How Do Organisms Reproduce Class 10 Notes Science Chapter 8

Chapter at a Glance

1. Reproduction: The production of new organisms from the existing organisms of the same species is known as reproduction.

2. Types of reproduction: There are two types of reproduction- asexual and sexual:
(i) Asexual reproduction: Asexual reproduction is a type of reproduction by which offspring arise from a single organism, and inherit the genes of that parent only. It does not involve the fusion of gametes. Modes of a sexual reproduction used are binary fission, multiple fission, budding, spore formation, regeneration, vegetative propagation, fragmentation.

  • (a) Binary fission: It is the process in which a parent cell splits into two daughter cells of approximately equal size, e.g., Amoeba.
  • (b) Multiple fission: It is the process in which a nucleus of a parent cell divides several times by producing several nuclei, e.g., Plasmodium.
  • (c) Budding: It is a process in which a new organism develops from an outgrowth or bud due to cell division at one particular site, e.g., Hydra.
  • (d) Spore formation: In this method, the parent plant produces hundreds of tiny spores which can grow into new plants, e.g., Rhizopus.
  • (e) Regeneration: It is a process by which the organism is capable of regrowing certain body parts, e.g., Planaria.
  • (f) Vegetative propagation: It refers to the process of plant reproduction whereby a fragment of a parent cell is taken in order to produce more plants (clones), e.g., sugarcane.
  • (g) Fragmentation: It is a process in which a parent body breaks into fragments, each capable of growing independently into new organism, e.g., sponges.

(ii) Sexual reproduction: In sexual reproduction, a male gamete (germ cells) fuses with a female gamete to form a new cell called ‘zygote’. This zygote then grows and develop into a new organism in due course of time. When male gamete and female gamete fuse, they form a zygote and the process is known as fertilisation. Fertilisation is of two types: external fertilisation and internal fertilisation.

4. Sexual reproduction in flowering plants : Flower is meant essentially for sexual reproduction.
(i) Pollination: Pollination is the process in which pollen grains are transferred from the anther to stigma of the carpel.
It is of two types: self-pollination and cross-pollination.

  • (a) Self pollination: It is the pollination ofa flower bypollen from the same flower or from another flower on the same plant.
  • (b) Cross pollination: It is the pollination of a flower of one plant to the stigma of the flower of another plant of the same species.

In the fertilisation process primary endospermic nucleus is formed. After the fertilisation process, ovary developes into the fruit whereas ovules into the seed.

5. Reproduction in human beings: The sex organ in males are testes and ova in females.
(i) Male reproductive organ: It consist of a pair of testes, vas deferens, a pair of epididymis, a pair of ejaculatory duct, urethra, pairs of accessory gland.
(ii) Female reproductive organ: It consist of a pair of ovaries, a pair of fallopian tube, uterus, vagina, external genitalia, mammary glands and accessory glands.
(iii) Menstruation: Bleeding accompanied by discharge of soft tissue lining the reproductive tract is menstrual flow. It last for 3-5 days. Secretory phase lasts for 12-14 days.
(iv) Process offertilisation in female: Fertilisation process occurs in fallopian tube. In this process zygote is formed. In this process, umbilical cord is produced which is attached to foetus. During this process, two hormones oestrogen and progesterone are produced. Progesterone stops mensturation and prevents ovulation. The placenta protects the body against diseases. Due to contraction of uterine muscles young one is expelled and the phenomenon is called parturition.
After the age of 45-50 years menses stop and process is called menopause.

6. Reproductive health: Reproductive health is a state of complete physical, mental and social well-being and not merely the absence of disease, in all matters relating to the reproductive system and to its functions and processes.

7. Contraception: It is a deliberate use of artificial methods or techniques to prevent pregnancy as a consequence of sexual intercourse. The various contraceptive methods are:
(i) Mechanical barrier method: They prevent contraception by preventing either sperms from entering uterus or preventing implantation if fertilisation has occurred. The instruments used are condom, cervical cap, diaphragm
(ii) Hormonal method: They prevent eggs from being released from the
ovaries and also prevent sperm from entering into the uterus which prevent implantation, e.g., oral pills.
(iii) Chemical contraception: They are creams, jellies and foaming tables which are placed in vagina for killing the sperms at the time of coitus.
(iv) Surgical techniques

  • (a) Vasectomy: It is a process in which male vas deferens are cut and tied or sealed so as to prevent sperm from entering into the urethra, which prevents fertilisation of a female through sexual intercourse.
  • (b)Tubectomy: It is a process in which woman’s fallopian tubes are blocked and sealed, either of which prevents fertilised eggs from reaching the uterus for implantation.

8. Sexually transmitted diseases (STDs): It is a group of infections caused by different types of pathogens that are transmitted by sexual contact between a healthy person and an infected person. The sexually transmitted diseases are alsocalled venereal diseases (VDs), e.g., gonorrhoea, syphilis, trichomonas, genital warts, AIDS.

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