contracts to push the fetus out. CELL :01110983031 00201110983031 [email protected] MALE REPRODUCTIVE SYSTEM: Properties and functions of the different structures Structure Properties and functions 1-Testes a Production of sperm b. Production of the male sex hormone which is known as testosterone 2-Scrotum o A ac of skin scrotal sac Used to hold the testes outside the body at a lower temperature CELL :01110983031 00201110983031 [email protected]  because increase in temperature affects production of sperm. 3-Epididymis A coiled tube Its functions - Stores sperms b-Contracts to help in ejaculation of sperms 4- Sperm duct Conducts sperm from the epididymis to the urethra Contracts by a process like peristalsis to help in ejaculation 5-Urethra 1. A common passage for both urine and semen 2. semen is the sperm plus the fluid produced by prostate gland and seminal vesicles) 3. Has a muscular wall to contract to help in ejaculation 4. Urination cannot take place during ejaculation because the sphincter muscle of the bladder contracts during ejaculation 6-Seminal -Secrete fluid known as seminal fluid to mix with sperm this fluid vesicles and consists of Prostate gland CELL :01110983031 00201110983031 [email protected]  - Mucus and nutrients produced by prostate gland) to facilitate copulation and swimming of sperm -Sugars fructose) to provide energy for sperm Alkaline material to neutralize the acidity of the urethra and vagina (urethra is acidic due to the remains of acidic urine ) 7-Penis It is the organ of copulation Contains erectile tissue which has blood cavities, when penis stimulated blood fill the cavities making the penis long and see enough for copulation this is known as erection Covered with a piece of skin called foreskin which removed the process of circumcision CELL :01110983031 00201110983031 [email protected]  1. Sperm adaptive features 1. contains nucleus carries the inherited Information. 2. Can produce enzymes from an organelle in the Head known as acrosome to penetrate wall of the the ovum. 3. Neck Contains mitochondria to produce the energy required for its movement. 4. Tail (flagellum) Used for its movement 2.Ovum: Adaptive features 1. Contains stored food to be used in its growth and division 2. Surrounded by jelly coat which becomes hard after fertilization to prevent any other sperm to enter. CELL :01110983031 00201110983031 [email protected]  Male gamete (sperm) Female gamete (ovum) Size smaller Larger Number larger smaller Structure Has flagella and acrosome Has jelly coat. Has no jelly coat mobility motile Not motile Fertilization 1. The semen is deposited at the top of vagina below the cervix. 2. Sperms swim using their tails through the cervix and the film of moisture lining the uterus. 3. Sperms are attracted towards the ovum due to the chemicals it produces. 4. Many sperms reach the egg , each sperm produces enzyme from its head to digest a way into the egg. 5. The sperm leaves its tail outside, then the nucleus of the sperm and that of the ovum fuse together forming a zygote. 6. Once one sperm has succeeded in penetrating the egg, a fertilization membrane is formed quickly to prevent any more sperms to enter the ovum. CELL :01110983031 00201110983031 [email protected]  IMPORTANT TERMS Zygote A cell formed due to the fusion of a male gamete and a female gamete. Embryo A ball of cells formed due to the division of the zygote by Mitosis. Fetus A mammalian embryo in fairly advanced stage of development. Ovulation Means the release of an ovum into the oviduct. CELL :01110983031 00201110983031 [email protected]  No fertilization Menstruation takes place Menstruation:  It is the breakdown of the lining of uterus in case if there is no fertilization.  It takes place due to a drop in the level of a hormone called progesterone. (Function of progesterone is to maintain the lining of Uterus) Stages of the menstrual cycle 1. The pituitary gland secretes the hormone (FSH) Follicle stimulating hormone which stimulates an ovum to develop into a larger structure called Graafian follicle. 2. Graafian follicle secretes the hormone estrogen which: A. Inhibits the production of FSH to avoid development of other ova during this period. B. Stimulates building up a uterine lining. 3. The pituitary gland produces a hormone called (LH) Luteinizing hormone to the Graafian follicle to pop out the EGG CELL into the oviduct and to develop the remaining of the follicle into a structure called corpus luteum or yellow body. CELL :01110983031 00201110983031 [email protected] 4. The yellow body produces hormone known as progesterone which causes the lining of the uterus to become thicker and to maintain it. 5. About two weeks after ovulation, the yellow body withers away, therefore the level of progesterone in the blood drops, as a result the lining breaks down and menstruation occurs. CELL :01110983031 00201110983031 [email protected]  OVARY PITUITARY GLANDS a follicle develops 1.secretes LH, FSH secretes oestrogen 2.stimulates follicle to secrete oestrogen in the blood..estrogen lining of the uterus grows thick, spongy. When the follicle is fully developed, LH and FSH increased follicles rupture and release fully developed ovarian cells (ovulation) empty follicle stops secreting FSH AND LH DECRESED oestrogen. becomes a corpus luteum. secretes progesterone. uterus lining thick, spongy, well supplied with blood in case an egg is fertiliser IF THE EGG IS FERTILIZED IF THE EGG IS NOT FERTILIZED corpus luteum does not degenerate so corpus luteum gradually disappears quickly. no more progesterone secreted uterus secretes progesterone until the lining breaks down. embryo sinks into uterus wall and a placenta develops. Placenta secretes progesterone Menstruation through pregnancy. CELL :01110983031 00201110983031 [email protected] it maintains the uterus lining so that a new follicle develops. the menstruation does not happen during pregnancy. if there is fertilization 1. Formation of embryo due to the successive division of the zygote by a method of division called mitosis. 