How do Organisms Reproduce?(Question Answer)

QUESTIONS

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

Answer: During reproduction, DNA copying ensures that each progenitor cell receives an equal number of DNA. As a result, the species retains its own characteristics. It maintains the continuity of life. In DNA copying, the offspring DNA strands are not exactly the same, resulting in diversity in the organism and contributing to evolution.

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

Answer: Different species of organisms maintain contact with a variety of environmental factors. This is very important to survive in the given situation. Any damage to the environmental condition of the population has a detrimental effect on the population. Only those organisms that are able to survive in such conditions and those which are adapted or suitable to the conditions of the organism can develop a population. So diversity is needed for species but not for individual organisms.

3. How does binary fission differ from multiple fission? 

Answer: Difference between binary fission and multiple fission are-

Binary Fission	Multiple Fission
1. In this process, the cell divides evenly into two parts.	1. In this process the cell splits into more than two parts.
2. No thick layer is formed around the cell	2. A thick layer is formed around the cell
3. Binary fission usually occurs under favorable conditions	3. Multiple fission can occur in any situation

4. How will an organism be benefited if it reproduces through spores? 

Answer: Reproduction by pollen can be beneficial for an organism because:

                 (1) The spores are covered with a sufficiently thick covering, so they can survive for many days even in adverse conditions.

                 (2) Spores can produce innumerable plants in a very short period of time.

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

Answer: The body structure of complex multicellular organisms is very complex. In their body certain cells combine to form tissues. These tissues form different organs, the organs form the organ system and all of them form the whole organism. Since the body structure of complex multicellular organisms has a very high organization, it is not possible to create new organisms by regeneration. This is because it is not possible to reconstruct the whole organism from any one part of the body.

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

Answer: From the roots or stems or leaves of some plants, new plants can be grown in suitable environment. For plants which do not produce seeds, Grafting and Layering methods are used in agriculture for the growing new plants. Plants that originate through vegetative propagation gives fruit early. Another advantage of vegetative propagation is that plants originating in this way are not only genetically identical but also have the same characteristics as their ancestors.

7. Why is DNA copying an essential part of the process of reproduction?

Answer: During reproduction, DNA copying ensures that each progenitor cell receives an equal number of DNA. As a result, the species retains its own characteristics. It maintains the continuity of life. In DNA copying, the offspring DNA strands are not exactly the same, resulting in diversity in the organism and contributing to evolution.

8. How is the process of pollination different from fertilization? 

Answer: There is a difference between pollination and fertilization. Pollination is an external process, fertilization is an internal process. Pollination results in the formation of pollen tube, and fertilization results in the formation of gamete.

9. What is the role of the seminal vesicles and the prostate gland? 

Answer: Both the seminal vesicles and the prostate gland secrete a fluid that forms part of the semen. The fluid from the testicles forms 60% of the semen and the fluid from the prostate gland forms 30% of the semen. This fluid makes the path smooth so that sperms can travel easily. This fluid also protects the semen from acid in the urethra. This fluid nourishes the semen with fructose, calcium and some enzymes.

10. What are the changes seen in girls at the time of puberty?

Answer: At the time of puberty lots of changes are seen in a girls body. Thick hair starts to grow in new parts of the body such as armpits and the genital area between the thighs, which can also become darker in colour. Thinner hair can also appear on legs and arms, as well as on the face. The skin frequently becomes oily and they might begin to develop pimples. Breast size begins to increase, with darkening of the skin of the nipples at the tips of the breasts. Also, girls begin to menstruate at around this time. 

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

Answer:  The mother’s body is designed to undertake the development of the child. Hence the uterus prepares itself every month to receive and nurture the growing embryo. The lining thickens and is richly supplied with blood to nourish the growing embryo. 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 uterine wall. It contains villi on the embryo’s side of the tissue. On the mother’s side are blood spaces, which surround the villi. This provides a large surface area for glucose and oxygen to pass from the mother to the embryo.

12. If a woman is using a copper-T, will it help in protecting her from sexually transmitted diseases?

Answer: Copper-T is only a contraceptive method. It is placed in the uterus to stop pregnancy. But it does not protect from sexually transmitted diseases.

