Evolution by Natural Selection

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Evolution by Natural Selection

• Adapter from Mrs. Knox

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Charles Darwin

• Father of Evolutionary Theory
• H.M.S. Beagles Naturalist
• Studied anatomy of
• biological specimens
• formulated the Theory of Natural Selection.

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Survival of the Fittest

• Natural Selection individuals best suited to
  their environment
• survive better
• reproduce better
• pass on their genes better
• Depends on variation existing in populations.
• Variation differences in appearance within the
  same species.
• examples hair color, feather color beak size
• Nature selects for favorable traits and against
  those without them.

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Normal Curve

• Natural variation in populations is the raw
  material for evolution
• Natural variation comes from genes

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Adaptations

• Adaptations a trait which helps a species
  survive.
• Adaptations may take millions of years or may
  occur rapidly.

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• Peppered moth populations have evolved to a
  darker form
• trees become darker because of pollution
• dark moths in existence gained camouflage
• Survived better reproduced better than light
  moths

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Types of Adaptations

• Structural
• Changes in a body
• Mimicry camouflage
• Physiological
• Changes in metabolic processes
• Pesticide resistance in insects
• Behavioral
• Changes in behavior
• Social behavior in wolves or primates

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3 Types of Natural Selection

• Stabilizing Selection selects for average
  individuals and against extremes
• Large spiders are easily seen captured
• Small spiders cant catch enough prey
• Medium spiders dont attract predators are
  large enough to be effective predators

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3 Types of Natural Selection

• Directional Selection selects for one extreme.
• Deep burrowing insects invade woodpecker habitat
• Those woodpeckers with longer beaks eat better,
  survive better reproduce better

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3 Types of Natural Selection

• Disruptive Selection both extremes are selected
  for.
• Rocks in flounder environment are both light and
  dark
• White and brown flounder can blend in but tan
  flounder cant
• Tan flounder are selected against

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Speciation

• Natural Selection leads to the development of new
  species
• Species group of organisms that look alike and
  have the ability to
• interbreed
• have fertile offspring

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Cause of Speciation

• Geographic Isolation physical barrier separates
  population into 2 parts.
• Breeding between 2 populations stops
• Over many generations populations change into new
  species
• Examples clear cutting, sea levels changes,
  volcanic eruptions

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Causes of Speciation

• Reproductive Isolation formerly interbreeding
  populations are prevented from creating fertile
  offspring
• Example fall and spring breeding seasons

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Speed of Speciation

• Gradualism speciation occurs at slow steady rate
  with small adaptive changes gradually accumulate
• Punctuated Equilibrium speciation occurs in
  rapid bursts with long periods of stability in
  between.
• environmental conditions change
• introduction of new competitive species

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Patterns of Evolution

• Adaptive Radiation ancestral species separate
  into many species which occupy different niches.

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Patterns of Evolution

• Divergent evolution species have become more and
  more different.
• Homologous structures same structure from common
  ancestor, different function

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Patterns of Evolution

• Convergent Evolution distantly related organisms
  evolve same traits.
• Analogous structures different structure, same
  function.
• fins streamline body for aquatic predators

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Evidence for Evolution

• Fossils evidence in sedimentary rock of an
  organism that lived long ago.
• Amber
• Casts
• trace fossils
• Imprints
• Molds
• petrified wood

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How do we find the age of a fossil?

• Relative dating layers of rock closer to the
  surface are younger than deeper rock, so
  placement of the fossil in those layers gives an
  estimate of its age.

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How do we find the age of a fossil?

• Radiometric dating using the amount of
  radioactive isotopes left in the fossil to
  estimate its age.
• Half-life the amount of time it takes for half
  of a specific radioactive isotope to decay.
• Potassium 40 turns into
• Argon 40 over time
• 1/2 life 1.3 billion years
• Carbon-14 5730 years

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• C-14 Dating Procedure

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Evidence for Evolution

• Comparative Anatomy comparing body parts of
  species.
• homologous analogous structures

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Evidence for Evolution

• Comparative Embryology if embryos appear similar
  then there is a common ancestor.

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Evidence for Evolution

• Vestigial structures body part that is reduced
  in function today, but may have been used by
  ancestors.

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Evidence for Evolution

• Genetic Comparisons DNA testing to see how many
  pairs of nucleic acids are similar.
• Most reliable form of evidence.