Origins Of Biological Diversity

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Origins Of Biological Diversity

• Chapter 15

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Species

• A population or group of populations whose
  members have the ability to breed with one
  another and produce fertile offspring

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Macroevolution

• Dramatic biological changes that include the
  origin of different species

Diversity Increases
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Speciation

• The formation of new species
• For new species to form there must be a barrier
  between the same species to make the group
  genetically isolated.

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Speciation
Kaibab squirrel Abert squirrel
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Genetic Isolation

• Reproductive Barriers
• Geographic barriers

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Reproductive Barriers

• Prevents closely related species from
  interbreeding
• Timing
• Behavior
• Habitat

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Timing

• Similar species have different breeding seasons
• Eastern Spotted Western Spotted
• Skunk Skunk

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Behavior

• Similar species may have different courtship or
  mating behaviors.
• Ex Eastern Western meadowlarks ?almost
  identical in color shape habitat, but
  difference in courtship rituals differ? different
  species

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Habitat

• Species remain reproductively isolated because
  they are adapted to different habitats.
• Ex Stickleback fish? one is a bottom feeder, one
  spends time in the top open layers of lakes in
  British Columbia, Canada

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Geographic barriers

• A physical barrier that separates a population
  into groups.
• Can be
• Mountains
• Islands with water in between? Darwins 13
  finches on Galapagos
• Valleys? caused by lava flow

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Mountains
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Geographical isolation
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Patterns of Evolution

• Divergent Evolution
• Convergent

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Divergent Evolution

• Related organisms become less alike through
  Adaptive Radiation
• Ex Galapagos Finches? common ancestor on the
  main land? blown to different islands? naturally
  selected into a new species

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Darwins Finches
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Convergent Evolution

• Unrelated species resemble each other due to
  adaptation to similar environments
• Environment has an important selective effect on
  the evolution of species

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A Hummingbird Moth
A Humming Bird
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Rate of Evolution

• Evolution occurs very slowly
• Gradualism
• Punctuated Equilibrium

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Gradualism

• Gradual changes in species over time
• Evidence of many intermediate forms in fossil
  records

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Punctuated Equilibrium

• Scientists found remains of intermediate forms
  but also saw that populations remained the same
  over large periods of time then suddenly changed