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Reproduction
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- 2. What is reproduction? Reproductionsmeans producing new living things.
- 3. Why reproduction isimportant? Reproduction is important to keep the population growing. Without reproduction species would have become extinct.
- 4. Types of reproduction 1.Asexual reproduction 2. Sexual reproduction
- 5. Asexual reproduction Inasexual reproduction there is only one parent All the offsprings are identical to the parents. They have the same genes. They are called clones. Example: Bacteria, amoeba, potato,Hydra
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- 8. Sexual reproduction Insexual reproduction there are two parents. The parents have sex organs that produce sex cells or gametes. In male animals gametes or sex cells are called sperms. They are made in male sex organs called testes. In female animals female gametes or sex cells are called eggs or ova. The eggs are made in sex organs called ovaries.
- 9. Sexual reproductioninvolves the joining together of male gamete and female gametes (sex cells). The offsprings are not identical to the parents. They show much more genetic variation than asexual reproduction. Half of the genes come from the father and half from the mother.
- 10. Differences between asexualand sexual reproduction: Sexual reproduction Asexual reproduction 1. Results from fusion of male and female gametes 1. Does not involve fusion of male and female gametes 2. It requires two different parents 2. Requires only one parent 3. The offsprings produced are not identical to the parents 3. Offsprings produced are identical to the parents- both genetically and morphologically 4. Causes genetic variation and leads to genetic diversity 4. Do not cause genetic variation and hence does not lead to any genetic diversity 5. Most animals reproduce sexually 5. Algae,fungi and bacteria reproduce asexually
- 11. Male reproductive organs Male reproductive organs: 1.Testes 2. Scrotum 3. Prostate gland 4. Seminal vesicles 5. Vas deferens 6. Penis 7. Urethra
- 12. The mainfunction of the testes is producing and storing the sperm. They're also important for producing testosterone hormone. Location of testes: The testes are contained in the scrotum.
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- 14. Male reproductive organs Epididymis: a duct behind the testis which transports sperm to the vas deferens. Vas deferens/ Spermatic duct: the duct which transports sperm from the testicle to the urethra. Seminal vesicles: A pair of glands that secrete seminal fluid present in the semen. Prostate: Gland that secretes prostatic fluid that nourishes the sperm. Scrotum: a pouch of skin containing the testicles. Cowper’s gland: Secretes fluid that adds to the semen.
- 15. Cowper’s gland Seminal vesicles Forms fluid that nourishes the sperms Prostate gland Composition of semen : Sperm and fluid from these three glands
- 16. Female reproductive organs Female reproductive organs are called 1. Ovaries 2. Uterus 3. Fallopian tubes/ Ovi ducts 4. Vagina
- 17. Ovaries: Theovaries produce and release eggs into the fallopian tube at the mid-point of each menstrual cycle. They also produce the hormones oestrogen and progesterone. Location: lower abdomen Fallopian tube: A pair of tubes along which eggs travel from the ovaries to the uterus. Fertilization takes place here.
- 18. Uterus: Theuterus is a hollow muscular organ that holds the developing baby or fetus during pregnancy. Vagina: The vagina is the elastic muscular canal that connects the uterus to the outside world.
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- 20. Sex cells orgametes: Male sex cells or gametes are called sperm. Sperms are produced in the testes (singular testis). Semen is the male reproductive fluid that contain up to 10 per cent of sperm. The rest consists of enzymes, vitamin C, calcium, protein, sodium, zinc and fructose sugar.
- 22. Structure of asperm Structure of a sperm: Contains head, mid-piece and tail. Head: contains the nucleus with the genetic material from the father , surrounded in front by a thin sac called the acrosome, which contains enzymes used for penetrating the female egg. Middle-piece contains mitochondria. Tail helps the sperm to move.
- 23. Structure of egg The egg or ovum (pl. ova) is circular in shape. Larger in size than sperms Inside the cell there are nucleus containing genetic information from the mother. It contains yolk as food store. It has jelly coat that also protects the ovum.
- 24. Differences between spermand egg Sperm Egg Small Large Swim using tail Can not move much No food store have a food store Millions produced much fewer made
- 25. Fertilisation Fertilisation happenswhen the nucleus of sperm joins with the nucleus of the egg. A fertilized egg or zygote is produced. The fertilized egg then divides into a ball of cells called embryo.
- 27. Types offertilization: 1. External fertilization: Fertilization taking place outside the body. Eg. fishes 2. Internal fertilization: Fertilization taking place inside the female body. Eg. Human,lion
- 34. Adolescence Adolescence -the period of life when a child develops into an adult. Age: 10-14 years You become an adolescent on the onset of puberty. Adolescence finishes when you stop growing at 18. Why does this changes occur? – Due to hormones.
