How evolution is branching?

Question

easy best answer

Answer 1

Each population of an existing species either merges back to other populations, dies out, or continues on as a distinct population.  Given enough time, and especially in different environments, members of a population will become incapable of interbreeding with members of other populations.  We call this population a new species.  Over time, one species becomes many in this way (or goes extinct).

Answer 2

Evolution is usually caused by changes in the environment.

A fun project might be to assume continued Global Warming  and predict the effect on various animals.

Evolution is also caused by random mutations of the genes.  Some of these are so bad that the individual dies, some are bad and could be considered as evolution in reverse, some are good which means the mutation makes the entity better able to use or survive the environment. Most mutations have no significant effect.

Many people think that human evolution means bigger brains and more intelligence.  IMO bigger and more intelligent brains are just one thing that makes one person different from another, they do not necessarily give an evolutionary advantage.