Evolution Part 1

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Evolution Part 1

• The Evidence

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Evolution Outline

• I. What is evolution?
• II. Evidence of Evolution
• A. Evidence from the past (Fossils)
• B. Evidence from living organisms
• -Comparative anatomy
• -Comparative embryology
• -Comparative biochemistry
• III. Early Hypotheses Origin of Life
• A. Spontaneous generation
• B. Atmosphere of early earth Stanley Miller
  experiment
• C. Heterotroph hypothesis

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Evolution Outline (Cont)

• IV. Theories of Evolution
• A. Early Theories
• 1. Lamarck Theory of acquired traits
• Use and disuse
• 2. Darwin and WallaceTheory of evolution by
  natural selection
• B. Synthetic (Modern) Theory of Evolution
• 1. Population Genetics
• 2. Genes, Variation and Evolution
• 3. Hardy-Weinberg Law and Genetic Equilibrium
• V. Adaptations and Natural Selection
• A. Structural Adaptations
• B. Behavioral Adaptations

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Evolution Outline (Cont)

• VI. Types of Natural Selection
• A. Directional Selection
• B. Stabilizing Selection
• C. Disruptive Selection
• VII. Speciation and Adaptive Radiation
• A. Geographic and reproductive isolation
• B. Convergent evolution
• C. Coevolution
• VIII. Classification and Evolutionary Histories
• A. Phylogenetic trees
• B. Taxonomy

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What is evolution?

• Evolution is the central and unifying theme in
  biology.
• Nothing in biology makes sense unless cast in
  the light of evolution Theodozius Dobzhonski
• Evolution is the gradual change in a population
  of organisms over time.
• Geologic evolution Refers to the gradual changes
  in the Earth over the last 4.5 billion years
• Organic evolution refers to the changes in life
  forms as they adapt to their changing
  environments.

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Is evolution real?

• There is no doubt that evolution has occurred, is
  occurring, and will continue to occur as
  organisms constantly adapt to changing
  environments.
• Convincing evidence comes from the fossil record.
• Fossil any trace or remains of an organism that
  has been preserved by natural processes.

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Transitional Fossils Evidence of Evolution Part
1

• Archeaopteryx
• Had teeth and a long tail like a dinosaur, but
  feathers like a bird.
• This fossils demonstrates how birds are modern
  descendents of dinosaours.

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Transitional Fossils

• Tiktaalik 375 million year old fish whose fins
  appear to be limbs in the making
• The figure below shows bones in the fins that are
  homologous to bones that make up the fingers,
  wrists, and elbows of terrestrial (land dwelling)
  vertebrates.

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Transitional fossils

• Evolving from life in the sea to life on land
  required some major limb adjustments
• Tiktaalik is a long awaited piece of the puzzle
  of how life transitioned from sea to land

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Sealing up gaps in the fossil record.

• Opponents of evolution often point to a lack of
  evidence or gaps in the fossil record to
  justify their position.
• but rarely change their positions when
  confronted with the real evidence.

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But surely this evolution stuff doesnt apply to
humans.
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Question to Ponder

• Why arent there more, lots more, transitional
  fossils out there? Most fossils are of organisms
  in their complete state.

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Evidence for Evolution Part 2 Comparative Anatomy

• What traits would you use to classify
• -Birds
• -Mammals
• -Reptiles
• -Fish

• Feathers, lay eggs
• Fur, milk, live young
• Scales, cold-blooded, lay eggs
• Scales, gills, fins

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Comparative Anatomy Homologous Structures

• Homologous Structures are characteristics which
  are shared by related species because they have
  been inherited in some way from a common
  ancestor.
• For example, although the arms of four-limbed
  vertebrates externally appear quite different,
  all have the same basic underlying skeletal and
  muscular pattern. Such shared patterns are best
  explained by the inference that they were
  inherited from a common ancestor that also had
  this pattern.

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Homologous Structures and Wing Development

• The wings of flies, moths and butterflies, and
  beetles are homologous structure derived from a
  four winged common ancestor.

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There is also homology in gene expression

• Similarities in gene expression between mammals
  and insects demonstrate the common ancestry of
  ALL animals.

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Comparative Anatomy Analogous Structures

• Insect wings and bird wings are considered
  Analogous Structures.
• Insect wings and bird wings have evolved
  independently of each other.
• They illustrate two different evolutionary
  pathways to the same result wings.
• This is called convergent evolution
• Analogous structures do not demonstrate common
  ancestry between organisms.

• Would you say that a butterfly is more closely
  related to a bird or an ant?
• But birds and butterflies both have wings.
• True, but the underlying structure of those wings
  are completely different.

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Analogous Structures

• Here we can see why vertebrate forelimbs are
  considered HOMOLOGOUS reflecting the common
  ancestry of all vertebrates.
• And why the wings of insects and birds are
  considered ANALOGOUS reflecting the convergent
  evolution of bird and insect wings.

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Comparative AnatomyVestigial Organs

• Some of the most compelling evidence supporting
  evolution comes from vestigial organs.
• Vestigial organs Structures that were functional
  in early ancestors, but are now useless in
  present day organisms.
• Ex. Hind-limb bones in whales and snakes, human
  appendix and nictitating membranes

• Why does this early whale fossil have
  non-functional leg bones?
• They were used by a land dwelling ancestor
  similar to modern hippos

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Vestigial leg bones found in snake fossil

• This fossil demonstrates the evolution of snakes
  from lizards.
• The loss of limbs enables snakes to exploit new
  areas in search of prey, that would not be
  accessible to lizards.
• The only sensible explanation as to why a snake
  fossil would have functionless leg bones is an
  evolutionary explanation

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Vestigial Eyes in Cave Dwelling Salamanders

• Grotto salamander
• Typhlotriton spelaeus

• This lizard lives in caves with absolutely no
  light.
• Rather than invest precious resources for
  unnecessary eye development, these blind
  creatures have functionless bulbs of tissue
  rather than eyes.

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Evidence for Evolution Part 3 Comparative
Embryology

• Comparative embryology Refers to the
  similarities and differences between organisms
  during embryological development.
• Vertebrate embryos develop in very similar ways.

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Evidence for Evolution Part 4 Biochemical
Similarities
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Comparative Biochemistry

• Just as DNA can be used to demonstrate paternity,
  it can also be used to demonstrate common
  ancestry between species.

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We dont just look like other primates, we share
most of our DNA with them too!
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Evidence for Evolution Part 6 Artificial
Selection

• Artificial Selection and Selective breeding has
  enabled humans to develop a variety of dog,
  horse, livestock, and agricultural breeds.
• Darwin argues that humans are simply playing the
  part of the environment in the selection of
  desired traits.

• All of these vegetables come from the same
  mustard plant!

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Artificial selection in dogs

• All dog breeds (Canis familiaris) are derived
  from domesticated dogs very similar to wolves.
• Artificial selection gives us tremendous
  diversity within the species.