How come organisms that are able to resist the stresses of desert life are rare in milder environments?
1 Answer
Evolutionary niches.
Explanation:
All organisms alive today have been successful in the evolutionary game. Any animal species in a given location (very important) undergoes evolutionary natural selection processes to select the kinds of traits that help in their survival in that given location. Traits that are not useful, don't get adopted by the species - ones that are, become part of their survival package of traits.
Say, a particular kind of lizard in Australia. It evolves cold bloodless to help survive in desert environment and the ability to shed heat when they need to. They might also evolve the ability to be very frugal with water and not release too much. Their color might be selected to blend in with say the surrounding brown rocks. This is called phenotypical expressions.
So, now if you take that lizard to the Amazon rainforest its got all the wrong kind of phenotypical traits for that particular environment. There may be Amazon lizards that have evolved traits that allow them to survive in that rainforest environments, but the Aussie lizard does not, so would probably die out.
