CBSE Class 10 Science Important Questions Chapter 8 How Do Organisms Reproduce Part 4

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16. Draw a flow chart showing various types of reproduction with examples.

Ans.

Various types of reproduction

Various Types of Reproduction

Various types of reproduction

17. What is grafting? Why is it used in horticulture practices?

Ans. In grafting, cutting of a plant stem is attached to another rooted plant. The cutting of stem which is grafted on the other plant is scion and the rooted plant on which the cutting is grafted is called stock. The scion and stock are placed one over other and tied in such a way that there is no gap between them. The cambium activity takes place among them and they get joined. Grafting is used in plants which do not produce extensive roots.

18. What are the different methods of contraception?

Ans. Different methods of contraception are –

a) Barrier method – In this method, a device used to prevent the entry of sperms in the female genital tract example – Condom, Diaphragm, Cervical caps.

b) Chemical method – In this method certain drugs (containing hormones) are used by the females. These drugs are available in the form of pills. There are two kinds of pills commonly used for preventing pregnancies – oral pills and vaginal pills or creams.

c) Intrauterine contraceptive devices (IUCD’S) – IUCD like copper – T is placed in the uterus – IUCD prevent implantation of the fertilized ovum inside the uterus.

19. What is AIDS? Name its causal organism. Mention its symptoms.

Ans. AIDS is a sexually transmitted disease. Its full form is acquired immune deficiency syndrome. It is a viral disease, caused by human immune deficiency virus. Its symptoms are-

a) Destroys the immune system of body.

b) Persistent cough and fever.

c) Body attacked by other diseases like pneumonia, TB and certain cancers.

20. Explain vegetative reproduction through layering. Give examples.

Ans. It is a type of artificial vegetative reproduction in which a branch of the parent plant is buried in the soil. The portion of the branch which is in contact with the soil produces roots 24 and this rooted branch is called layer. Layer is then detached form the parent plant which acts as a new plant. Example – Jasmine.

21. What is the importance of DNA copying in reproduction?

Ans. DNA contains information for the inheritance of features from parents to next generation. DNA presents in nucleus of cells are the information source for making protein. If information is different, different protein will be made that lead to altered body design.

22. Why is variation beneficial to the species but not necessarily for the individual?

Ans. Variations are useful for the survival of species in changed environment situations. If a population of reproducing organism were suited to a particular niche and if the niche is drastically altered the population could be wiped out. However, some variations are present some species will survive. Thus, variation is useful to species but not the individual.

23. How does binary fission differ from multiple fissions?

Ans. Difference between binary fission and multiple fission:

Binary Fission and Multiple Fission
Binary fission and multiple fission

Binary fission

Multiple fission

Splitting of unicellular organisms like amoeba in to two equal halves during cell division is termed binary fission.

Division of single-celled organisms such as malarial parasites into many daughter cells simultaneously is termed multiple fission.

24. Can you think of reasons why more complex organism cannot give rise to new individuals through regeneration?

Ans. The reason is that complex organisms are not merely random collection of cells. Specialized cells are organized in them as tissues are organized in organs. These organs have to be placed at definite positions in the body. So, regeneration is not possible in multicellular organism.

25. Why is vegetative propagation practiced for growing some types of plants?

Ans. (i) Plants raised by vegetative propagation can bear flower and fruits earlier than those produced from seeds.

(ii) Such methods also make possible the propagation of plants such as banana, orange, rose and jasmine that have lost the capacity to produce seeds.

(iii) All plants produced by this method are genetically similar enough to the parent plant to have its all characteristics.

26. Why is DNA coping essential part of the process of reproduction?

Ans. DNA contains information for the inheritance of features from parents to next generation. DNA presents in nucleus of cells are the information source for making protein. If information is different, different protein will be made that lead to altered body design.

27. How does the embryo get nourishment inside the mother’s body?

Ans. The embryo gets nutrition from the mother’s blood with the help of a special tissue called placenta. This is a disc which is embedded in the wall of uterus. It contains finger-like projections villi on the embryo’s side of the tissue. On mother’s sides are blood spaces, which surround the villi. This provides a large surface area for glucose and oxygen to pass the mother to the embryo and waste products from embryo to mother.

28. Why does menstruation occurs.

Ans. When in human female if the egg is not fertilized, it lives for about one day. Since the ovary releases one egg every month, the uterus also prepares itself every month to receive a fertilized egg.

Thus, its lining becomes thick and spongy. This would be required for nourishing the embryo if had fertilized. However, this lining is not required any longer. So, the lining slowly breaks and comes out through the vagina as blood and mucous. This cycle takes roughly every month and is known as menstruation.

29. Draw a labeled diagram of the longitudinal section of a flower.

Ans.

Longitudinal section of a flower

Longitudinal Section of a Flower

Longitudinal section of a flower

30. What are the different methods of contraception?

Ans. various methods used for regulation of child birth can broadly categories as:

(i) Barrier methods: In this method, physical devices such as condom, diaphragm, cervical cap and copper-T are used.

(ii) Chemical method: use of spermicidal jelly by woman, oral pills and vaginal pills.

(iii) Surgical method: In surgical method, a small portion of vas deferens in male and the oviduct of female, is surgically removed or ligated. It is called vasectomy in male and Tubectomy in females.

31. What could be the reasons for adopting contraceptive methods?

Ans. The sexual act always has the potential to lead to pregnancy. Pregnancy will make major demands on the body and the mind of the woman and if she is not ready for it, her health will adversely affected. Therefore, adopting contraceptive methods are essential. Some contraceptive methods like condom also prevent spread of STDs and lethal diseases like HIV-AIDS.

32. Producing individuals by parents consume a lot of energy. So, why should an individual organism waste energy in the process, it does not need to stay alive?

Ans. Reproduction, unlike other life processes is not essential to maintain the life of an individual organism. But it is essential for providing stability to the population of species.

Maintaining the species is essential for maintaining balance in nature.

33. Blue prints of body design are stored in the DNA. Why?

Ans. The chromosomes present in the nucleus of a cell contain information for inheritance of features from parents to next generation in the form of DNA molecule. The DNA is the information source for making proteins. Thus, blueprints of the body design are stored in the DNA.

34. Why is variation beneficial to the species but not necessary for the individual?

Ans. Variation is beneficial to the species as it enables a species for its survival. A favourable variation makes an organism to live better in a changed environment and an unfavourable variation will not. So it is not necessarily true that a variation is beneficial to the individual always.

35. What is the advantage of reproduction though spores in the case of Rhizopus?

Ans. The spores are covered by thick walls that protect them until they come into contact with another moist surface and can begin to grow.

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