1. What is the importance of DNA copying in reproduction?
Ans. (i) DNA copying is important for causing variations.
(ii) DNA copying causes cell division which is essential for reproduction.
2. Why is variation beneficial to the species but not necessary for the individual?
Ans. Variations help organisms to survive in adverse conditions. Sudden and dangerous changes that occur in the environment often cause the whole population to perish. But organisms with variations survive even in those conditions. These organisms increase population through reproduction. This way the species is saved. Thus variations are important for survival and maintenance of individuals. As for individual, variation is not necessary because individual can survive when it is well adapted to its niche. For an individual it is not good to remain different from the individuals of the same species.
3. How does binary fission differ from Multiple Fission?
Binary Fission Multiple Fission
(i) A single cell divides into two equal and similar (i) A single cell divides into many equal and
Cells. Similar cells.
(ii) This happens in normal conditions. (ii) This happens in adverse conditions.
(iii) It happens in a single plane. (iii) This happens in different planes.
4. How is organism benefitted by spore formation or Sporulation?
Ans. Sporulation is a method of asexual reproduction which is very popular in single organisms. Many spores develop together at one time in this process. These spores scatter far apart after the sporangium bursts due to internal pressure. Under moist and favourable conditions spores germinate to produce hyphae that later develop into mycelia. Thus the population grows suddenly and the existence of species is maintained even after the death of some individuals.
5. Can you think of reasons why more complex organisms cannot give rise to new individuals through regeneration?
Ans. Regeneration is possible only through specialized cells. Living beings with complex structure contain many types of cells. These cells are specialized for many different types of works. None of these cells have capacity to regenerate under natural conditions and to produce new organs.
6. Why is vegetative propagation practiced for growing some types of plants?
(i) Because these plants have capacity to reproduce through their vegetative parts.
(ii) Plants developed through vegetative propagation bear flowers and fruits in a short period of time.
(iii) Plants grown through this process contain all the parental traits.
7. Why is DNA copying an essential part of the process of reproduction?
Ans. DNA molecules have important information regarding body design, physiology etc. of an organism. On the basis of these coded information the growth, development and all the other processes of organism take place. The DNA is transferred in the new cells also as a result of DNA copying. Without DNA a cell cannot survive. Hence, DNA copying is an essential part of reproduction.
8. How is fertilization different from pollination?
Ans. (i)In pollination pollen grains are transferred from the pollen sac to the stigma of Gynoecium but in fertilization two male gametes fuse with two female gametes found inside the ovary.
(ii) Pollination is an external process whereas fertilization is an internal process.
9. What are the roles of seminal vesicle and the prostate gland?
Ans. The seminal vesicle secretes seminal fluid which nourishes the sperms. It also acts as a medium for the transfer of sperms. Prostrate secretes prostrate fluid. It is an alkaline fluid. Both the seminal fluid and prostate fluid mix along with sperms to form semen.
10. What changes are seen in the girls at the time of puberty?
Ans. Following changes are seen in girls at the time of puberty –
(i) Secretion of sex hormones start which usually makes the skin oily.
(ii) Development of mammary glands and hips take place.
(iii) Hair growth starts on and around sex organ.
(iv)Menstrual Cycle starts.
11. How does embryo get nourishment inside mother’s body?
Ans. The embryo inside the mother’s uterus gets nourishment through the blood of the mother. It remains attached to the uterus through placenta. All the nutrients contained inside the blood of the mother pass to the embryo through placenta.
12. If a woman is using copper –T, will it help in protecting her from sexually transmitted diseases? Discuss.
Ans. Copper –T can check fertilization and thus pregnancy. It is not a disease preventive device. However, it can provide partial safety from sexually transmittable diseases.