Punctuated Equilibrium Verses Gradualism. What Drives Evolution.

Punctuated Equilibrium

Verses Gradualism

What Drives Evolution

1-Isolation

TemporalGeographicBehavioral

2-Artificial Selection

Did not drive evolution!!!

2-Natural Selection

2-Natural Selection

3-Variation & Heritability

Sources of Genetic Variation

Mutations – 300 mutations in our DNA that are different from our parents mutations• Only matter if they can be passed to next generation – skin cancer

Sexual Reproduction – remixes the genes your parents provide into new combinations of paired alleles

Lateral Gene Transfer – only in single celled creatures but significant to all evolution and current resistance to drugs.

Single Gene (allele selection) Vs Polygenic Traits (phenotype selection) & how natural selection works on them.

Type of Selection for Polygenic Traits: Directional / Stabilizing / Disruptive

Founder Population

Bottleneck

Genetic Drift

Evolution Vs Genetic Equilibrium

Genetic Equilibrium = allele frequency in a gene pool does not change – sexual reproduction does not change change frequency.

Hardy Weinberg principle = predicts allele frequency for a population and if it is wrong than it is likely that evolution is taking place.

Disturbances to Equilibrium:1. Nonrandom mating – mate selection2. Small Population Size3. Immigration & Emigration4. Mutations5. Natural Selection6. Look at Darwin’s Finches pages 496-497

Molecular Evolution

Molecular Clocks• Uses rates of neutral mutations in stretches of DNA to estimate the time that

two species have evolved independently of each other – page 499

Gene Duplication• Gene Families such as Hox genes• New copy genes evolve without changing the original

Hox Genes: Mutations to this gene is significant to the body plan

Dark Matter: Switches

Microevolution & Macroevolution

Mass Extinctions5 recorded mass extinctions1. Ordovician (440mya) - 50% of animal families2. Devonian (360mya) - 30% of animal families3. Permian (250mya) - 50% of animal families, including 95% of

marine species4. Triassic (210mya) - 35% of animal families5. Cretaceous (65mya) - 60% of animal species

Recovery Time6. Ordovician - 25 million years7. Devonian - 30 million years8. Permian/Triassic - 100 million years9. Cretaceous - 20 million years

Many other minor extinctionsBackground Extinction

Mass Extinctions

Current - Holocene Extinction