Evidence for Evolution

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Evidence for Evolution
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Intermediate Species The horse

• An Intermediate Species is a species that shows
  the link between ancient fossils and modern
  species to show how an animal evolved.
• An example of this is the horse. These pictures
  are from the Natural History Museum near USC.

• Notice how the horse gradually becomes larger.
  You cannot see it in these pictures, but the hoof
  changes from 3 toes to 2.

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Vestigial Structures

• Vestigial Structures are things that have no
  current use to an organism. They show evolution
  because before the organism changed they were
  useful.
• Examples in humans are appendix, hair on the
  body, wisdom teeth, tail bone, nipples on males,
  muscles to move ears.

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Homologous Structures
Human
Cat

• Homologous structures are structures that do very
  different things, but have the same basic
  structure
• Example wing of a bat, arm of a human, flipper
  of a whale, leg of a cat.

Whale
Bat
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Analogous Structures

• Analogous structures are structures that have the
  same function (do the same thing) but are made
  completely differently.
• Example Hummingbird Moth (an insect) and
  Hummingbird (a bird)

Hummingbird Moth
Hummingbird
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Similarities in Embryology

• A guy named Haeckel looked at embryos (unborn
  organisms), and thought that they looked very
  similar. So he changed his drawings to make them
  look more similar (falsifying data a big no-no in
  science). However, his pictures stayed around and
  are still in some textbooks today.
• He used this to propse that as higher organisms
  developed they passed through stages of lower
  organisms.
• This idea is completely wrong. There is no such
  thing as a higher organism.
• However, embryos for very different organisms are
  very similar at an early stage and this helps
  show that organisms are related and is evidence
  for evolution, even though Haeckles drawings
  were fakes.

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Embryology Cont.
Comparison of Haeckle and Actual Photos
Haeckles Forgeries
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Similarities in Macromolecules

• Remember that Macromolecules are the basic
  building blocks of all living things (are cells
  are made of macromolecules) Proteins, Lipids,
  Carbohydrates, Nucleic Acids.
• It is striking that all life has the same genetic
  code and uses the same molecule (DNA) with the
  same nucleotides.
• Moreover, more similar organisms (organisms with
  recent common ancestors) have more similar
  macromolecules than organisms with remote
  ancestors.
• This is so universal among life that we classify
  organisms (K,P,C,O,F,G,S) based on how similar
  their RNA and Proteins are. Usually when
  physical characteristics and RNA and Proteins are
  compared they show the same relationships.

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Moths in Hawaii

• The banana was brought to Hawaii 1000 years ago
  by Polynesians.
• We can assume that nothing was adapted to
  fertilize the banana when Polynesians first
  arrived.
• Today there are 7 species of moths that only feed
  on the banana flower.
• These moths must have adapted within the last
  1000 years since the introduction of the banana.
• This is also evidence that evolution sometimes
  can occur very quickly when there is an
  environmental change.

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Evidence for Natural Selection The Peppered Moth

• The previous examples were all for evolution
  the changing and creation of new species. The
  following example is for natural selection
  changing the frequency of an allele in a
  population.
• The peppered moth is a moth found in England. It
  lives in the forest, and looks like an ordinary
  moth.

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Peppered Moth Cont.

• Normally peppered moths were white, which makes
  them camouflaged on white birch trees.
• Some peppered moths were black (10). They were
  easy to see on white trees and get eaten more
  often by birds.

Can you find the white moth?
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Peppered Moth Cont.

• During the Industrial Revolution, London began to
  pollute in huge quantities. Because they burned
  only coal, eventually soot and black lichen began
  to cover the trees. This turned most trees
  black.
• During this time the black peppered moths had an
  advantage, and their numbers increased so that
  most peppered moths were black, not white anymore.

Can you find the black moth?
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Peppered Moth cont.

• Eventually England passed clean air laws. This
  cleaned up the forest, so that most trees became
  white again.
• Because of this white moths gained an advantage
  again.
• Today most peppered moths are white.
• Why didnt the black allele disappear? Think of
  your lab did the albino allele (g) disappear?

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Extra Credit

• The story of the peppered moth is based on
  research by Kettlewell, 1959, done in a lab.
• It seems that the story of the peppered moth is
  much more complex that first thought..
• Research the peppered moth at http//www.praxagora
  .com/stevet/netfuture/ni/misc/pub/moth.html and
  write a 1 page summary of the full story of the
  peppered moth.