How do Organisms Reproduce?

Class 10 NCERT Science


1   What is the importance of DNA copying in reproduction?

Solution :

DNA (Deoxyribonucleic acid) is the genetic material found in the chromosomes, which are present in the nucleus of a cell. The DNA is the information site for making proteins and each specific type of protein leads to a specific type of body design. Thus, it is the DNA molecule that determines the body design of an individual. DNA carries the genes responsible for all the characters of the individual including physiological processes. Therefore, it can be concluded that it is the DNA that gets transferred from parents to offspring and makes them look and behave in a similar manner.DNA determines body structure and function

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

Solution :

Variations are beneficial to the species than individual because sometimes for a species, the environmental conditions change so drastically that their survival becomes difficult. For example, if the temperature of water increases suddenly, then most of the bacteria living in that water would die. Only few variants that are resistant to heat would be able to survive. However, if these variants were not there, then the entire species of bacteria would have been destroyed. Thus, these variants help in the survival of the species. However, all variations are not necessarily beneficial for the individual organisms.

3   How does binary fission differ from multiple fission?

Solution :

In binary fission, a single cell divides into two equal cells. Amoeba and Bacteria divide by binary fission.$\\$ $\textbf{Binary fission in Amoeba}$$\\$ In multiple fission, a single cell divides into many daughter cells simultaneously. Amoeba and Plasmodium divide by multiple fission.$\\$ $\textbf{Multiple fission in Plasmodium}$

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

Solution :

Spores are dormant and hardy structures produced by some organisms in order to tide over unfavorable conditions. There are many advantages, if an organism reproduces through spores.$\\$ $\textbf{Advantages of spore formation:}$$\\$ $\bullet $ Large numbers of spores are produced in one sporangium.$\\$ $\bullet $ Spores are distributed easily by air to far-off places to avoid competition at one place.$\\$ $\bullet $ Spores are covered by thick walls to prevent dehydration under unfavorable conditions.$\\$ It allows cells to germinate and form a new individual once favorable conditions return

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

Solution :

Simple organisms such as Hydra and Planaria are capable of producing new individuals through the process of regeneration. The process of regeneration involves the formation of new organisms from its body parts. Simple organisms can utilize this method of reproduction as their entire body is made of fewer and similar kind of cells in which any part of their body can be formed by growth and development.$\\$ However, complex organisms have organ-system level of organization. All the organ systems of their body work together as an interconnected unit. They can regenerate their lost body parts such as skin, muscles, blood, etc. However, they cannot give rise to new individuals through regeneration as a specific cell or tissue cannot give rise to completely different cell and tissue types. Therefore, it would not be possible to completely regenerate an entire new organism.