Evolution

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Evolution

• Why is it taught?

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Do you agree

• Is there variation within a species?
• Can new variations arise?
• Are there species on earth now that were not here
  long ago?
• Are there species there were here long ago that
  are not here now?
• Can a variation decrease survival chances?

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Do you agree?

• Can a variation increase survival chances?
• Are surviving individuals possibly more
  successful at reproducing healthy offspring?
• Can allele frequencies change in a population?

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Evolution

• If you have agreed with the past eight
  statements, you agree that evolution occurs.
• Now lets take a look

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Why on Earth would anyone think of this kind of
theory?

• Curiosity
• We share Earth with so many millions of other
  kinds of life.
• Human tendency (built into our wiring) to
  categorize or classify
• Consistent similarities in living things that are
  clearly different as well
• Darwin was intrigued with the diversity of life
  which clearly conflicted with popular theory
  about life on Earth.

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How does a hypothesis become a theory?

• Remember a hypothesis must be testable for
  support as well as being refuted.
• If the hypothesis continues to be supported with
  more scientists testing with modern and numerous
  observations and experiments, the hypothesis is
  seen as a theory of science.
• Isn't Evolution Just a Theory?

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II. A. Who was Charles Darwin?

• Strong desire to understand and explain what he
  could observe in nature.
• Naturally curious true scientist
• Naturalist main interests were studying nature
  and collecting a diversity of organisms.
• Recommended for position of naturalist on ship
  called the H.M.S. Beagle. By his professor at
  Cambridge.
• Reluctant rebel

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Darwins Observations

• Most important observations were on the Galapagos
  Islands off the coast of Ecuador.
• Saw similarities and differences among the
  organisms on mainland and the islands (600 mi.
  offshore).
• Became curious about origin of different plants
  and animals and variations of species he recorded
  of similar organisms.
• Finches and tortoises most often talked about in
  books, but he observed other animals and plants
  as well.

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Darwins observations

• Impressed with how organisms survived and
  produced offspring
• Realized importance of ancient organisms in
  solving puzzle of diversity collected fossils.
• Noticed how well suited the species seemed to be
  for their environments.

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Darwins Analysis and Conclusions

• While on journey home he started making careful
  study of the specimens he collected, and thinking
  about the patterns he was seeing.
• When he got back to Britain, he took 20 years to
  carefully develop his theory of evolution.
• Published On the Origin of Species in 1859.

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III. Historical Look at the Theory of Evolution
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Influence on Darwin

• Maybe as Earth changes, so do forms of life.
• It would have to take a long time for life to
  change in the way he was inferring.
• Evolution became a revolutionary idea that was
  inspired by these other controversial
  thinkers.
• Many people found his ideas too shocking to
  accept, and so did he.

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Lamarck (1809)

• Theory of acquired traits (transmutation)
• Need If an organism needs a trait it will get
  the trait through extension of body.
• Use and Disuse If an organism uses a trait it
  will remain otherwise it disappears
• Inheriting acquired traits Traits that the
  parents develop during their life will be passed
  to the children
• Not reasonable in todays world

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Lamarcks Evolution TheoryAcquired Traits
Section 15-2
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Thomas Malthus (1798)

• Before the writings of Lamarck
• The Principles of Population essay stated
  populations outgrew their food supplies.
• This caused organisms to compete and struggle for
  one species to survive against another.
• Predicted humans would also outgrow their food
  supply and space on Earth.
• Note Darwin read this essay.

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Alfred Russel Wallace

• Darwin was reluctant to publish his ideas due to
  the controversial nature of what he was thinking.
• Alfred Russel Wallace was a fellow naturalist who
  sent Darwin an essay on his own findings and
  theories about competition for resources (rings
  of Malthus) which were very similar to Darwins.
• This was the final push he needed to publish his
  own findings.

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What was Darwin thinking?

• He was always interested in using observations
  and prior knowledge (based on reading works of
  others) to formulate his inferences.
• He was not by nature a rebel and trouble maker.
• He was surprised and disturbed by his own
  observations
• He was not going to publish his work, but did
  want others to know of his findings.

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Beliefs of the time

• Not many people accepted the ideas of
  transmutation (evolution) stated by people like
  Lamarck.
• People believed in an Earth and life that were
  only thousands of years old.
• Everyone accepted the Earth and all life were as
  they were when created in one original creation
  event no changes since then.
• When fossils kept popping up, some adjusted their
  beliefs to catastrophic events followed by
  periods of creation.

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Darwins argument

• People were really already using the idea of
  differences in individuals with selective
  breeding.
• Noted that breeders routinely used variation to
  improve crops and livestock, choosing individuals
  with desired traits to breed.
• Darwins term for this artificial selection

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Evolution

• Darwin Theory of Natural Selection
• All organisms produce more offspring than can
  survive
• So, members of the species compete for food,
  space and survival (limited resources).
• Within any population there is variation among
  the members
• Organisms with the best variations for the
  environment in which they live will survive
• Nature selects which organisms will survive
• How Does Evolution Really Work

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Evolution / the controversial parts(descent
with modifications)

• Species change over time.
• Species today have descended with modifications
  from species in the past.
• There is a single tree of life.

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Concept Map
Section 15-3
Evidence of Evolution
includes
which is composed of
which indicates
which implies
which implies
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Evidence for EvolutionEvolution Change in
species over time

• Fossils found in sedimentary rock / fossil
  record
• Geographic Distribution different animals on
  different continents, but similar animals in
  similar environments
• Homologous parts similar in basic internal
  structure but different form and function
• Analogous parts different body structure
  similar in function usually in same environment

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Figure 1514 Geographic Distribution of Living
Species
Section 15-3
Beaver
Beaver Muskrat Beaver andMuskrat Coypu
Capybara Coypu andCapybara
NORTH AMERICA
Muskrat
Capybara
SOUTH AMERICA
Coypu
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Figure 1515 Homologous Body Structures
Section 15-3
Turtle
Alligator
Bird
Mammals
Typical primitive fish
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Evidence (contd.)

• Vestigial organs body structure reduced in
  function (next slide)
• Embryology similar structures in embryos
  develop in same order
• Genetic comparison similar DNA and biochemistry

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Mechanisms for Evolution

• Populations evolve not single organism
• Populations change
• Genetic equilibrium frequency of alleles does
  change from generation to generation
• Genetic drift alteration of allelic frequencies
  by chance
• Geographic isolation populations are isolated
  from other areas island, mountains
• Reproductive isolation formerly interbreeding
  organisms cannot produce fertile offspring

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Evolution of whale from land dwelling mammal.