- 35. Puberty Puberty -the period during which adolescents reach sexual maturity and become capable of reproduction.
- 36. The pituitaryglands produces hormones that make the sex organs active. Secondary sexual characteristics in male: Testes produces testosterone which causes- 1. the testes start to make sperm 2. hair starts to grow on the face and body 3.the voice deepens 4. the muscles develop
- 37. Secondary sexualcharacteristics in female: The ovaries start making oestrogen. 1. the ovaries start to release eggs. 2. hair starts to grow on parts of the body. 3. the breast develops. 4. the hips widen. 5. period starts.
- 38. Menstrual cycle Menstruation-Monthly periodic shedding of the lining of the uterus is called menstruation. Also known as period. Ovulation- Release of mature egg from the ovary into the oviduct is called ovulation.
- 41. Menstrual Cycle Startingat the puberty, the female reproductive system undergoes a regular sequence of events, repeated every 28 days. This is known as the menstrual cycle. Sequence of events during one menstrual cycle- From day 1 to 5 of the menstrual cycle , the endometrial lining of the uterus breaks down. This is known as menstruation. The pituitary gland secretes follicle stimulating hormone (FSH) ,which stimulates the development of the follicles in the ovaries. Usually one follicle ripens to become Graafian Follicle in one of the ovaries during each cycle.
- 42. Menstrual Cycle FSHalso stimulates the follicles in the ovary to secrete oestrogen. 3. Oestrogen thickens the endometrial wall of the uterus. The level of oestrogen peaks between 7-14 day of the menstrual cycle. 4.A high level of oestrogen in the blood inhibits FSH production, preventing the ripening and growth of more follicles. 5.Oestrogen also stimulates the pituitary gland to secrete Luteinising hormone (LH). 6.LH causes the release of the egg cell from a matured follicle, this is known as ovulation.
- 43. Menstrual cycle 7.LHalso causes the formation of corpus luteum, the remaining part of the follicle (yellow body). 8. Corpus luteum secretes progesterone. 9. Progesterone keeps the uterine lining thick and well supplied with blood, preparing it for the implantation of the embryo. It inhibits both FSH and LH. Progesterone level peaks between day 14-21 of the cycle. 10. Around the last few days of the cycle, the corpus luteum starts to degenerate. It stops releasing progesterone. This leads to the breakdown of the endometrial wall, starting another cycle.
- 44. summary Day 1– Menstruation begins (bleeding) Day 5 – Menstruation is usually ended Day 14 – Ovum has matured and bursts out of the ovary Day 15 – After 24 hours the egg is gone Day 26 – In the absence of fertilization, estrogen/progesterone levels drop and the endometrium lining breaks down Day 28 – Menstruation begins again.
- 46. Menstrual cycle FSH(Follicle Stimulating Hormone): Secreted from pituitary gland Function: Causes development of the follicle and egg. Stimulates ovary to produce oestrogen. Oestrogen: Secreted from ovary. Function: Causes thickening of the lining of the uterus and prevents more eggs from developing. Stops pituitary to make more FSH.
- 47. Menstrual cycle Luteinisinghormone: Secreted from pituitary gland. Function: Makes the ovary to release egg (ovulation). Converts empty follicle into yellow body. Progesterone: Secreted by corpus luteum (yellow body). Function: Makes the uterus lining thicker.
- 48. Menopause When periodpermanently stops in female it is called menopause and it usually occurs at the age of 45-55 years of age.
- 49. Corpus luteum/ yellowbody After ovulation, the Graafian follicle develops into a corpus luteum. The corpus luteum produces hormones that prepare the body for pregnancy. It secretes progesterone, a hormone that causes thickening of the uterus. Progesterone also inhibits the secretion of FSH and LH – thus prevents development of any further follicles.
- 51. Fertile period Duringthis period, sperms in vagina are likely to cause fertilization. Day 11-16 of the menstrual cycle After its release from an ovary, an egg can survive for 1-2 days in the reproductive system. For a 28 day cycle, ovulation occurs around day 14. Hence an egg can survive from day 14 till day 16.
- 52. Fertile period Duringthis time, it travels along the oviduct. Sperms can live for 3-4 days in the female reproductive system. This means that sperm released into the vagina on around day 11 can fertilise the ovum and bring about pregnancy. Hence, fertilization is possible from around day 11 to day 16. This period is known as the fertile period. The rest of the days make up the infertile period of the menstrual cycle.During this time,sperms released into the vagina are less likely to fertilise the ovum.