Ch. 22 Descent with Modification:

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Ch. 22 Descent with Modification

• A Darwinian View of Life

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View of life

• Before Darwin
• Plato
• Two worlds, real (ideal/eternal) and illusory
  (imperfect)
• Evolution counterproductive
• Aristole scala naturae
• No evolution, permanent.
• Natural Theology
• Nonevolving, Creators plan, creators
  purpose/design
• Carolus Linaeus Taxonomy, no evolutionary kinship

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Fossils, Paleontology

• Sedimentary Rocks/fossils, strata, erosion,
  organism succession
• Georges Cuvier catastrophism (Paleontology)
• James Hutton gradualism/mechanisms, current
• Charles Lyell uniformarianism geological
  processes

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Lamarck

• Two Concepts used
• Use/Disuse
• Inheritance of acquired characteristics
• Adaptation to the Environment Primary product of
  evolution
• Sentiments interieurs or felt needs

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Darwinian Revolution (1809-1882)

• University of Edinburgh (medicine)
• Christ College at Cambridge (clergyman)
• Natural theology
• 22 yrs. Old sailed on HMS Beagle
• Chart South American coastline
• Studied plants and animals
• Galapagos
• Returned 1836
• Used Lyell and Lamarck studies

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What was his reasoning?

• The voyage of the Beagle
• Galapagos islands
• Darwin focused on adaptation
• descent with modification
• observations

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Whats the reason for diversity and numerous
similarities among species?

• On the Origin of Species by Means of Natural
  Selection. 1859. Charles Darwin.
• In his book, Charles Darwin made 2 major points
• 1. Species evolve from ancestral species and
  were not specially created.
• 2. Natural selection is the mechanism that could
  result in this evolutionary change.

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• Branching history
• Most branches extinct (99)

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Observation 1

• All species have such great potential fertility
  that their population size would increase
  exponentially if all individuals that were born
  reproduced successfully.

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Observation 2

• Populations tend to remain stable in size, except
  for seasonal fluctuations.

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Observation 3

• Environmental resources are limited.
• Inference 1
• Production of more individuals that the
  environment can support leads to a struggle for
  existence, with only a fraction of offspring
  surviving.

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Observation 4

• Individuals of a population vary extensively in
  their characteristics/ no two individuals are
  exactly alike.

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Observation 5

• Much of this variation is heritable.
• Inference 2
• Survival is not random, but depends in part on
  the hereditary constitution of the surviving
  individuals. Those individuals whose inherited
  characteristics fit them best to their
  environment are likely to leave more offspring
  than less fit individuals.
• Inference 3
• This unequal ability to survive and reproduce
  will lead to a gradual change in a population.

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Summary of Darwins Ideas

• Natural selection differential success in
  reproduction.
• Natural selection occurs from the interaction
  between the environment and the inherent
  variability in a population.
• Variations in a population arise by chance, but
  natural selection is not a chance phenomenon.
• Artificial Selection breeding of plants and
  animals.

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Example of Natural Selection

• Ground Finches
• avg. beak depth (inherited trait) oscillates with
  rainfall.
• Wet years - feed on small seeds - avg. beak depth
  decreases.
• Dry years - small seeds less plentiful, survival
  depends on the finches being able to crack the
  less preferred larger seeds. Avg. beak depth
  increases.
• What does this study indicate?

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What does this study indicate?

• Natural selection is situational. What works in
  one environment may not work in another.
• The environment did not create beaks specialized
  for large or small seeds, but only acted on
  inherited variations already present in the
  population.

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Current evidence of Natural Selection
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Figure 22.13 Evolution of drug resistance in HIV
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Evidence for Evolution

• Homology
• Anatomical
• Vestigial
• Embryonic
• Molecular
• Biogeography
• endemic
• Fossil record
• Drosophila fossils in Hawaii

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Theoretical about Evolution???
Theories are attempts to explain facts and
integrate them with overreaching concepts.
Natural Selection is the proposed mechanism of
Darwins Theory of Evolution
Theories are more than a simple
hypothesis. Predictions stand up with continuous
testing by experiments and observations
There is grandeur in this view of life