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Speciation

horse. donkey. Speciation. mule. lion. Speciation. Defined : evolution of a new species Species : group of organisms that can interbreed and produce fertile offspring Different species rarely breed Interspecies breeding often results in sterile offspring Ex: Horse x Donkey = Mule

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Speciation

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  1. horse donkey Speciation mule

  2. lion Speciation • Defined: evolution of a new species • Species: group of organisms that can interbreed and produce fertile offspring • Different species rarely breed • Interspecies breeding often results in sterile offspring • Ex: Horse x Donkey = Mule • Ex: Lion x Tiger = Liger • Are horses & donkeys a different species even though they can produce offspring? tiger liger

  3. Causes of Speciation • 1) Geographic Isolation: mountains, rivers, canyons, oceans may separate apopulation • Natural selection allows favorable organisms to survive in different environments • Divergent Evolution: 1 species evolves into 2 or more with different characteristics

  4. Kaibab Squirrel (Grand Canyon)

  5. Divergent Evolution: 14 Species of Galapagos Finches Species A blown onto the islands from the mainland Because of the new environment, the birds adapt and change Species B spreads out across the new islands Species C spreads out across the islands Species C develops as the they begin to adapt to the new island Species D adapts to its new environment B A C D B C

  6. 2) Reproductive Isolation • Although not geographically separated, reproduction is prevented • 1) Different mating rituals • 2) Different sexual organs (lock & key) • 3) Sperm unable to fertilize egg • 4) Offspring created sterile (ex: liger and mule)

  7. 3) Genetic Drift • Defined: Changes in gene pool due to chance (not natural selection) • Gene pool: collection of genes within a population • Ex: Forest fire destroys 90% of a forest • Survival unrelated to advantageous traits • Survivors can only reproduce with other survivors • Therefore, the next generations might inherit different traits

  8. 4) Polyploidy • Defined: Having more than two copies of a chromosome • Diploid sperm (2n) + diploid egg (2n) = tetraploid (4n) offspring • Tetraploids behave as new species because they are unable to reproduce with original species • More common in plants because they can reproduce asexually by self-pollinating

  9. Other Patterns of Evolution • Convergent Evolution: different species evolve similar traits due to similar habitats • Ex: Fish and dolphins • Unrelated species with a similar environment

  10. Dragonfly Convergent Evolution

  11. Mimicry • Many structural and behavioral adaptations to copy/mimic the environment • Variations aid in their survival • Viceroy butterflies mimic the poisonous monarch • King snakes mimic the poisonous coral snake • Fish mimic the ocean floor • Insects mimic vegetation

  12. Coevolution • Defined: evolution of two or more interdependent species • Ex: Plants and Insects • Plants: provide insects with nectar • Insect: transfers pollen from one plant to another

  13. Quick Review • New species are created (speciation) when populations become isolated • A changing or new environment greatly affects natural selection • Evolution shapes life on earth

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