Evolution

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Evolution
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Charles Darwin

• Was a British Naturalist (a person who studies
  the natural world).
• He came up with theory of Evolution by Natural
  Selection while on an observation trip aboard the
  HMS Beagle.

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The Beagles Journey

• Visited South America and the Galapagos Islands
  (among other places) (1835)
• Darwin saw many plants and animals on the
  Galapagos Islands that were similar to ones found
  in South America, but not the same

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The Galapagos Islands
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Darwins Observations
Turn and talk to your group. What observations
can you make about this Iguana found on the
mainland of South America?
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Darwins Observations

• Mainland
• Iguanas with small claws to climb trees
• Iguanas green in color to blend in with leaves
• Iguanas dont have webbed feet

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Darwins Observations
Now, turn and talk to your group again. What
observations can you make about this Iguana found
on the Galapagos Islands? How does it compare to
the South American Iguana?
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Darwins Observations

• Galapagos
• Iguana's with large claws to grip rocks
• Iguanas gray in color to blend in with rocks
• Iguanas have partially webbed feet

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Why the difference?

• Based on Darwins observations, he theorized that
  a small number of different plant and animal
  species came to the Galapagos Islands from the
  mainland (South America).
• They started reproducing and eventually their
  offspring became different from their mainland
  relatives.

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Darwins Hypothesis

• On his journey home, thought about his
  observations
• Darwins Hypothesis-separate new species may have
  come from one original ancestor

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Darwins Theory of Evolution

• Darwin thought that the species gradually changed
  over many generations and became better adapted
  to the new conditions.
• Species-a group of similar organisms that can
  mate with each other and produce fertile
  offspring
• Evolution-the gradual change in a species over
  time

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What is the difference between a theory and a law?

• A theory is a scientific explanation of an
  observation. Unlike laws, theories actually
  explain why things are the way they are.
• A scientific law is a description of an
  observation. Newtons Laws of motion are good
  examples. Those laws describe forces in physics,
  but they do not explain why they are that way.

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Selection

• Natural Selection- process by which individuals
  that are better adapted to their environment are
  more likely to survive and reproduce than other
  members of the same species. Survival of the
  Fittest
• Artificial Selection- humans decide which traits
  in a species are desirable and breed individuals
  with those traits (aka Selective Breeding)

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Evolution by Natural Selection

• Over a long period of time, natural selection can
  lead to evolution. Helpful traits are passed
  down from parents to offspring while unfavorable
  traits are not.
• Over many generations, the species can change to
  better suit their environment.

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Factors that affect Natural Selection

• 1. Variation
• 2. Overproduction
• 3. Competition

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The 3 Factors in Natural Selection

• 1. Variations-differences between individuals of
  the same species. Variations can be passed down
  from parents to offspring. For example, some
  newly hatched turtles can swim faster than other
  turtles. These faster turtles will survive to
  pass their traits on to offspring who will also
  be fast.

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The 3 Factors in Natural Selection

• Some variations allow members of a species to
  survive and reproduce better than others.

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The 3 Factors in Natural Selection

• 2. Overproduction-organisms produce more
  offspring than can survive. There are not enough
  resources for all to survive so only those that
  have traits best suited for survival will live to
  reproduce. Their offspring will inherit those
  traits.

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The 3 Factors in Natural Selection

• 3. Competition-organisms of the same species must
  compete for resources. For example, some might
  not find enough to eat. Those that are successful
  in competition will live reproduce and pass their
  traits to their offspring.

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In Summary

• Some variations make individuals better adapted
  to their environment so when they reproduce,
  their offspring may inherit those traits.
• The offspring will be better suited for the
  environment and continue to pass the traits on.
• After many generations, more members of the
  species may have the helpful trait. In effect,
  the environment has selected organisms with
  helpful traits to be the parents of the next
  generation.

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Evidence of Evolution

• Fossil Record
• DNA
• Homologous Body Structures
• Similarities in Early Development
• Vestigial Organs

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DNA

• Organisms that have close relatives have similar
  DNA
• The more similar the DNA, the more closely
  related the species are
• Scientists have even found ways to get DNA from
  some fossils

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Homologous Body Structures

• Homologous structures-similar structures that are
  inherited from a common ancestor
• When organisms have homologous structures, it
  means they evolved from a common relative
• Analogous structures-similar structures that
  evolved separately, not from a common ancestor.

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B
A
A shows that that sharks and lizards have a
common ancestor who had limbs like they have
now. B shows that even thought the octopus has a
similar kind of limb as sharks and lizards, it is
an analogous structure since the octopus doesnt
share a common ancestor with the shark and lizard.
Limbarm or leg Tetrapodan organism with 4 limbs
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Similarities in Early Development

• Scientists look at early development of different
  organisms to see if they are similar

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Vestigial Organs

• A body part that doesnt seem to have any
  function at this time
• Ex-appendix, tailbone and wisdom teeth in humans,
  pelvic bone in whales, wings on ostrich and emus

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What does it all mean?

• Scientists have combined evidence from fossils,
  DNA, similar structures, etc to determine
  evolutionary relationships among species
• Branching Tree- a diagram that shows how
  scientists think different groups of organisms
  are related

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One Last Thing

• The Evolution of Homer
• http//youtu.be/faRlFsYmkeY