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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

Chapter 5

Evolution and Community Ecology

think about it
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?

evolution and natural selection
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
artificial selection
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
speciation and extinction
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
allopatric speciation
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

extinction
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)

extinction1
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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