The Theory of EvolutionBiology B/Evolution

Important Concepts

Natural Variation = Differences among individual organisms of the same species.

Exists in all species

Is essential in allow for natural selection

Artificial Selection (Selective Breeding) = Humans purposely mate specific organisms to combine beneficial traits.

Artificial Selection

Important Concepts Continued…

Struggle for Existence = Members of each species compete constantly for food, water, space and protection.

Due to this struggle, not all members of a species will survive to reproduce.

Fitness = The ability of an organism to survive and reproduce in its particular environment.

Adaptation = Any inherited characteristic that increases an organism’s chances for survival.

Important Concepts Continued…

Natural Selection = Individuals who are the most “fit” are most likely to survive and reproduce, thereby carrying their traits into the next generation.

This idea is also known as “survival of the fittest” This occurs without human control or direction

Descent with Modification = Over long periods, natural selection results in a large scale change the structure of organisms of a species.

Common Descent = All species, living and extinct, originally came from common ancestors.

Evidence of Evolution

#1: The Fossil Record: By examining fossils from long ago to more recent times, one can view how a species changed over time.

Evidence of Evolution

#2: Geographic Distribution of Living Species:

Species living in different areas have different, but similar characteristics.

This suggests that similar environmental pressures resulted in similar pressures of natural selection.

Evidence of Evolution

Evidence of Evolution

#4: Similarities in Early Development: Many embryos look especially similar during development.