Why do you think most complex animals and flowering plants use sexual reproduction, while many simple organisms, like yeast and hydra mainly reproduce asexually? [Pg. No. 208]

Most complex animals and flowering plants use sexual reproduction because it produces genetic variations among offspring. These variations improve the chances of survival and adaptation in changing environments. Since complex organisms have specialised body systems and longer life cycles, genetic diversity is important for their evolution and survival.
Simple organisms such as yeast and hydra mainly reproduce asexually because it is a faster, simpler and energy-efficient process. It allows them to produce large numbers of offspring quickly under favourable conditions.