Lesson #17 of 18 in the Brain Makeover collaboration with Professor James Trefil/George Mason University, the 76ers Cheerleaders and the Science Cheerleader. See Brain Makeover Series.
17. All forms of life evolved by natural selection.

Scientists divide the development of life on Earth into two segments: chemical evolution, which involves the development of life from inorganic materials, and evolution by natural selection, which describes the process by which that early life form produced the diversity of modern life. The latter is what people associate with Charles Darwin and usually mean by the term ‘evolution’.

Evolution by natural selection depends on two things: first, that there are variations within populations (so that, for example, some rabbits can run faster than others) and, second, competition between individuals (so that fast rabbits are more likely to survive and reproduce). Over time, this selection process produces new species.

Evidence for evolution by natural selection comes from the fossil record and from the examination of genes in the DNA of modern life forms.