BIO 150
Spring 2000
Evolutionary theory, evidence of evolution
- Darwin's theory of natural selection:
3 inferences based on 5 observations
- observation 1: great reproductive potential of species
- observation 2: populations tend to remain stable
- inference 1: struggle for existence among individuals in
a population, with only a fraction of offspring surviving each generation
- observation 3: individuals in a population vary
- observation 4: much of this variation is heritable
- inference 2: survival is not random, but depends in part
on the hereditary constitution of surviving individuals, individuals whose
characteristics best fit them to the environment are more likely to leave
offspring than less fit individuals
- inference 3: unequal ability of individuals to survive
and reproduce will lead to a gradual change in the population
- Artificial selection
- examples: wild mustard (cabbage, cauliflower, etc), selective
breeding of dogs
- Points to remember about natural selection
- population is smallest unit that can evolve
- natural selection can amplify or diminish only heritable
variations
- specifics of natural selection are situational- a change in
environmental conditions may result in selection of different
characteristics
- Natural selection in action- examples
- guppies with different predators ( killifish prey mainly on small
guppies, pike-cichlid prey mainly on large guppies)
- finches on Galapagos Islands, change in beak size depending on
food availability
- Evidence of evolution
- biogeography- geographical distribution of species
- fossil record- succession of fossil forms
- comparative anatomy- e.g. homologous structures
- comparative embryology
- molecular biology
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Last modified April 20, 2000
BIO 150 - Unit IV - First Lecture /
Michael S. Rosenberg