Evolution and Darwin

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Evolution and Darwin
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Theories

• A theory is
• a proposed explanation for a natural phenomenon.
• the body of interconnected concepts, supported by
  scientific reasoning and experimental evidence.
  (Lots and Lots of Evidence)
• solid ground of science
• A theory is a hypothesis that has not been
  rejected through experimentation and is a
  predictable phenomenon

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Charles Darwin

• Served as naturalist on mapping expedition around
  coastal South America and the world in 1831-1836.
• He traveled on the HMS Beagle
• Through observations and collected evidence
  during his voyage and 25 plus years of
  experimentation in England Darwin
• -Argued operation of natural laws
• produced change over time, evolution.
• -explained by natural selection

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Charles Darwin
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Darwins Evidence

• Fossils of extinct organisms were similar to
  modern species. Why had so many of these species
  disappeared?
• Characteristics of similar species varied from
  place to place. Why were there no rabbits in
  Australia? Why were there no kangaroos in
  England?
• Organisms on young volcanic islands (Galapagos)
  resembled those on mainland coast. Why?
• One could tell which island a tortoise came from
  by the shape of its shell. Why?

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Tortoises of the Galapagos
Pinta Island
Isabela Island
Hood Island
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Darwin

• Darwin suggested individuals with superior
  physical or behavioral traits are more likely to
  survive and reproduce, the struggle for
  existence, than those without such attributes.
• Selection
• artificial - domesticated breeds
• Corn
• Dogs
• natural - organisms in the wild
• Alfred Russel Wallace independently and almost
  simultaneously developed same idea 1858.

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Ideas that shaped Darwins Work

• James Hutton (1795) and Charles Lyell (1830)
• Geologists that described how the earth is very
  old can slowly change over long periods of time
• Jean-Baptiste Lamarck (1809)
• One of first to recognize living things have
  changed over time.
• Tendency towards perfection
• Use and Disuse
• Inheritance of Acquired Traits
• Thomas Malthus (1798)
• Observed human population growth and what
  controls it (war, famine, disease)
• Darwin applied his ideas to other species. Why do
  some individuals survive and reproduce and others
  do not?

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Darwin Finally Publishes His Work

• Published in 1859
• On the Origin of Species by Means of Natural
  Selection, or the Preservation of Favoured Races
  in the Struggle for Life

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Post-Darwin Evolution Evidence

• Fossil record
• Earth is older than previously believed
• Showed how species had changed and produced
  different species over time
• Geographic Distribution of Living Species
• Species on different continents with different
  ancestors, living in similar environments shared
  similar characteristics
• Mechanisms of Heredity
• modern genetics
• DNA

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Post-Darwin Evolution Evidence cont.

Molecular Evidence Molecular
Clocks Pylogenetic Trees
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Post-Darwin Evolution Evidence

• Comparative anatomy
• Homologous structures
• Have same evolutionary origin, but different
  structure and function.
• Analogous structures
• Have similar structure and function, but
  different evolutionary origin.

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Homology Among Vertebrate Limbs
Analogous structures
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Summary of Darwins Theory

• Individual organisms differ, and some of this
  variation is heritable.
• Organisms produce more offspring than can
  survive, and many that do survive do not
  reproduce
• Because more organisms are produced than can
  survive, they compete for limited resources.
• Each unique organism has different advantages and
  disadvantages in the struggle for existence
• Species alive today are descended with
  modification from ancestral species that lived in
  the distant past. All from a common ancestor. A
  single tree of life