Short answer -Class 10 -Science- Biology-Chapter 7: How Do Organisms Reproduce

Class 10 -Science- Short answer  -Biology-Chapter 7: How Do Organisms Reproduce

Q1. Leaves of Bryophyllum fallen on the ground produce new plants. Why?

Ans :Leaves of Bryophyllum fallen on the ground produce new plants due to a process called vegetative propagation or adventitious plantlet formation. In Bryophyllum, specialized structures called plantlets develop along the margins of the leaves. When the leaves fall onto the ground, these plantlets have the ability to take root and develop into new individual plants. This form of asexual reproduction allows Bryophyllum to propagate and spread rapidly, even without the need for seeds or specialized reproductive structures.

Q2. What are the functions of the following in male reproductive system? a. Seminal vesicles b. Prostate gland

Ans :  a. In human males, seminal vesicles store sperms temporarily before ejaculation.

b. Both seminal vesicles and prostate gland add their secretions so that the sperms remain in a fluid which makes their transport easier and also this fluid provides nutrition.

Q3. or List any four methods of contraception used by humans. How does their use have a direct effect on the health and prosperity of a family?

Ans :  Three techniques to prevent pregnancy:

a. Mechanical barrier — male or female.

b. Taking oral pills/i-pill/saheli – changing the hormonal balance of the body so that eggs are not released.

c. Use of the loop or the Copper-T.

d. Surgical method – tubectomy / vasectomy Use of hormonal preparations is not meant for males.

Effect on Health and Prosperity:

a. Health of women is maintained

b. Parents can give more attention to children

c. More resources can be made available.

Q4. Give two examples each of the following: a. Plants having unisexual flowers b. Agents of pollination c. Physical changes on puberty that are common to both boys and girls.

Ans :  a. Papaya, watermelon

 b. Insects, air, water, etc.

c. (i) Appearance of pubic hair. (ii) Skin becomes oily and may develop pimples.

Q5. DNA content has the tendency to double itself during sexual reproduction due to combining of the genetic materials from the two parents. How the problem of DNA doubling can be solved to maintain the consistency of the genetic material throughout the species.

Ans: DNA doubling is always followed by cell division. Due to this special cell division, gametes form with half the content of DNA and single set of chromosomes. These gamete fuse to form zygote on fertilization. Thus the characteristic number of chromosome and the normal DNA content for a cell is regained. Thus the consistency of the genetic material throughout the species is maintained and for the same reason the chromosome number of the sexually reproducing parents and their offsprings is the same.

Q6. Justify the following statements:

a. Variation is beneficial for the species over a period of time.

b. New offsprings produced are similar to their parents but not identical.

c. Binary fission is different in Amoeba and Leishmania.

 Ans :  a. Variations help a population in the process of natural selection and accumulation of adaptations in a population. It leads to evolution of a species.

 b. Offspring, especially when produced sexually, have minor differences or variations among themselves hence they may not look identical. By virtue of them being from same species they look similar.

c. Binary fission in Amoeba is in any plane but in Leishmania it is in a fixed plane.

Q7. a.How do organisms reproduced by fission?

b. Write names of any two organisms which reproduce by this method.

 c. Differentiate between the fission of Leishmania and Plasmodium.

Ans: a. Cell division takes place which leads to creation of new individuals.

 b. Bacteria, Protozoa.

c. Leishmania — binary fission occurs in a definite orientation. Plasmodium — undergoes multiple fission,

Q8. What are sexually transmitted diseases? Name any one which is caused by bacteria and one caused by viral infection.

b. Mention any two methods to avoid such diseases.

Ans :a. Diseases that spread through the sexual contact are called sexually transmitted diseases.

 (i) Gonorrhoea or syphilis is caused by bacteria.

 (ii) Warts, HTV, AIDS is caused by virus.

b. (i) Use of condoms on penis.

Q9. Name one STD caused by a bacterial infection and one by a viral infection. How can these be prevented?

Ans: Gonorrhea and syphilis are caused by bacterial infection while HIV and Genital warts is a viral STD. In order to prevent STD’S,

• One must avoid having copulation with an unknown person or an infected person

• Always use protection

• Avoid any instances that include the transfusion of blood.

• Do not share infected needles or surgical instruments with an infected person

Q10. When is vegetative propagation used? Name any three methods of vegetative propagation.

Ans: Vegetative propagation is a form of asexual reproduction that occurs in plants.

There are certain parts of plants that possess the ability to get developed into a complete parent plant when they are grown under correct nutrition.

Plant parts such as roots, stem, leaves, buds flowers, anthers and ovary possesses the ability to get developed into a complete parent plant tassels possesses a special property called as “totipotency” which is responsible for this phenomenon.

Now there are certain methods of vegetative propagation which includes

• Grafting

• Cuttings

• Mound layering