1. Evolution
Evolution – change in inherited characteristics/traits in a population over several generations
All organisms descend from a common ancestor or common gene pool
“Descent with Modification”
Only occurs when there is a change in allelic frequency (# of dominant v. #of recessive) in a given population over time
Genetic equilibrium = no evolution (means allelic frequencies are equal one generation to the next)

2. Adaptation – feature that is common in a population because it provides an improved function or behavior for survival
Gives a greater fitness (favorable trait)
Created by natural selection (survival of the fittest)
Can be structural or physiological
Examples: camouflage,
mimicry, toxicity
development,
echolocation,
resistance build up

3. Evidence of Evolution Fossil record Anatomy Embryology/developmental
Homologous structures
Analogous structures
Vestigial structures
Embryology/developmental
Biochemistry
DNA/amino acid sequence
Cytochrome C

4. Mechanisms of Evolution
1) Mutations – allows for greater variation and new variations
2) Migration – flow of genes in and/or out of a population (gene flow)
Immigration = movement into a population (increases allelic frequency)
Emigration = movement out of a population (decreases allelic frequency)
Creates variation
3) Non-random mating – eliminates variations (independent assortment and genetic recombination in meiosis)

5. Mechanisms of Evolution
4) Genetic drift – chance changes from generation to generation (affects small populations more)
Caused by disease, natural disasters, climate change, recessive traits
Must have genetic variation
5) Natural selection (most significant cause) – choosing of a certain variation over another
Survival of the fittest
Variation + differential reproduction + heredity = natural selection

6. **Survival of the Fittest**
Natural Selection
Fitness – describes how good a particular genotype is at leaving offspring in the next generation
**Survival of the Fittest**
Determined by environment/habitat
Includes ability to survive, find a mate, and produce offspring
3 types of Natural selection:
Stabilizing – favors the average individuals (hybrids)
Directional – favors one extreme of the trait
Disruptive – favors both extremes of the trait

7. Artificial selection – purposely choosing desired traits of an organism and reproducing them
Done by farmers and breeders
Creates purebred lines
“Selective breeding”
Coevolution – 2 or more species evolve together or cause each other to evolve
Predator/prey or parasite/host
Competitive species
Mutualistic species

8. Microevolution – evolution on a small scale (a single population)
House sparrows adjusting to North American climate
Mosquitos evolving to global warming
Insects/bacteria evolving resistance to pesticides/antibiotics
Macroevolution – evolution on a large scale
Multiple species
Large time scale
Speciation – formation of a new species
Species – group of organisms that can interbreed and produce fertile offspring

9. Causes of Speciation
Geographic isolation -  population is prevented from interbreeding by a physical barrier
when rivers change course, mountains rise, continents drift, roads are built, part of a forest cut down
what was once a continuous population is divided into two or more smaller populations.
Reproductive isolation -  behaviors and physiological processes that prevent the members of a population or species from producing fertile offspring
Can be a difference in mating ritual, non-compatible genitals, or produces infertile offspring

10. Rates of Speciation
Gradualism – change occurs over a long period of time (several generations/100’s of years) Punctuated equilibrium – change occurs quickly, in rapid burst followed by periods of genetic equilibrium

11. Patterns of Evolution
Divergent evolution – two species that once were similar evolve to be very different
Called adaptive radiation when
caused by differing habitat
Darwin finches
Supported by homologous structures
Convergent evolution – two unrelated species that once were different evolve to be
very similar
Dolphins and sharks
Supported by analogous structures