Students must go through these JAC Class 10 Science Notes Chapter 8 How do Organisms Reproduce? to get a clear insight into all the important concepts.
JAC Board Class 10 Science Notes Chapter 8 How do Organisms Reproduce?
→ Reproduction: A process by which an organism produces new organism of its own kind is known as reproduction.
- Reproduction unlike other life processes, is not necessary to maintain the life of an individual organism.
Reproduction involves creation of a DNA copy. - Variations formed during reproduction are the basis for evolution.
- Reproduction is linked to the stability of population of species.
- Variation is useful for the survival of species over time.
→ Asexual Reproduction : When a single parent is involved in the formation of new generations, without the fusion of gametes it is called asexual reproduction.
Types of Asexual Reproduction :
- Fission
- Budding (e.g., Hydra)
- Spore formation (e.g., Rhizopus)
- Regeneration (e.g., Planaria)
- Fragmentation (e.g., Spirogyra)
- Vegetative propagation.
→ Fission :
- Binary fission (e.g., Amoeba, Leishmania) and
- Multiple fission (e.g., Plasmodium).
→ Vegetative Propagation :
- Natural vegetative propagation and
- Artificial vegetative propagation.
→ Natural vegetative propagation example the adventitious buds developing from the tuberous roots of sweet potato, leaf margins of bryophvllum and normal buds (eyes) on the surface of potato tuber.
- Cutting
- Layering
- Grafting, etc., are the artificial methods for vegetative propagation.
→ Advantage of vegetative propagation : All the plants produced are genetically similar to the parent plant.
→ Sexual Reproduction : A mode of reproduction in which both sexes, male and female are involved to produce new generations is known as sexual reproduction.
Germ cells have half the number of chromosome and half the amount of DNA due to meiosis. When both male and female gamete are fused, there is reestablishment of the number of chromosomes and the DNA content in the new generation. This may be similar to their parents or may be recombined to some extent.
→ Sexual reproduction in flowering plant: Flower is the sexual reproductive organ of flowering plants. The stamen is male reproductive part and the carpel is female reproductive part in flower.
- Pollen grains are produced within the anther of stamen. Male gametes are produced within the pollen grain.
- Female gametes are produced within the ovule of ovary of carpel.
- Fertilised ovule is transformed into seed while fertilised ovary forms the fruit.
- The seed germinates to produce new plant (offspring).
→ Sexual reproduction in human:
- Boys generally attain puberty at the age of 13-14 years and girls attain it at the age of 10-12 years.
- Male gonad – testis, produces sperms as well as sex hormone – testosterone.
- Female gonad – ovary, produces ova as well as sex hormones – estrogen and progesterone.
Sex hormones are responsible for attaining sexual maturity.
→ Male reproductive system in human beings : A pair of testis, vasa deferentia, seminal vesicles, prostate gland, urethra, bulbourethral glands or cowper’s glands and penis. Male reproductive cells, i.e., sperms are tiny bodies that consist mainly of genetic material and a long tail.
→ Female reproductive system in human beings: A pair of ovary, a pair of oviduct (fallopian tubes), uterus, cervix and vagina.
- Female reproductive cell, i.e., egg cell/ovum is large and contains the nutrients.
- If the fertilisation does not occur, then the thick wall of uterus (endometrium) breaks down. The thick wall of uterus along with the blood vessels and dead ovum comes out through vaginal opening in the form of a bleeding known as menstruation. Menstruation lasts for 2 to 8 days.
→ Contraceptive methods used for the control of population :
- Mechanical barriers of contraception : The loop or the copper-T are used in females and condom for males.
- Chemical barriers of contraception : Oral pills for females. By changing the hormonal balance of the body, eggs are not released.
- Surgical methods : Vasectomy, i.e., vas deferens in male is blocked or tubectomy, i.e., fallopian tubes in female is blocked surgically. In both cases fertilisation will not take place.