Natural Selection

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Natural Selection
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Todays Objectives SOL BIO.8b-d

• TSW investigate and understand how populations
  change through time, including
• How variation of traits, reproductive strategies,
  and environmental pressures impact on the
  survival of populations
• Recognizing how adaptations lead to natural
  selection
• How new species emerge

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Charles Darwin

• On the Origin of Species
• Sailed with the HMS Beagle
• Observations made in the Galapogos Islands
• These observations helped him form the theory of
  how species change over time called natural
  selection

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What is Natural Selection?

• Natural selection is governed by the principles
  of genetics.

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Types of Adaptations

• Protective Coloring
• Camouflage
• Mimicry
• Physiological Adaptations
• Reproductive Changes
• Other changes
• Behavioral Adaptations

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Evidence for Evolution

• Fossil record
• Anatomy
• Homologous structures
• Analagous structures
• Vestigial structures
• Embryology
• Molecular biology (DNA differences)

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What is a Population?

• Populations evolve over many generations,
  individuals dont
• Populations are groups of interbreeding
  individuals that live in the same place at the
  same time
• Individuals in a population compete for resources
  with each other

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How Does Evolution Work?

• Populations produce more offspring than the
  environment can support
• The unequal ability of individuals to survive and
  reproduc leads to the gradual change in a
  population over many generations

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Mechanism for change in a population of organisms

• Animals who have greater fitness survive in
  environment and live to reproduce
• Random changes (mutations) can lead to greater or
  less fitness
• Adaptations allow an organism to survive better
  in their environment

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Mutations Variety Produced by Sexual
Reproduction Allow for Diversity within a
Population

• Genetic drift (caused by chance)
• Bottleneck
• Founder effect
• Genetic equilibrium
• Hardy-Weinberg law
• In H-W equilibrium, does not occur

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Adaptations

• Can arise in response to environmental pressures
• Temperature
• Antibiotic resistance in bacteria
• Pesticide resistance
• Morphological changes in peppered moths

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Types of Selection

• Directional
• Extreme form favored by natural selection
• Stabilizing
• Middle form most successful
• Disruptive
• Two extreme forms successful in separate
  environments

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How are new species created?

• Geographic isolation
• Reproductive barriers
• Change in chromosome numbers
• Adaptive radiation

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Types of Evolution

• Convergent evolution
• Dolphins fishes
• Wings of bees bats
• Divergent evolution
• Darwins finches
• Adaptive radiation

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How fast does evolution occur?

• Gradualism
• Darwin
• Species change slowly over time
• Punctuated Equilibrium
• Gould Lewontin
• Species can make rapid leaps in evolution
• Modern Synthesis
• Parts of both are correct