The Theory of Evolution Biology 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  #3: Homologous Structures: Body parts which form in similar ways during embryonic (before birth) development.  These parts share similar, but different arrangements and functions. Vestigial Structures = Parts that have lost their function in an organism and therefore are reduced in side.

Evidence of Evolution  #4: Similarities in Early Development: Many embryos look especially similar during development.