Chapter 15

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Chapter 15 The Theory of Evolution
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What is EVOLUTION?

• A textbook definition of evolution

evolution can be precisely defined as any
change in the frequency of alleles within a gene
pool from one generation to the next." - Helena
Curtis and N. Sue Barnes, Biology, 5th ed. 1989
Worth Publishers, p.974
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What is EVOLUTION?
Put a simpler way

• The change in a species over time.

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I. What evidence is there for Evolution?

• A. Fossil records
• B. Transitional species
• C. Geological time and dating
• D. Anatomical trends
• E. Embryology
• F. Biochemical/Molecular data

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A. Fossil Record

• What is a Fossil?
• Preserved remains, imprints, or traces of an
  organism that has survived.

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i) Types of fossils

• Mold sediment hardens around an organism
  preserving the outside shape.
• Cast sediments enter a mold and harden.

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Fossils (cont.)

• Petrifaction atoms in living tissues are
  replaced by minerals.
• Imprint footprints, tracks, or tunnels made by
  an organism.

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B. Transitional Fossils

• Fossils that show a relationship or evolutionary
  link between two different species of a family of
  organisms.

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Archaeopteryx
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Archaeopteryx

• 1) Reptile features
• Trunk region vertebrae are free.
• In birds the trunk vertebrae are always fused
  together.
• Neck attaches to skull from the rear.
• As in dinosaurs not from below as in birds.

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Archaeopteryx

• 2) Bird features
• Feathers.
• Opposable hallux (big toe).
• Pubis (hip bones) are elongated and directed
  backward.

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Protospinax
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Protospinax

• 1) Ray features
• Flattened body.
• Primitive teeth.
• Spent large amounts of time on the sea and ocean
  floors.

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Protospinax

• 2) Shark Features
• 5 foot long body.
• Had a detached upper jaw.

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Other transitional fossils

• 1) Acanthostega
• 2) Canobius
• 3) Ichthyostega
• 4) Karaurus
• 5) Panaderichthys
• 6) Trematops
• 7) Vieraella

And Many More
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C. Geologic time dating

• The Earth is 4.5 Billion Years Old!

If the Earths history was just one year long
then

• Each day would be about 12 million years!

• First bacteria about the middle of March.

• Dinosaurs dont show up until late November.

• Humans havent even been around a ½ day.

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How do we know the earth is that old?

• By using the technique of radioactive dating of
  different isotopes!
• (Example Carbon dating)

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Other radioactive isotopes
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D. Anatomical Trends

• 1. Homologous structures structures with the
  same general form and originating from the same
  region of the embryo.
• 2. Vestigial structures a structure that has
  been greatly reduced with no apparent function.
  (thought to at one time have a purpose)

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1. Homologous structures
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2. Vestigial structures

• Examples
• a. Whales have a pelvis yet no feet.
• b. Cave salamanders have eyes although they are
  blind.
• c. Humans have a tailbone but no tail.

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E. Embryological development

• Embryos of certain species develop almost
  identically especially in early stages.
• The embryos of all vertebrates (animals with
  backbones) have gill slits and a tails, which
  indicates that all vertebrates may have common
  ancestry.

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F. Biochemical/Molecular

• 1) DNA and RNA are made of the same nucleotides
  in ALL organisms.
• 2) ATP is the energy molecule of all life
  systems.

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Biochemical/Molecular

• 3) The metabolism of different organisms is based
  on the same complex biochemical compounds.
• 4) Certain blood proteins are found in almost
  every organisms.
• 5) The protein (cytochrome c) is essential for
  all organisms that perform aerobic respiration.

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II. Developing the Theory of Evolution

• The Theory of Evolution is a carefully reasoned
  and tested hypothesis about how evolutionary
  change occurs.

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Theories of Evolution

• A. Jean Baptiste de Lamarck (1809)
• His theory was eventually disproved but it was
  the first attempt to support evolution.

B. Charles Darwin Alfred Wallace (1858)
Came up with an almost identical theory on
evolution although each worked separately.
(Basis for our current theory of evolution.)
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A. Theory of Acquired Characteristics(Lamarck)

• Also known as Theory of Use and Disuse
• Organisms acquired traits during their lifetime
  and then passed those traits to their offspring.

