Evidence of Evolution

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Evidence of Evolution
From, Darwins , 1839, Birds Part 3 No. 3 of The
zoology of the voyage of H.M.S. Beagle.
illustration by John Gould
From Darwins Transmutations of Species, 1837.
The first family tree
Charles Darwin
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The Fossil Record
1) Shows which organisms once existed

• 99.9 of all species that ever existed are now
  extinct

Trilobytes 405 million years ago
The oldest fossil record of multicellular life,
filaments of Bangiomorpha, a red algae, are 1.6
billion years old
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2) Indicates when the organisms existed

• radiometric dating is used to determine age of
  fossils

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• 3) Shows a logical sequence of forms
• invertebrates
• fish
• amphibians
• reptiles
• mammals and birds

Pterodactyl then Bird
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4) Shows transitional forms between species
Transitional Forms fossils or organisms that
show intermediate states between an ancestral
form and that of its descendants There are
numerous examples of transitional forms in the
fossil record
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Pakicetus was a land mammal, Aetiocetus a
transitional species, and the gray whale a modern
species
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Transitional stages occur between modern horses
(Equus) and the four-toed Hyracotherium
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There are 3 elephant species living today. The
fossil record shows that 350 species used to exist
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Eupodophis lived 92 million years ago and had
legs its a transitional form between lizards
and limbless snakes
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Comparative Anatomy
Shows evolutionary relationships between groups

• homologous structures similar structures
  because of
• common descent

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Whales and hummingbirds have tetrapod skeletons
inherited from a common ancestor. Their bodies
have been modified and parts have been lost
through natural selection. On the surface, these
animals look very different, but the relationship
between them is easy to see
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Frogs, birds, rabbits and lizards all have
different forelimbs, reflecting their different
lifestyles. But those different forelimbs all
share the same set of bones - the humerus, the
radius, and the ulna. These are the same bones
seen in fossils of the extinct transitional
animal, Eusthenopteron, which demonstrates their
common ancestry
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Comparative Embryology

• closely related organisms go through
• similar stages in their embryonic
• development

Embryology the study of embryo
development Ontogeny the development of an
organism from egg to adult form
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• Similarities/differences in ontogeny
• help establish evolutionary
• relationships (phylogeny)
• Phylogeny the evolutionary history of a group
• of organisms

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• Early embryos of many different vertebrate
• species look remarkably similar

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• note that human embryos have similar blood
• vessel structure as a shark

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Molecular Biology

• evolutionary relationships are reflected in the
• DNA and proteins of organisms closely
• related organisms have similar DNA
• sequences

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• Comparison of mammalian genomes, using either
  whole genomes or just
• introns, Sung-Hou Kim lab/UC Berkeley

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• Mutations occur at a fairly predictable rate.
• Therefore, the similarity/differences in base
  
• sequences of DNA reveal the evolutionary
• history of species

nucleotide substitutions among 17 mammal species
from seven gene products versus time of
divergence according to fossil records
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• Mutation rates
• bacteria 10-8 /bp/generation
• DNA Viruses 10-6 to 10-8/bp/generation
• eukaryotes 10-4 to 10-6/bp/generation
• humans 4.8 x 10-9 /bp/generation

bp base pairs
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• changes in the base sequences of SARS virus
• show relationships between various strains of
  the
• virus, and shows that the virus jumped from
  bats
• to civets (a cat) and humans

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Evolutionary tree of HIV-1 shows how the virus
hopped from chimpanzee hosts to humans. HIV-1 is
most closely related to the SIV virus that
infect chimps
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There are about 100 breeds of domestic cats. All
originated from the African Wildcat, Felis
sylvestris. Modern cats appear to have
originated in Asia 10 million years ago.
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Biogeography

• the geographic distribution of species
• suggests evolutionary relationships

Biogeography the study of the geographic
distribution of species
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The marsupials of Australia are thought to have
migrated from South America and across Antarctica
to Australia (arrow) by way of land bridges, some
70 million years ago