Big Idea III: Evolution by natural selection is key to understanding life on Earth.

Harvard professor E.O. Wilson (b. 1929) proposed a two-idea suggestion for understanding biology. All organic processes are ultimately obedient to the Laws of Physics and Chemistry. Most scientists believe that all living systems and processes evolved by natural selection. This emphasizes the importance of evolution and natural selection to understanding life on Earth today. Natural selection is based upon the principles that:

1. organisms produce more offspring than can survive,
2. individuals compete for resources,
3. individuals have variationsVariation:
   The differences among individuals in a population. that could make them better (or less) able to survive and reproduce, and
4. the individuals that reproduce contribute to the next generation.

The process of natural selection through time can be easily observed through the fossil record and by observing the adaptations, complexity, and diversityDiversity:
The variety of species in a sample, community, or area. of living species. For more discussion on this topic, see the section How Evolution Works: Natural Selection.