(i) Organisms such as algae and fungi switch to sexual mode of reproduction during adverse conditions because asexual reproduction produces a large population that may not survive due to lack of resources. Sexual reproduction brings variations among the individuals, that might help the individuals to better adapt to the changed calamities and to survive. This ensures the continuity of species.

(ii) The period during which an organism grows to attain sexual maturity is called juvenile phase in animals. In plants, it is known as vegetative phase.