1. Organisms reproduce and create new individuals of their kind. This is essential for perpetuation of species.
2. Information for inheritance of features from parents to next generation is present within chromosomes, in the form of DNA.
3. The DNA is information source for making proteins, which if changes will change the original body design.
4. Thus, for reproduction, each organism must first make copies of its DNA, so that the daughter cell produced can have its copy of DNA.
5. However, this DNA copying mechanism is not always fool-proof.
6. Any minor change in DNA, during copying, results in variation, which is the basis for evolution.
7. This variation is important for survival of species over time.
8. Different organisms use different methods of reproduction, depending on their body design.
9. Unicellular organisms may reproduce by fission. The parent cell may split into two daughter cells in any plane (e.g., Amoeba) or in specific plane (e.g., Leishmania). This is known as binary fission.
10. In some cases, as in Plasmodium, the parent cell may divide into many daughter cells - this is multiple fission.
11. Multicellular organisms with simple body organisation may break into small pieces, where each piece may grow into complete organism. This is observed in spirogyra and is known as fragmentation.
12. However, multicellular organisms with cell differentiation, when cut in small pieces, may regrow into complete organism with the help of specific cells, e.g., Planaria and Hydra. This process is known as regeneration.
13. Yeast and Hydra may grow a bud from their body, which can detach and mature into a complete organism. This is known as budding.
14. Many plants can give rise to new plants through their vegetative parts as roots, stem and leaves. This is known as vegetative propagation.
15. Tissue culture, is use of small tissues or cells from growing tip of plant to produce a new plant in artificial conditions.
16. In many fungi, like Rhizopus, spore formation takes place in spore sacs called sporangia. These spores, being thick walled, survive harsh conditions and can grow into a complete organism under favourable conditions.
17. All such methods of reproduction that do not involve fusion of male and female gametes are collectively termed as asexual modes of reproduction.
18. Sexual mode of reproduction involves combining of DNA from two different individuals thereby resulting in faster variations.
19. During sexual reproduction, two germ cells fuse to form zygote, giving rise to a new individual. Germ cells are produced as a result of special cell division called meiosis, which results in halving of chromosomes number. The chromosome number is restored after fusion.
20. Reproductive parts of angiosperms are located in the flower. Stamen is the male reproductive part and pistil is the female reproductive part.
21. Stamen consists of an anther and filament. Pollen grains are produced in the anther.
22. Pistil which is present in the centre of a flower is made of three parts. These parts are — swollen bottom part is the ovary, middle elongated part is the style and the terminal part which may be sticky is the stigma.
23. Transfer of pollen grain from anther to stigma is termed as pollination. Pollination is of two types: self-pollination and cross-pollination. When the pollen grain is transferred to stigma of same flower or to any other flower growing on same plant is termed as self- pollination. Transfer of pollen grain from anther of one flower to stigma of another flower growing on another plant of same species is termed as cross-pollination.
24. On reaching the suitable stigma, pollen grain germinates, carrying the two male gametes in pollen tube.
25. The first male gamete fuses with the egg cell, present in the embryo sac resulting in the formation of zygote.
26. The second male gamete fuses with secondary nuclei and result in formation of primary endosperm nucleus. This is known as double fertilisation.
27. After fertilisation, the ovule develops and converts into a seed containing embryo. The embryo is the future plant and when it is provided with suitable conditions like water, air and optimum temperature, it develops into a seedling.
28. The ovary grows rapidly and ripens to form a fruit. The fruit encloses the seeds. The seed contains embryo which has a plumule and a radicle. Radicle gives rise to root and plumule gives rise to shoot.
29. In humans, during adolescence, many morphological and physiological changes occur in bodies of both males and females.
30. The body of males become muscular, hair start growing on face, armpits and groin. These changes are brought about by hormones secreted by endocrine gland like testis, that produces testosterone.
31. Similarly in females during adolescence their breasts start enlarging, their hips become broader and menstrual cycle starts. These changes are due to hormones like FSH, LH, oestrogen and progesterone.
32. The male and female gametes’ production begins in respective reproductive organs i.e., testis and ovary, during puberty.
33. During reproductive age of male which last his life time, sperms or male gametes are produced.
34. However in females, the onset of menstrual cycle (menarche) signals production of female gamete ova. Production of ova stops in female when she reaches the age of 45-50 years. At this stage, the menstrual cycle stops and is referred to as menopause.
35. Testis are located in scrotum. Sperms are carried out from testis through vas deferens which unites with urethra. Prostate gland and seminal vesicles pour their secretions so that sperms are in fluid medium for easier transport.
36. At the time of birth, the ovaries contain thousands of immature eggs, which start maturing on reaching puberty.
37. One egg is released each month by one of the ovary, which travels from fallopian tube into the uterus. Each month, the uterus prepares itself for receiving and implanting zygote. It increases blood supply and thickens the wall.
38. The sperms are deposited into the vagina, during sexual intercourse and they swim towards the oviduct, where if ovum is present, then successful fertilisation will take place, resulting in formation of zygote.
39. The fertilised egg (zygote) begins to divide to form a ball of cells called embryo which gets implanted to the uterus wall where it continues to develop organs to become foetus. This implantation happens with the help of placenta.
40. Placenta helps the embryo to get nutrition and oxygen from mother’s blood and also in removal of wastes from growing embryo.
41. The child is born after nine months development within the mother’s uterus, as a result of contractions of uterine muscles.
42. In case, the egg is not fertilised, the lining of uterus slowly breaks and comes out through the vagina as blood and mucous. This cycle takes place roughly every month and is known as menstrual cycle and the flow of blood and mucous is termed as menstruation.
43. Certain diseases spread through sexual act. These include bacterial diseases like syphilis, gonorrhoea and viral infections such as warts and HIV-AIDS.
44. Transmission of such diseases can be prevented by using condom, a covering over penis during intercourse.
45. To prevent unwanted pregnancy, certain methods are adopted by both male and female. These contraceptive devices fall into three categories :
(i) Mechanical
(ii) Physiological
(iii) Surgical.
46. Use of condoms, copper-T are mechanical devices. Use of hormonal pills by female change hormonal balance and prevents release of eggs.
47. Surgical methods include vasectomy in males and tubectomy in females. In vasectomy, the vas deferens is blocked while in tubectomy, fallopian tube is blocked.

Reproduction : Related Mathematics !! 🙄🤔😑