EXERCISES

1. Asexual reproduction takes place through budding in 

(a) amoeba. 

(b) yeast. 

(c) plasmodium. 

(d) leishmania. 

Answer: (b) yeast. 

2. Which of the following is not a part of the female reproductive system in human beings? 

(a) Ovary 

(b) Uterus 

(c) Vas deferens 

(d) Fallopian tube 

Answer: (c) Vas deferens 

3. The anther contains 

(a) sepals. 

(b) ovules. 

(c) carpel. 

(d) pollen grains. 

Answer: (d) pollen grains.

4. What are the advantages of sexual reproduction over asexual reproduction? 

Answer: In asexual reproduction, the new generation of organisms are almost identical to their parents because they have the same genes in their bodies as their parents. Genetic variation in the asexual reproduction is not possible. This hinders the evolution of the organism.

         In case of sexual reproduction, children are identical with their parents but not completely identical. This is because children get some genes from their mothers and some genes from their fathers. Due to the combination of different genes of mother and father, there are genetic differences in the body of the child. Thus sexual reproduction leads a population to greater diversity. Therefore, a species (animal or plant) can adapt quickly to changes around it. It contributes to the evolution.

5. What are the functions performed by the testis in human beings? 

Answer: The formation of germ-cells or sperms takes place in the testes. These are located outside the abdominal cavity in scrotum because sperm formation requires a lower temperature than the normal body temperature. Testes also play a role in the secretion of the hormone, testosterone. In addition to regulating the formation of sperms, testosterone brings about changes in appearance seen in boys at the time of puberty.

6. Why does menstruation occur? 

Answer: If the egg is not fertilised, it lives for about one day. Since the ovary releases one egg every month, the uterus also prepares itself every month to receive a fertilised egg. Thus its lining becomes thick and spongy. This would be required for nourishing the embryo if fertilisation had taken place. If fertilization does not occur this lining is not needed any longer. So, the lining slowly breaks and comes out through the vagina as blood and mucous. This is why menstruation occurs in females. It usually lasts for about two to eight days.

7. Draw a labelled diagram of the longitudinal section of a flower. 

Answer:  

8. What are the different methods of contraception? 

Answer: Different methods of contraception are-

1. Mechanical Barrier- One category of contraception is the creation of a mechanical barrier so that sperm does not reach the egg. Condoms on the penis or similar coverings worn in the vagina can serve this purpose. 

2. Hormonal Treatment- Another category of contraception is by changing the hormonal balance of the body so that eggs are not released and fertilization cannot occur. These drugs commonly need to be taken orally as pills. However, since they change hormonal balances, they can cause side-effects too. 

3. Surgical Method-  Contraceptive devices such as the loop or the copper-T are placed in the uterus to prevent pregnancy. If the vas deferens in the male is blocked, sperm transfer will be prevented. If the fallopian tube in the female is blocked, the egg will not be able to reach the uterus. In both cases fertilization will not take place. Surgical methods can be used to create such blocks.

9. How are the modes for reproduction different in unicellular and multicellular organisms? 

Answer:

Reproduction mode in unicellular organism	Reproduction mode in multicellular organism
1.  In unicellular organism asexual reproduction takes place.	1.  In multicellular organism sexual reproduction takes place.
2. Only one organism is required.	2. Two organisms are required.
3.  There is no special organ for reproduction	3. There is special organ for reproduction.

10. How does reproduction help in providing stability to populations of species? 

Answer: Reproduction is the only way for an organism to increase its population. Therefore, it is especially helpful in maintaining the stability to the population of an organism. The process of reproduction helps the organism to survive on the planet and prevents the organism from becoming extinct on the planet. In this way the organism maintains a balance between the ratio of birth to death. Reproductive processes lead to diversity and evolution in the organism.

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

Answer: Pregnancy is caused by sexual intercourse. The pregnancy of a woman depends entirely on the physical and mental condition of the woman. If the woman is not ready for pregnancy then her health will suffer a lot. Therefore, contraceptive methods are used to avoid unwanted pregnancies. In addition, contraceptive methods are used to control the population.