Transcript Natural Selection

Natural Selection
Life’s diversity and connections
Evolution
• A change over a period of time
• A collection of facts, observations and
hypotheses about the history of life
Diversity
• What scientific process accounts for:
– The millions of species alive on earth now
– The hundreds of millions of species that are
extinct
– No two individuals are exactly alike (with few
exceptions)
– The molecular instructions for life are the same
Answer started in December
1831
• The voyage of the Beagle its five year
mission to boldly go where no man has
gone (sorry). It was a surveying trip
• Naturalist on board: Charles Darwin
Evidence of diversity
• Darwin made collections everywhere they
stopped
• Identified a few specimens on board, but
sent most back to England for experts to
identify
• Collected many fossils everywhere they
stopped if possible
Evidence of diversity
• Noticed that traits and behavior together
help organisms adapt to where they live
• Individuals must be able to survive and
reproduce to be successful
Evidence of diversity
• Technical terms for all this: living diversity
(the variety of living things), fossil diversity
(the variety of fossilized creatures),
ADAPTATION (the physical and behavioral
traits that enable organisms to survive),
FITNESS ( the ability of an individual to
survive and pass on genes to its offspring)
The Galapagos Islands
• Last stop before the long trip across the Pacific
(see map page 451)
• Darwin attempts to reconcile:
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Believe vs. observation
Evidence of diversity vs. genesis
Evidence of fossils and geology vs. constant earth
Malthus’s evidence of reproductive success
Anatomy evidence of homologous structures and
vestigial structures
Others thinking about change
• Hutton and Lyell
– Geology
• Lamarck
– Biology
• Malthus
– Biology