There are many ways in which particular survival adaptations are selected:
Directional Selection:
Eliminates one extreme variation from an array of possible phenotypes. Results in a shift towards the other extreme.
Selection acts to eliminate both extremes of an array of phenotypes. Results in an increase in individuals exhibiting an intermediate phenotype.
Disruptive Selection
Selection acts to remove the intermediate phenotypes favoring the extreme phenotypes:
Directional Selection:
Eliminates one extreme variation from an array of possible phenotypes. Results in a shift towards the other extreme.
Directional Selection
Stabilizing Selection:Selection acts to eliminate both extremes of an array of phenotypes. Results in an increase in individuals exhibiting an intermediate phenotype.
Stabilizing Selection
Disruptive Selection
Selection acts to remove the intermediate phenotypes favoring the extreme phenotypes:
Disruptive selection
Selection can result in various phenotypic changes in respect to evolution.
Convergent evolution:
- This occurs when species evolve into a common phentoypic form due to a common need. For example the diagram below portrays a shark, icthyosaurus, and a dolphin. These are fish, reptile ands mammal respectively (very different families of animals). Yet they all have a torpedo body shape, pectoral, caudal and dorsal fins. This is based on their common need to swim rapidly in an aquatic environment.
Divergent evolution.
- occurs when species evolve in several directions away from a common ancestor. This happens usyally to fill a vacant ecological niche. Also known as adaptive radiation.
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