Example If giraffes stretched their necks to
reach leaves higher on the trees, then their
offspring would have longer necks.
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Lamarck vs. Darwin

• Darwin said
• Giraffes with long necks survived and those with
  short necks died because they had to compete for
  food that was higher up in trees.
• Consequently, the long neck genes were passed on
  and over time the average giraffe had a longer
  neck.

• Lamarck said
• Giraffes STRETCHED their short necks to reach
  food.
• Consequently, they then passed on the stretched
  (acquired) long-necks to their offspring.

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B. Charles Darwin

• Charles Darwin was born on February 12, 1809 in
  Shrewsbury, England.
• Contrary to popular belief, Darwin was not the
  first person to describe the concept of
  evolution, but he was the one who gave it its
  popularity.

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Charles Darwin

• Darwin set sail on the H.M.S. Beagle (1831-1836)
  to survey the south seas (mainly South America
  and the Galapagos Islands) to collect plants and
  animals.
• On the Galapagos Islands, Darwin observed species
  that lived no where else in the world.
• These observations led Darwin to write a book in
  1859 called The Origin of the Species by Means
  of Natural Selection.

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Galapagos Islands
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Galapagos Islands Darwins Finches
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Darwins Finches

• 1. All of the finches came from the same 2 parent
  finches.
• 2. The birds reproduced and some of their
  offspring flew to different islands.
• 3. Each population adapted to their unique
  environment.
• 4. Finches prefer not to fly long distances.
  Thus, reproductive isolation occurred.
• 5. Birds that lived on the same island evolved in
  their own unique ways leading to formation of new
  species of finch.

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Darwins Finches

• There are 13 different species of finches on the
  Galapagos Islands all evolved from a single
  ancestor.

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Each species of finch live on a different island
and they have adapted to that particular
environment.
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Consequently, each species has developed their
own set of behavioral and physical differences.

• Example
• The Galapagos finches
• can vary greatly. Some
• eat small seeds while
• others prefer large seeds,
• and some eat ticks all
• because of differences in
• their beaks.

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III. Natural Selection

• Darwin knew nothing of genes, but what he did
  have were many observations and a little
  foresight that provided the driving force for
  evolution.

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Darwins Field Observations

• 1. Organisms produce more offspring than can
  survive which creates competition.

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Darwins Field Observations

• 2. Not all members of a species are exactly alike.

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Darwins Field Observations

• 3. The members with the most favorable traits to
  their environment will survive (survivial of the
  fittest).
• 4. Survivors with the favorable traits will pass
  them on to their offspring.

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Darwins Field Observations

• 5. In time, the most favorable traits may become
  adaptations for the survival of that species.
• 6. If the new species is different enough from
  its ancestors we say a new species is created

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Modern Theory of Evolution

• Same as what Charles Darwin and Alfred Wallace
  described, AND adding the new information that
• Mutations are a way of producing changes in
  members of a species.

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Modern Theory of Evolution

• Population isolation leads to the formation of
  new species because they become so different from
  one another that they cannot interbreed.

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Modern Theory of Evolution

• Mass and minor extinctions lead to the
  replacement of that species by other species that
  are better suited to the environment.

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General rules about Evolution

• When facing a constantly changing environment a
  species must get M.A.D.
• (Migrate, Adapt, or Die)

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IV. Types of Evolution

• Evolution is not unidirectional. Some species
  grow less alike, some grow more alike, and some
  change in response to changes in others. These
  are the Patterns in Evolution.

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A. Divergent Evolution

• The process where two or more related species
  become more and more dissimilar.
• Example
• 1. The color of the Red Fox helps it blend in
  with the trees in its environment while sandy
  color of the Kit Fox helps it blend into the
  desert.

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B. Convergent Evolution

• Species from different evolutionary branches may
  come to resemble one another if they live in very
  similar environments.
• Example
• 1. The Ostrich (Africa) and Emu (Australia) look
  alike due to the similar environments in which
  they live.

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C. Coevolution

• Evolutionary change, in which one species act as
  a selective force on a second species, inducing
  adaptations that in turn act as a selective force
  on the first species.
• Example
• 1. Humming Birds have a beak relative to the
  length of the plants with flowers that have
  longer or shorter tubes.

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Any Questions?

• It is the mark of an educated mind to be able to
  entertain a thought without accepting it.
  Aristotle
• It is not the strongest of the species that
  survives, nor the most intelligent, but the most
  responsive to change. Darwin