Darwinian Natural Selection
A. Natural Selection as “the” mechanism that produces descent with
modification aka evolution – Darwin’s Four Postulates
1. Individuals within a spp. are variable
2. Some variations are passed on to offspring
3. More offspring produced than survive
4. Survival and reproduction are NOT random
Fitness = Winners @ survival and reproduction
Adaptation = modified traits or characteristics
Galapagos Finches on hypothesis testing, winners by a beak!
B. The Nature of Natural Selection
1. Acts locally, Functions globally – Individuals vs. populations
2. Acts on phenotypes, Functions on genotypes – Resulting change in
gene frequencies
3. Backward looking NOT forward – Product of environment for each
generation
4. Acts on existing traits – No spontaneous generation allowed
5. Not Perfect, does NOT prepare
6. Nonrandom, i.e., “Directed” and “Purposeful” but not progressive
No Higher or Lower forms; Complex and Simple are O.K.
7. Tautological? Nope, “Favorable” is still not random!
8. Acting on individuals includes altruistic behaviors, i.e., Kin Selection
C. NeoDarwinism – Includes the mechanism(s) for natural selection
1. Mutation – generates variability within a population
2. Genetics – Heritability or passing of traits to the next generation
3. Age of Earth is known – Thermonuclear decay gets factored in!
4. DNA structure is known – The double helix with semi-conservative
replication.
Lecture 3.1