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Macroevolution

Macroevolution. Macroevolution is the study of major biological changes evident in the fossil record Includes the following: Multiplication of species Origin of structures like feathers and large brains Diversification of species – like flowers

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Macroevolution

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  1. Macroevolution • Macroevolution is the study of major biological changes evident in the fossil record • Includes the following: • Multiplication of species • Origin of structures like feathers and large brains • Diversification of species – like flowers • Mass extinctions that lead to explosions -like the explosion of mammals after the dinosaurs became extinct

  2. speciation • Speciation is the origin of new species • Branching vs. non-branching • Branching – a lineage is split into two or more species • Non-branching – initial species becomes new species

  3. Anagenesis vs. Cladogenesis

  4. The Origin of Species • Biological species concept – groups of interbreeding natural populations whose members ONLY breed with each other to create fertile offspring. • What keeps members of different species apart?

  5. Reproductive Barriers • Prezygotic barriers – occur before conception • Post-zygotic barriers – occurs after conception

  6. Pre-zygotic Barriers • Temporal Isolation – mating or flowering occur at different time of the year/day Ex. Western spotted skunks breed in fall, while eastern spotted skunks breed in the late winter • Habitat Isolation – species living in the same region may occupy different habitats Ex. Some Garter snakes live in water/some on land • Behavioral Isolation-courtshiprituals are very specific Ex. Birds • Mechanical isolation-structuraldifferences in genitalia or flowers prevent copulation or pollen transfer Ex. Insects and flowers • Gametic isolation- male sperm cannot fertilize the egg

  7. Post-zygotic Barriers • Hybrid Inviability – hybrid zygotes fail to develop or reach sexual maturity • Hybrid Sterility – Hybrid individuals fail to produce young

  8. Speciation • When a population is somehow severed from the parent population and over time its gene pool is altered. • Allopatric and sympatric

  9. Allopatric speciation • Isolation is the result of a geographic barrier • Ex. Galapagos finches • True speciation only occurs if the remaining populations will NOT breed

  10. allopatric

  11. Sympatric • When a sub-population arises in the midst of the parent population • Many plant species have accidental polyploidy in meiosis. They produce zygotes with multiple sets of chromosomes. • They can no longer reproduce with parental generation.

  12. Evolution of Wheat

  13. What is the tempo of speciation? • Gradual vs. punctuated • Punctuated equilibrium model – species most often diverge in spurts of rapid change instead of slow and gradually. • Over a few to ten thousand years, genetic drift and natural selection can change small, isolated species

  14. Punctuated Equilibrium

  15. Archaeopteryx

  16. Exaptation • Term used to describe a structure that evolves in one context, but becomes adapted for another. However, natural selection cannot anticipate future need Ex. Light bones in reptiles

  17. Evo-Devo • How do evolution and development interface? • Genes control the development of an organism from zygote to adult • Turning these genes on and off at certain times can have a profound effect on development. • Paedomorphosis – the retention of juvenile features as an adult • Ex. axototl

  18. Axototl

  19. Chimpanzee vs. human skulls • We retain a skull more like that of our fetal skull

  20. History of biological diversity • Macroevolution is tied to the history of the Earth • Fossils are recovered from various sources

  21. Sedimentary rocks

  22. Skulls

  23. Petrified trees

  24. Tracks

  25. Body parts

  26. Amber

  27. Geological Time Scale • Four eras – Precambrian, Paleozoic, Mesozoic, Cenozoic • Fossils are dated by carbon dating • Handout • At the end of the paleozoic era (250mya), Pangaea was formed. • The formation of pangaea reduced coastline and changed the environment for many terrestrial species. • Changing ocean currents killed many marine species

  28. Breaking of Pangaea • 180 MYA during the mesozoic • Caused major geographic isolation

  29. Continental drift

  30. Patterns of Evolution • Divergent evolution – when two isolated population evolve independently (Ex. Brown and polar bears) • Adaptive radiation – rapid evolution of a variety of species from a single ancestor (ex. Darwin’s finches) • Convergent Evolution – when two organisms without a common ancestor occupy the same niche, so they have the same characteristics. (ex. Porpoise and penguin)

  31. Patterns cont. • Parallel Evolution – two related species who have made similar evolutionary changes. Ex. Placental and marsupial wolf • Co-evolution – predator/prey relationships

  32. Adaptive Radiation

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