Evidence for Evolution

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Evidence for Evolution

• Stations 1-6

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Organisms from station 1

• A. Human
• B. Horse
• C. Bat
• D. Whale
• E. Mole
• F. Cat
• G. Bird
• H. Kangaroo
• I. Monkey

If you had any of the organisms listed
incorrectly, write the correct organism next to
your previous answer. As there are no wrong
answers for this portion of our lab, you dont
have to erase incorrect responses. It is
sufficient to place the correct answer next to
the ones you may have guessed wrong.
3
Which characteristics do these animals share?
Which characteristics differ?

• They all have similar bone structure.
• They differ in the relative size and shapes of
  the bones.

4
What do you think might account for the
differences you observed?

• Modifications in size and shape of bones are
  called
• ADAPTATIONS

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Adaptation

• Physiological and/or behavioral adjustments made
  by organisms in response to environmental
  circumstances. Adaptations may be short-term or
  long-term, and strictly defined, they are the
  results of evolutionary factors.
• Basically a trait that increases an organisms
  survival and reproduction
• Forelimb bones in humans, whales, bats, etc. are
  structurally similar, but have been modified.
• Common evolutionary origin explains similarities
  in bone structure (ex. Bones in bat wing and
  whale flipper)
• Comparative Anatomy is a major source of evidence
  for evolution.

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Station 2

• Variation in domestic dogs.

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Variation in domestic dogs.

• How many species are represented in the photos?
• - ONE! Species (different breeds)
• - Different breeds CAN mate and produce
  offspring,
• different species cannot.
• What is the relationship between the dogs job
  and major morphological differences (size, shape,
  etc.)?
• - Different shapes and sizes accommodate the
  kind of job the dog has.
• For Example Dachshunds route badgers out of
  holes. Its paws are suited for digging, and its
  short, long, thin body allows it to move into the
  badger holes. A Great Dane would not make a very
  good badger hunter!

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Species

• A set of potentially interbreeding organisms.
• Cannot mate with different species and produce
  offspring capable of reproduction.
• (Ex. HorseDonkeyMule) -gtcant reproduce

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Artificial Selection

• Humans choose what is adaptive dogs with
  particular traits selected for breeding.
• Other examples include
• - Milk production in cows.
• - Shorter fruit trees (picker friendly)
• - GMOs (genetically modified objects)

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Station 3 Similarity can be tricky.
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What traits do the organisms share? What is the
function of the shared traits? Are they close
relatives?

• Set-Up A
• fur color
• ---gt protection
• ---gt camouflage
• Close relatives?
• - Mammals, BUT do NOT share a recent common
  ancestor

• Set-Up B
• presence of a wing
• ---gt allows the animal to fly or glide
• Close relatives?
• - NO. Group includes both vertebrates AND
  invertebrates.

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Trait similarity is not always a good indicator
of evolutionary relationships.

• CONvergent Evolution
• Organisms that evolve under similar
  environmental pressures may evolve similar forms.
  (Ex. White fur in white habitats.)
• Divergent Evolution
• New species form through gradual changes in
  traits over time due to different environmental
  pressures.

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Example of Divergent Evolution

• Brown bears and polar bears.
• Brown bears and polar bears are close relatives.
• Glaciers isolated a population of brown bears
  100,000-250,000 years ago.
• Bears with lighter coats better predators in
  snowy habitat.
• Lighter coats therefore increased chance of
  survival and reproduction.

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Station 4

• Evolution isnt like Burger King
• You cant have it your way

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Shared characteristics among these organisms

• Wings, webbed feet, feathers, warm-blooded.
• Why?
• - Live near water? To help them swim?
• Which birds DO NOT go in the water?
• - Frigate bird, Arctic Tern

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• Frigate Bird
• - No waterproof feathers, harasses other
  seabirds and then steals the fish they drop!
• Arctic Tern
• - Doesnt swim well, swoop down to grab fish and
  keep flying to stay out of water flies about
  20,000 roundtrip to migrate

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Key Ideas

• Evolution does not happen because an organism
  NEEDS a particular trait.
• Evolution doesnt necessarily work towards
  creating a perfect organism.
• Think If organisms could evolve a trait when
  they needed it, why would so many organisms have
  gone extinct?

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Station 5

• The tree of life.

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Key Ideas

• Origin of life on Earth is about 3.5 billion
  years ago.
• Evolution is not a ladder of upward progress with
  humans on the top rung.
• Evolutionary history better represented as bush
  or tree with BRANCHING
• All living things derive from a common ancestor.

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Over time evolutionary branch may

• Not change (ex. turtles, horseshoe crabs)
• Go extinct (ex. dinosaurs)
• Diverge into two different organisms
  (ex. polar bears and brown bears)

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Station 6

• How do genes inform us about evolution?

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Genetic similarity between pairs based on a
single gene.
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• Which pairs of organisms are the most closely
  related?
• - Human-Chimp and Horse-Donkey
• Which organisms are the most and least closely
  related to humans?
• - Most chimp (or mouse)
• - Least corn (or fish)

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Key Ideas

• Genetic similarity indicates evolutionary
  relationships
• This is another important source of evidence for
  evolution.
• Genetic evidence generally supports HYPOTHESES
  generated using comparative anatomy or fossil
  data
• Evolutionary hypotheses are modified as new
  evidence is generated from
• - Comparative Anatomy
• - Fossil Data
• - Patterns of embryonic development
• - Genetic Data

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