Biology - Class Twelve
REPRODUCTION IN ORGANISMS
NCERT Solution - Part-1
Question-(1) Why is reproduction essential for organisms?
Answer: Every organism has a definite lifespan after which the individual dies. But each organism needs to maintain the continuity of its species. Reproduction is the process by which an organism is able to continue its progeny. Hence, reproduction is essential for organisms.
Question-(2) Which is a better mode of reproduction: sexual or asexual? Why?
Answer: Both the modes of reproduction have their own pros and cons. Asexual reproduction takes less time and hence helps in producing numerous generations in a short time span. Asexual reproduction is exploited by farmers and horticulturists to produce better variety of crops in shorter time. However, asexual reproduction has minimum chances of variations. Sexual reproduction is quite complicated and hence takes more time to commence. But since it involves exchange of genes of two individuals hence there are more chances of variations in this mode of reproduction. As a result, evolution could be possible because of sexual reproduction. Thus, it can be said that sexual reproduction is a better mode of reproduction.
Question-(3) Why is the offspring formed by asexual reproduction referred to as clone?
Answer: The offspring formed by asexual reproduction is exact copy of its parent. Hence, the offspring formed by asexual reproduction is referred to as clone.
Answer: As per Darwin’s theory of evolution, useful characters are transferred to the next generation to enhance the chances of survival. This somewhat holds true during sexual reproduction. Hence, it can be said that offspring formed due to sexual reproduction have better chances of survival. But this statement has some exceptions. For example; bacteria are among the simplest organisms in terms of structure. Yet bacteria are known to survive the harshest conditions. Many bacteria have developed resistance to latest antibiotics which signifies their immense ability to survive. This may not hold true for even the most complex of animals.
Answer: Progeny formed from asexual reproduction are exact copy of their parent. Such a progeny gets the gene pool from a single parent and hence does not show variation. On the other hand, progeny formed from sexual reproduction can never be an exact copy of their parent. Such a progeny gets the gene pool from two parents and hence show variations. This is the reason, a person may resemble his father or mother but there will always be some subtle differences.