What is the Evidence for Evolution?

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What is the Evidence for Evolution?

• Chapter 15

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Quiz 3

• What gas could not have been present in the early
  atmosphere if organic compounds were synthesized
  naturally?
• Name one of the three scientists who did
  experiments suggesting that spontaneous
  generation was false.
• Were the first cells believed to be heterotrophs
  or autotrophs?

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Quiz 3 Continued

• Who wrote, The Origin of Species?
• Who is the father of modern taxonomy?

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Overview

• Introduction to Evolutionary Theory
• Brief History of Western Ideas on Evolution
• Various Evidences for Evolution
• The Mechanism of Evolution

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Defining Evolution

• Darwin- descent with modification
• heritable change in populations over time
• adaptive change- a genetic change that increases
  an organisms chances of perpetuating its genes
  in future generations
• Microevolution- changes in the frequences of
  alleles of genes in a population
• Macroevolution- the process by which species and
  higher groupings or organisms originate, change,
  and go extinct

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How does heritable change come about?
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Darwinian Evolution

• the mechanism- natural selection
• the rate of evolution-gradual and steady

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What is the debate about?

• In sharp contrast, modern biologists consider
  evolution- the principle that the heritable
  traits of organisms change over time-itself an
  incontestable fact
• Can the small, random genetic changes observed
  today explain all of the various life-forms alive
  on the planet today?

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Brief History of Western Ideas on Origins
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Carolus Linnaeus (1707-1778)

• The father of modern taxonomy
• Kingdom, Phylum, Class, Order, Family, Genus,
  Species
• God creates, Linnaeus arranges
• Relatedness does not imply evolution in his mind
• Why do organisms fall so naturally into families?

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The Age of the Earth and Catastrophism

• James Hutton (1788)-Through geological studies
  suggested that the earth was far older than 6,000
  years
• Georges Cuvier (1812)- father of paleontology,
  suggested that God had created multiple times
  throughout the history of the earth
• Charles Lyell (1830) published Principles of
  Geology- Uniformitarianism

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Jean Baptiste Lamarck (1809)

• Proposed Evolution
• Mechanism was an inherent drive toward
  perfection and increased complexity, and from the
  felt needs of the organism

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Charles Darwin

• Studied for the Ministry at Cambridge in 1828 at
  age 19
• Ship naturalist on board the H.M.S. Beagle for 5
  years
• Published On the Origin of Species by Means of
  Natural Selection in 1859

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Various Evidences for Evolution?

• The Fossil Record
• Biogeography
• Comparative Anatomy
• Comparative Molecular Biology

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Interpreting Data as Evidence for Evolution

• Children look more like their parents than other
  people because they are descended from their
  parents and are genetically related. By analogy,
  organisms that look similar to one another are
  likely to be descended from a common ancestor

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Precambrian Era

• Origin of Earth until about 550 million years ago
• 3.5 billion years ago, prokaryotic-like fossils
• Multicellular organisms appear about 800 million
  years ago, including jellyfishes, corals, and
  worms, and unfamiliar organisms

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Paleozoic Era

• 550 million to 245 million years ago
• Organisms representing all 6 kingdoms present by
  the end of the era
• estimated 90 of species went extinct at end,
  perhaps due to the climate becoming much more dry

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Mesozoic Era

• 250-65 million years ago
• includes the age of reptiles land plants and
  animals diversify
• estimated 75 of species extinct

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Cenozoic Era

• 65 million years ago to present
• diversification of mammals, birds, insects, and
  flowering plants

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What does the fossil record mean?

• Organisms are distributed relatively consistently
  in rocks of the same age
• Some organisms that are intermediate forms
  between major classes are present
• Recent fossils generally look more like things we
  see today

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Biogeography

• Study of the past and present distributions of
  plant and animal species
• Reveals that endemic species are most closely
  related to nearby species, even if they live in a
  considerably different environment

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Comparative Anatomy

• homologous structures are ones that are
  physically similar
• they may have similar or very different functions

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• analogous structures- structures with similar
  functions that do not appear structurally related

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Vestigial Structures?
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Comparative Molecular Biology

• All cells use DNA as genetic information, RNA,
  ribosomes, and use approximately the same genetic
  code
• Comparisons of protein sequences used to
  establish relatedness
• Cytochrome C, 35 of 104 amino acids are the same
  in all organisms
• DNA/DNA hybridization

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The Mechanism of Evolution

• Why is mechanism important?
• Can random mutation and natural selection ,
  acting gradually over time, create new genera,
  families, and all the higher taxa?

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Darwins Natural Selection

• All species produce more offspring than will
  themselves survive to produce offspring (Struggle
  for Existence)
• Variation exists and much of the variation is
  heritable
• Adaptive traits are passed on differentially and
  may accumulate within a population

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Artificial Selection

• Can produce huge phenotypic variation
• Does not generate new species
• What is a species?

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Rate of Evolution

• Depends on selective pressure
• Depends on the extent of variation
• What if selection is strong but no individual in
  population has trait to give it an advantage
  under such conditions?