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Chapter 5

Chapter 5. Evolution and Community Ecology. Section 1 - Evolution. Think About It. Just a handful of backyard soil may contain an entire miniature world of life. Insects Mites Millipede Worms Plant Seeds Fungi Bacteria Antarctic ice contains living microbes!

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Chapter 5

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  1. Chapter 5 Evolution and Community Ecology

  2. Section 1 - Evolution

  3. Think About It Just a handful of backyard soil may contain an entire miniature world of life. Insects Mites Millipede Worms Plant Seeds Fungi Bacteria Antarctic ice contains living microbes! How did life come to be everywhere?

  4. Evolution and Natural Selection • Evolution: change over time • Biological Evolution: a change in a population’s gene pool over time • Gene Pool: all of the genes present in a population • Gene: a sequence of DNA that codes for a particular trait • For Example: Mouse Population • Today: 40% Brown – 60% Tan • Next Generation: 28% Brown – 72% Tan

  5. Mechanisms of Biological Evolution

  6. Conditions of Natural Selection

  7. Artificial Selection • Artificial Selection: a human-controlled process to produce individuals with certain traits • Dogs – “like” breeds with “like” = pureblood, “like” breeds with “non-like” = mutt • Agriculture – to make larger, more successful reproducing, diverse plants

  8. Speciation and Extinction • Scientists estimate that all of the species on Earth today represent only a fraction of those that have ever lived. • Speciation: the process by which new species are generated • Allopatric Speciation: speciation due to geographic separation

  9. Allopatric Speciation Glacial Ice Sheets Move – then Recede Major Rivers Change Course – then Return Dry Climate Subdivides Lakes – then Refills Black Kaibab Squirrel and Gray Abert’s Squirrel

  10. Extinction • Extinction: the disappearance of a species from Earth • Scientists Estimate: • 99% of all species that ever lived are now gone • Average time a species spends on Earth is 1 million to 10 million years a# of Species on Earth = (# added by Speciation) – (# removed by Extinction)

  11. Extinction • Background Extinction Rate: the rate at which a gradual, one-species-at-a-time, extinction occurs • Most Extinction • Environmental Conditions change Rapidly • Natural Selection is too slow to adapt • Mass Extinctions: five events that killed off huge numbers of species at once • Best Known = 65 million years ago, wiped out the dinosaurs

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