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Speciation: Last Lecture!!

Speciation: Last Lecture!!

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Speciation: Last Lecture!!

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  1. Speciation: Last Lecture!!

  2. What’s a species? • “Kind of living thing” • Species: plural and singular word • Biological species concept: Similar individuals capable of interbreeding to produce fertile offspring

  3. What’s a species? • Evolutionary species concept: Organisms distinct from others that form single line of descent.

  4. Naming Species • Binomial system: Species’ scientific name 2 words • Bi=“2” nomen=“name” • First: “genus” • Second: “specific name” • Together make up scientific name.

  5. Naming Species • Ex: Our species • Homo sapiens • Italics (not English: it’s Latin) • Homo sapiens means “wise human” or “wise being.”

  6. Naming Species • Ex, Melanotrichus boydi • Insect in California Plant: Streptanthus polygaloides

  7. Classifying Species • Classification: Group species into larger units • Species into Genus • Genera (plural of genus) into Family • Families into Order • Orders into Class • Classes into Phylum • Phyla (plural of phylum) into Kingdoms • Kingdoms into Domains.

  8. Classifying Species • Ex: “perky”, the domestic cat. Do I look excited or what?

  9. Organisms • Ch. 4 (Cells): archaea, bacteria, protist, fungi, plant, and animal cell traits (review these)

  10. How species form? • Speciation: Evolution of new species • In general, different species if: • 1) differ in appearance due to genetic traits • 2) cannot produce fertile offspring (“reproductive barrier” prevents joining gene pools) • (Biological species concept).

  11. Reproductive barriers • Premating barriers: stop interbreeding before mating. Types: • 1) Temporal isolation: flowering/mating at different times

  12. Reproductive barriers • Premating barriers: stop interbreeding before mating. Types: • 2) Habitat isolation: occupy different habitats

  13. Reproductive barriers • Premating barriers: stop interbreeding before mating. Types: • 3) Behavioral isolation: Mating signals differ

  14. Reproductive barriers • Premating barriers: stop interbreeding before mating. Types: • 4) Mechanical isolation: Parts don’t fit Shells of snail species may coil in different directions. Shown (a), two coil left and one coils right. (b) Two snails with matching coils can mate (c) Snails with mismatched coiling cannot mate: mismatch keeps genitals (arrow) apart.

  15. Reproductive barriers • Postmating barriers: after mating. Types: • 1) Hybrid inviability: hybrid dies

  16. Reproductive barriers • Postzygotic barriers: after gametes join. Types: • 1) Hybrid inviability: hybrid dies • 2) Hybrid sterility: hybrid can’t produce gametes • Ex: horse and donkey (mule: sterile). Liger

  17. Geographic Isolation • Separation by “geographic barrier” • Populations “geographically isolated:” gene pool split. Change over time • Allopatric speciation: populations geographically separated

  18. Geographical Isolation • Ex, Grand Canyon ground squirrels • Species on each side differ.

  19. Geographic Isolation • Ex: Desert pupfish in western U.S.

  20. Geographic Isolation

  21. Geographic Isolation • Ex: Desert pupfish in western U.S. • Some endangered: one spring!.

  22. Sympatric speciation • New species form (populations not separated) • Ex (plants): polyploidy • Increase in chromosome number

  23. Sympatric speciation • Ex: bread wheat • Nondisjunction chromosomes causes doubling and ability to be fertile T. aestivum (one of the common bread wheats) Triticum monococcum (einkorn) T. tauschii (a wild relative) Unknown species of wild wheat T. turgidum (wild emmer) 14AA X 14BB 14AB 28AABB X 14DD 42AABBDD cross-fertilization, followed by a spontaneous chromosome doubling

  24. Speciation: Smooth or Jerky? • Gradualism: Species diverge slowly over time • Punctuated equilibrium: Change rapid, then slow. extinction (branch ended before present) new species branch point (a time of divergence, speciation) a new species branch point (a time of divergence, speciation) dashed line (only sketchy evidence of presumed evolutionary relationship) a single lineage a single lineage

  25. Adaptive Radiation • Explosion of speciation: one to many extinction (branch ended before present) new species branch point (a time of divergence, speciation) a new species branch point (a time of divergence, speciation) dashed line (only sketchy evidence of presumed evolutionary relationship) a single lineage a single lineage

  26. Adaptive Radiation • Often on islands • Ex: Galapagos finches.