(a) Why do organisms like algae and fungi shift from asexual mode of reproduction to sexual mode?

(b) What is a juvenile phase in organisms?

(a) Algae and fungi are organisms with the simpler organization having an asexual mode of reproductions, they shift to a sexual mode of reproduction during the onset of adverse conditions for survival. Because sexual reproduction helps in variation and by variation these organisms can adapt to the adverse conditions and help them to survive the adverse conditions, thereby ensuring continuity of the species.

(b) There are many phases in the life of organisms. One of the phases is known as a juvenile phase. Juvenile phase is a period of growth between birth and sexual maturity. After this phase, the organisms start reproducing sexually and attain a level of maturity. In plants, this phase is known as Vegetation phase.