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natural selection

Tags
eco
cegep/3
Word count
203 words
Reading time
2 minutes

Adaptation of organisms to the environment by competition
Ant. artificial selection, e.g. breeding dogs

Mechanism:

  • Phenotypic variation: individuals of a population vary
  • Genetic variation: some of the differences are inheritable
    • <= mutation
  • Overproduction: species tend to produce more offsprings than can survive
  • Competition: individuals must compete for limited resources
    • Food
    • Territory
    • Mate
  • Differential success: the most fit survives and reproduces

[!abstract] fitness
Ability to survive and to reproduce

Types

Directional selection

Trait evolves towards one extreme

[!example] Evolution of horse towards larger size and one toed

[!example] Industrial melanization of moths
Environment becomes darker => moths become darker

Disruptive selection

Trait evolves towards both extremes

[!example] Adaptive radiation
Rapid evolution of

[!example] Batesian mimicry
Mimicry where a harmless species mimics the warning signals of a toxic species

[!example] Evolution of seedcracker birds towards two beak sizes

Stabilizing selection

Trait evolves towards the center

[!example]+ Sickle cell disease
Homozygous dominant: suffers from sickle cell
Homozygous recessive: suffers from malaria
Heterozygous: protected from both
=> evolution of humans in malaria regions to be heterozygous

[!abstract] Heterozygote advantage
Genetic advantage of being heterozygous for a specific trait

Contributors

Changelog