Evidence for Evolution
1. Fossil Record
2. Anatomoy
3. Embryology
4. Biochemistry
Forces/Mechanisms of Evolution
- Natural/artificial selection
- Mutations/variations
- Migrations/gene flow
- Genetic drift
Trends in Evolution
- Coevolution
- Convergent evolution
- Adaptive radiation
- Extinction:
- Gradualism vs. Punctuated equilibrium
- Speciation
Anatomy
Similar features that originated in a common ancestor, but now have different functions and/or
external structures (common ancestry, different function now) Example: front limbs of
human and bird:
Features that serve identical functions and look somewhat alike but do not share a common
ancestor (no common ancestor, but same function now) Example: wing of a butterfly and
wing of a bird:
Features that now seem to serve no useful function and are usually reduced in size, Structure
was useful in an ancestor, but no longer serves original purpose- so it has changed, Example:
human tailbone:
Word Bank
Homologous Structures
Vestigal structures
Analogous Structures
Forces/Mechanisms of Evolution
The study of shared features in young emrbyos suggest evolution from a common ancestor:
When one extreme trait is picked over another (example: environment picking dark green frogs
over light green)
When a moderate or intermediate trait is selected (example: environment picking a medium
green color instead of light green or dark green)
When both of the extremes are chosen (example: environment picks light green and dark green
and eliminates medium green)
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Migration/Gene Flow
Embryology
Genetic Drift
Directional selection
Stabilizing selection
Disruptive selection
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Movement of individuals in and out of a population which introduces new traits:
Random loss of alleles/variation throughout generations, due to “failed” mating
A change of two or more organisms in close association with each other (two organisms
changing according to one another):
Animals developing similar feature due to environment and not common ancestor:
Species split into seperate species from an original ancestor due to different environments:
When all members of a species die off or no longer reproduce:
Species slowly and steadily changes through small changes (slow evolution):
Long periods of stability in a species are “punctuated” (interrupted) by periods of rapid
evolution (fast evolution)
Creation of new species, Occurs when two populations have bee reproductively isolated:
Word Bank
Speciation
Coevolution
Extinction
Punctuated Equilibrium
Convergent Evolution
Gradualism
Adaptive Radiation