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Macroevolution. Biology. Speciation. Review: Microevolution. Changes in genetic frequencies for a trait, in a population. H.W.E. Conditions. Our equations are great for: Finding allele frequencies: p + q = 1 Finding genotype frequencies: p 2 +2pq + q 2 = 1
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Macroevolution Biology
Review: Microevolution • Changes in genetic frequencies for a trait, in a population.
H.W.E. Conditions • Our equations are great for: • Finding allele frequencies: p + q = 1 • Finding genotype frequencies: p2 +2pq + q2 = 1 • Showing microevolution if values change over time • When would allele frequencies not change over time?
H.W.E. Conditions • No Mutations • No new genotypes/phenotypes • Very large population size • No minor population disruptions (genetic drift) • Isolation from other populations • No immigration/emigration (gene flow) • Random Mating • No picky females choosing one allele over another • No natural selection • No environmental pressures selecting one allele over another
Macroevolution (Speciation) • Formation of a new species
Definition of a Species • Population of interbreeding organisms
Ensatina salamanders • http://video.pbs.org /video/1300397304/
Isolation Mechanisms • Isolate two populations, isolate two gene pools: • Mutations in one pop. will not transfer to the other • Ex: House mouse of Madeira, Portugal
Habitat Isolation • Populations are geographically separated.
Behavioral Isolation Populations respond to different mating cues
Temporal Isolation • Populations breed during different times
Hybrid Sterility • Hybrid offspring is not fertile
Biological Species Concept • Defines a species as a population or group of populations whose members have the potential to interbreed with one another in nature to produce viable, fertile offspring, but who cannot successfully interbreed with members of other species
Limitations to BSC • Does not account for • Asexually reproducing species: bacteria • Fossil species: Trilobite
Studying the Unobservable • Direct Observation • Fossil Record • Comparing Structures • Molecular Analysis
1. Direct Observation • Pathogen Resistance: • Head Lice • Salmonella • Escherichia coli • Pseudomonas aeruginosa • Streptococcus pyogenes • Clostridium difficile, etc…
1. Direct Observation • Male guppies have variable colors • Colors attract mates • Colors attract predators • After many years of study: • Ponds with many predators produce drab ♂ • Ponds with few predators produce colorful ♂
1. Direct Observation • Ensatina Salamanders
2. Fossil Record • Shows the evolution of a species over time
2. Fossil Record • Homonid sp. fossils
3. Comparing Structures • Homologous Structure: • Similar body structures of different organisms • Show evolutionary relationships
3. Comparing Structures • Vestigial Structures: • Structures with NO known functions • Show remnants of evolutionary past
3. Comparing Structures • Homo sapiens • Appendix: previous stomach • Coccyx: previous tail • Wisdom teeth: previous herbivore • Ear muscles: previous limited head mobility • Plica semiluneris: previous nictitating eyelid • Goosebumps: (hair standing up to scare off predators) • Palmer grasp reflex: (infants grasp mother after birth)
4. Molecular Analysis • Compare similarities in genetics • DNA nucleotides • Chromosomes • Protein sequences
4. Molecular Analysis • Humans and Chimpanzees have ~98% of the same genes & a common ancestor