It rains, water moves and erodes the land and creates valleys and rivers.
It is body composition! Np Welcome :P
The change in the environment affected how the organism would evolve to be so that it could survive. the term for that is survival of the fittest, and only the fittest would be able to survive the conditions of its surrounding environment. hope this answered your question. :)
Common mistakes and misconceptions
Natural selection is a mechanism, or cause, of evolution. Adaptations are physical or behavioral traits that make an organism better suited to its environment. Heritable variation comes from random mutations. Random mutations are the initial cause of new heritable traits.
