Natural Selection

3.4.2 Explain how natural selection influences the changes in species over time.

Charles Darwin Known for his theory of evolution by natural selection. Galapagos Islands- where he observed species of animals and plants that are unique to the islands, but similar to species elsewhere (geographic isolation).

Natural Selection Occurs when organisms with favorable variations survive, reproduce, and pass their variations to the next generation. Organisms without variation are less likely to survive and reproduce. The environment is what is important in selecting adaptations. A hummingbird's long bill and tongue evolved to let the bird reach deep into a flower for nectar.

Geographic Isolation Can cause speciation. Speciation is the evolution of a new species that occurs when members of similar populations no longer interbreed to produce fertile offspring within their natural environment. For many centuries two populations of squirrels have been isolated by the Grand Canyon, one population on the north rim and one on the south. They have now evolved into two different species.