1 / 12

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)

jensenc
Download Presentation

Speciation & Rates of Evolution

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  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

More Related