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How Diversity Evolves

How Diversity Evolves. Macroevolution. The evolution of large scale diversity Evolutionary novelties Wings, feathers, brain sizes Speciation: origin of new species. What is a species?. The morphological species concept: if it looks like a duck, and quacks like a duck…. What is a species?.

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How Diversity Evolves

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  1. How Diversity Evolves

  2. Macroevolution • The evolution of large scale diversity • Evolutionary novelties • Wings, feathers, brain sizes • Speciation: origin of new species

  3. What is a species? • The morphological species concept: if it looks like a duck, and quacks like a duck…

  4. What is a species? • The morphological species concept: Mature leaves of arrowhead plants (Sagittaria sagittifolia)

  5. What is a species? • The biological species concept: groups of interbreeding natural populations that are reproductively isolated from other such groups. • What problems might exist with this definition?

  6. What is Speciation? • For speciation to occur, populations must attain reproductive isolation. • Genetic Divergence: when populations become reproductively isolated.

  7. Reproductive Isolating Mechanisms • Any heritable features that prevent interbreeding between populations • Isolating mechanisms can be physical (body form), physiological (body function), or behavioral • Isolating mechanisms can be prezygotic or postzygotic. Note: a zygote is a fertilized egg.

  8. Reproductive Barriers

  9. Prezygotic Isolation • Temporal (reproduce at different times)

  10. Prezygotic Isolation • Behavioral (courting behaviors are different) Bird courtship behavior include visual, acoustic and tactile rituals that identify members of the same species.

  11. Prezygotic Isolation • Mechanical (differences in reproductive organs) • Plants and their pollinators

  12. Prezygotic Isolation • Habitat (same area but different habitats) • Microhabitats of Manzanita in Nevada

  13. Prezygotic Isolation • Gametic Mortality (egg & sperm incompatibility) Correct chemical signal needed for successful fertilization

  14. Postzygotic Isolation • If fertilization does occur the embryo is often weak and dies. • In others, hybrids are vigorous but sterile. Mules are produced by a male donkey and female horse.

  15. Mechanisms of Speciation • Allopatric speciation: geographically isolated by a physical barrier. • Sympatric speciation: species form within home range of an existing species.

  16. Allopatric Speciation • “allo” = different; “patric” = lands • Antelope squirrels and the Grand Canyon

  17. Evidence for Allopatric Speciation

  18. Allopatric Speciation • Archipelagos island chain and adaptive radiation • low competition and predation • abundant habitats and resources

  19. Sympatric Speciation • “sym” = together • Cichlids of Lake Barombi Mbo • Many species by feeding modes (open water, bottom feeders, shoal feeders)

  20. Sympatric Speciation • Polyploidy • How does this happen? • Improper separation during meiosis & mitosis • 50% of all flowering plants are polyploidy • Animal problems

  21. The Evolution of Wheat

  22. Evolutionary Trees and Rates of Change • Trees summarize information about the relationship among species over time. • Two types of models: • Gradual model: branches at slight angles to show slow changes over time • Punctuation model: horizontal branches show abrupt speciation followed by stable conditions

  23. Evolutionary Trees and Rates of Change

  24. Macroevolution and Exaptation • Biological novelties • Structures that evolved in one context becomes adapted for other functions

  25. Macroevolution and “Evo-Devo” • Genetic changes in developmental biology • Homeotic genes • Control timing, rate, and spatial patterns in embryos • Subtle changes can have profound effects • Paedomorphosis Axolotl

  26. “Evo-Devo” Research

  27. Macroevolution and Earth’s History

  28. Macroevolution and Historical Events

  29. Evolution Today?

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