=> When a single parent is involved in reproduction, then it is called Asexual Reproduction.
=> Reproductive organs in males and females are different. In females reproductive organs are ovaries, oviduct and uterus.
=> Ovaries produce female gamete called Ovum and male gamete called Sperms are produced by Testes.
=> Ovum and Sperm fuse to form egg called Zygote. The process of fusion of ovum and sperm is called Fertilization.
=> Embryo is formed from the zygote by repeated divisions, which grows in the uterus of the female in case of internal fertilization. Embryo grows into foetus when it gets into well developed limbs.
NCERT (CBSE) Textbook Exercise Solved
Q.1: Explain the importance of reproduction in organisms.
Ans: Reproduction is very important for the organisms. The organisms reproduce to produce young ones like them. It helps to carry on their generation. If reproduction does not take place, no living being will survive on the earth. Had the process of reproduction not been there then all the plants and animals would have become extinct. Secondly, special characters of an organism are carried over to its next generation through reproduction only.
Q.2: Describe the process of fertilization in human beings.
Ans: Human beings reproduce sexually. In human beings fertilization takes place inside the female body (internal fertilization). Males eject sperm inside female bodies. Sperms and ovum fuse to form the fertilized egg called zygote. This process in which the ovum and sperm fuse to form zygote is called Fertilization. During this process the nucleus of the sperm fuses with the nucleus of the ovum thus forming a single nucleus. In this way zygote is formed with a single nucleus, this completes the process of fertilization.
Q.4: Indicate whether the following sentences are True (T) or False (F):
(a) Oviparous animals give birth to young ones.
(b) Each sperm is a single cell.
(c) External fertilization takes place in frog.
(d) A new human individual developed from a cell is called gamete.
(e) Egg lay after fertilization is made up of a single cell.
(f) Amoeba reproduces by budding.
(g) Fertilization is necessary even in asexual reproduction.
(h) Binary fission is a method of sexual reproduction.
(i) A zygote is formed as a result of fertilization.
(j) An embryo is made up of a single cell.
Ans: (a)-F (b)-T (c)-T (d)-F (e)-T (f)-F (g)-F (h)-T (i)-T (j)-F.
Q.5: Give two differences between a zygote and a foetus ?
Ans: Differences between a zygote and a foetus are given below:
=> Zygote is formed of a single cell while foetus is made up of many cells.
=> Zygote does not have well developed limbs; foetus has well developed and identifiable limbs.
=> Zygote is formed by the fertilization of sperms and ovum; foetus is formed by the repeated divisions of the zygote.
Q.6: Define asexual reproduction. Describe the two methods of asexual reproduction in animals.
Ans: Asexual reproduction is that type of reproduction in which only single parent is involved. Asexual reproduction takes place by different methods like Budding, Binary fission etc.
Budding – This type of reproduction takes place in Hydra and Bacteria. A part of the organism starts bulging out. Slowly it grows and develops into a separate individual.
Binary fission – In this type of reproduction, a single organism gets divided into two. This type of reproduction takes place in Amoeba. The nucleus of the Amoeba gets divided into two followed by division of their bodies, each part getting one nucleus and developing into a separate individual.
Q.7: In which female reproductive organ does the embryo get embedded ?
Q.8: What is metamorphosis ? Give examples.
Ans: The transformation of the larva into adult through drastic changes is called metamorphosis.
Q.9: Differentiate between Internal Fertilization and External Fertilization.
Ans: Internal fertilization takes place inside the body of the female while the external fertilization takes place outside the body of the female. In case of the internal fertilization sperms are ejaculated inside the female’s body by the male while in external fertilization sperms are discharged in open.