Speciation, extinction, phylogeny, and taxonomy

Notes

Result: Different allele frequencies from original population. ⸻ D. GENE FLOW Movement of alleles between populations. Example: Bird migration between populations. Effect: Increases genetic diversity. ⸻ E. GENETIC RECOMBINATION Occurs during meiosis. Creates new gene combinations. Sources: * Crossing over * Independent assortment ⸻ 3. SPECIATION Definition Formation of new species. ⸻ Biological Species Concept Species: Groups capable of reproducing and producing fertile offspring. ⸻ Special Case: Hybrids Mule Horse × Donkey Usually sterile. ⸻ Liger Lion × Tiger Often infertile. ⸻ Zonkey Zebra × Donkey Usually infertile. ⸻ Types of Speciation Allopatric Speciation Geographic isolation. Example: Island populations. Most common. ⸻ Sympatric Speciation No geographic barrier. Example: Polyploid plants. ⸻ Parapatric Speciation Adjacent populations diverge. Example: Grass species near mines. ⸻ Peripatric Speciation Small isolated population. Closely linked to founder effect. Example: Island colonizers. ⸻ 4. EXTINCTIONS Natural Background Extinction Rate Normal extinction occurring continuously. ⸻ Five Mass Extinctions 1. Ordovician (~444 MYA) Cause: Glaciation Result: ~85% marine species ...