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Speciation & Rates of Evolution

Speciation & Rates of Evolution. Biology 101B. Reproductive Isolation Two Types:. 1. Prezygotic Isolation Prevents reproduction by making fertilization unlikely Geographic isolation- separated by barrier (river, canyon)

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Speciation & Rates of Evolution

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  1. Speciation & Rates of Evolution Biology 101B

  2. Reproductive IsolationTwo Types: 1. Prezygotic Isolation • Prevents reproduction by making fertilization unlikely • Geographic isolation- separated by barrier (river, canyon) • Temporal- mating occurs at different times for different species (trout, fireflies, some flowers) • Behavioral isolation- no sexual attraction or communication- use different mating songs or calls • Mechanical- structural differences- sex organs “don’t fit” • Gametic- gametes fail to unite & create viable offspring

  3. Reproductive IsolationTwo Types: Liger 2. Post-zygotic Isolation • Prevents the development of fertile adults • Hybrid inviability- zygote fails to develop • Hybrid sterility- offspring are sterile & cannot produce offspring • EX: Liger: cross between a male lion and a female tiger creates liger which is usually sterile • EX: Mule: cross btwn donkey & horse. Tigon

  4. Reproductive Isolation leads to SPECIATION • Speciation: Process by which some members of a sexually reproducing population change so much that they can no longer produce fertile offspring with members of the original population.

  5. SpeciationTwo Types: • Allopatric Speciation (Geographic isolation) • Physical barrier divides one population into two or more populations • Mountain ranges, channels btwn islands, rivers, canyons, lava flows • 2 different species evolve from same ancestral species • EX: Kaibab squirrel & Abert squirrel separated by Grand Canyon Activity 23.2 Allopatric Speciation

  6. SpeciationTwo Types: • Sympatric Speciation • Species evolves into a new species without a physical barrier • Some insects and plants evolve this way • Most likely due to mutation.

  7. Patterns of Evolution • Adaptive Radiation • Many species evolve from a common ancestor • Occurs as a result of formation of new habitat or other ecological opportunities • Also called divergent evolution • May follow mass extinctions • EX: cichlid fish in Lake Victoria • EX: Darwin’s finches

  8. Patterns of Evolution • Coevolution • Species evolve in close relationships with other species • Mutualism • Ex: flowers & their insect pollinators • Predator-prey • Ex: cheetahs & antelope • Ex: plant chemical defenses & insects

  9. Patterns of Evolution • Convergent evolution • Unrelated species evolve similar traits even though they live in different parts of the world. • Similarity in environment has led to evolution of similar traits. • EX: Madagascar aye-aye and New Guinea striped opossum both have elongated middle fingers. Live separately but have same structure

  10. Rates of EvolutionTwo Types: • Gradualism • Small, gradual steps • Traits remain unchanged for millions of years • Punctuated Equilibrium • Abrupt transitions • Seen in fossil record • Rapid spurts of genetic change caused divergence quickly

  11. What are some current trends in evolution? 1. Natural Selection • Antibiotic resistance in bacteria • Pesticide resistance in insects • Industrial melanism- peppered moths changed due to pollution. • Generally, organisms that are more general in their needs survive. A species that requires a specific food source or habitat will be less able to change. 2. Artificial Selection • Genetically modified foods • Selective breeding in dogs Antibiotic Use & Evolution

  12. HIV and drug resistance • http://www.pbs.org/wgbh/evolution/library/10/4/l_104_10.html

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