EARTH 7 Lecture Notes - Lecture 5: Genetic Drift, Selective Breeding, Group Selection
Important Vocab
Species: a group of viably interbreeding organisms
Lineage: a species through time
Speciation: when lineages split
- One lineage splits into two...and so on…
Evolution
- Change of species over time
- Not Darwin’s idea
- Lamarck’s ideas on evolution were already well known in Darwin’s day
Darwin’s most important ideas:
Common descent with modification
- All living organisms are related, descending from a single common ancestor
- Diversity is the result of bifurcation of lineages (speciation)
- Similarity is the result of close ancestry
- So central to biology and so well supported, that today this has become essentially
synonymous with evolution
- Evolution =/= natural selection
- Evolution - a process
- Natural selection - one (very important) mechanism explaining that process
- (other mechanisms: sexual selection; genetic drift; historical contingency; structural and
developmental processes and constraints, group selection, etc.)
Natural selection follows from three observations
1. Variation in a species
a. Sources of genetic variation:
i. sexual reproduction
ii. Changes in dna
2. Differential survival and reproduction
a. Often brutal in nature (a revolutionary concept).
3. Heritability of Variation
a. Variation genetically controlled
b. Offspring resemble parents
Artificial selection - analogous
Darwin very bold predictions:
- Fossil record should include transitional forms
- Age of earth and life must be immense
Transitional Forms:
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