Chapter 22: Darwinian Natural Selection Flashcards
Darwin’s observations
- Organisms are not static
- Organisms are well-matched to environment
- Individuals of a population vary in their traits
- Offspring inherit traits from their parents
- All species are capable of producing more offspring than the environment can support
- Due to lack of resources, many offspring die
- Natural selection only acts on heritable traits
Artificial selection
the identification by humans of desirable traits in plants and animals, and the steps taken to enhance and perpetuate those traits in future generations
Darwin’s inferences
- Individuals with favorable, inherited traits survive at a higher rate than those with unfavorable traits
- because artificial selection can lead to large changes, natural selection should be capable of modification over thousands of generations
Clarifications
- Individuals do not evolve; populations do
- natural selection occurs because of interaction between individual and environment
- Natural selection only acts on heritable traits
- New favored traits come at a cost
Advantage of traits depends on…
Environment
If environment changes, selection may lead to…
Changes in a population
Support for evolution by natural selection
- Direct observational evidence (guppies, DDT resistant mosquitoes, antibiotic resistance)
- Fossil record
- Homology (remodeling/modification)
- Biogeography
Direct observational evidence for evolution by natural selection
Guppies in Trinidadian river system
Advantage: bright color attracts females
Disadvantage: bright color attracts predators
DDT resistance in mosquitoes
DDT resistant mosquitoes survive and pass on their traits
Homology
Similar structures used in different ways (i.e. human arm vs. wing vs. flipper)
Biogeography
Geographical distribution of plants and animals