2. The menstrual cycle stops, until after the baby has been born, this is because production of progesterone continues. to maintain the lining of uterus. 3. Implantation takes place: Implantation means the process by which the embryo attaches to the lining of uterus. 4.Formation of amnion and placenta. 1. Amnion (Amniotic sac) 1. Secretes amniotic fluid which Acts as shock absorber. 2. Protects the embryo against adhesion of organs. 3. Facilitates the movement of the fetus. 4. Provides a suitable temperature for the fetus. CELL :01110983031 00201110983031 [email protected] 5. During pregnancy it sterilized the pathway of the fetus. CELL :01110983031 00201110983031 [email protected]  2. Placenta  Formation of placenta.  Some of the cells of the embryo grow into projections called villi that fix into the uterus.  The uterus also grows projections.  The maternal (mother’s) villi, and the fetal villi grow closely together forming the placenta.  The blood in placenta includes:  Maternal blood from the uterine artery  Fetal blood from the umbilical artery and the umbilical vein in the umbilical cord. CELL :01110983031 00201110983031 [email protected]  Importance of Placenta 1. Exchange of Gases: a. Oxygen from the mother’s blood diffuses into the fetal blood b. CO2 from the fetal blood diffuses into the mother’s blood 2. Nutrition: Food materials such as glucose and amino acids diffuse or taken by active uptake into the fetal blood. 3. Excretion: Waste products such as urea diffuse from the fetal blood to mother’s blood. 4. Secretion of hormones: Secretes estrogen and progesterone to: a. Keep the uterine lining to support the embryo b. Stimulate the growth of milk producing tissues in the woman’s breast c. Prevent any more ova to be released during pregnancy 5. Makes fetal blood and maternal blood never mix in placenta therefore: CELL :01110983031 00201110983031 [email protected]  a. It protects the fetus against high blood pressure b. It protects the fetus against bacteria (If found in mother’s blood), but viruses like HIV can pass through placenta because they are very small. c. It protects the fetus and mother against blood agglutination if mother’s blood group is different. C. Umbilical Cord 1. It connects placenta and fetus Umbilical artery carries CO2 and other waste products to the placenta 2. Umbilical vein carries O2 and food materials from placenta to fetus CELL :01110983031 00201110983031 [email protected]  Sexually Transmitted Diseases (STD or Venereal Disease) Diseases which are transmitted via body fluids through sexual contact from an.infected person to a healthy one during sex intercourse AIDS (Acquired immune deficiency syndrome) Diseases Caused by a virus known as Human Immune Deficiency or HIV This virus. a. Lives in blood or bloody fluids. b. Lives in the lymphocytes damaging T-Lymphocytes decreasing immunity..c. It may live many years without any symptoms. Methods of Transmission 1. Intercourse with infected person. 2. Blood transfusion form an infected person. 3. Organ transplant form an infected person. 4. Sharing needles with infected people. Explain How to avoid it 1.Avoid intercourse with many partners. 2.Use a condom. 3.Never inject drugs..4Never share razor or tooth brush. CELL :01110983031 00201110983031 [email protected]  How HIV affects the immune system It infects and destroys lymphocytes decreasing efficiency of immune system therefore the body becomes liable to infection by other pathogens. FERTILITY DRUGS Are drug used to stimulate the development and production of ova by ovaries. They increase LH and FSH conc. In blood. Social Aspects of fertility drugs 2. Multiple pregnancies may lead to many problems such as: a. Babies may be very weak, and cannot live this causes emotional problems. b. If the babies may be defective (deformed) and this has its social and emotional problems. c. To get rid from some fertilized ova from the uterus to reduce the number of babies has its religious problems CELL :01110983031 00201110983031 [email protected]  ARTIFICIAL INSEMINATION (Vitro or glass fertilization) Fertilization outside the body of the female (or a way of fertilization different from the normal way) Social Aspects of Artificial Insemination In case of using sperms from a donor, the male has to accept that the child is not his..When a child grows up, he has to know who his or her father In Artificial Insemination, fertilized eggs are left for time before being implanted WHY -To ensure that the process succeeded and the embryo is growing..To allow to be large enough to be easily implanted- CELL :01110983031 00201110983031 [email protected]  Advantages 1-Helps women who have blockage in their oviducts to be pregnant. 2-IF the male is unable to produce healthy sperms, sperms from a donor can be us. Disadvantages 1.Put the male and female under stress of surgical methods. 2. Expensive. 3.Usually many embryos are implanted, one is used while others are killed or used in researchers. Sex Hormones 1.Male sex hormone (Androgen). Female sex hormone (Estrogen). Example: Testosterone ( Male sex hormone). Produce primary sexual characteristics such as: 1. Development of sex organs. 2. Erection in case of stimulation. 3. Production of sperms. 2.Produce secondary sexual characteristics: 1. Rough voice (deep) 2. Growth of facial and pubic hair 3. Muscle development 4. Broad shoulders CELL :01110983031 00201110983031 [email protected] 1.Produce primary sexual characteristics such as A. Ovulation B. Menstruation 2. Produce secondary sexual characteristics A. Hips widen B. Breast increases in size C. High pitched voice 1.Fertility drugs 2.FSH / LH / clomiphene / clomid causes the ovaries to produce more eggs which increases the chance of fertilization. Female: Progesterone causes lining of uterus/ endometrium to thicken which increases chance of implantation. Male: Testosterone stimulates sperm production. CELL :01110983031 00201110983031 [email protected]