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DARWIN’S VOYAGE:
Notes from the reading, pp. 140-150
DO NOW: Give one example of how sunflower seed variation can lead to natural selection
---------------------------------------------------------------------------------------------------------------------------------------Guide for Reading Questions:
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How did Darwin explain the differences between species on the Galapagos Islands?
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How does natural selection lead to evolution?
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How do new species form?
Stop here!
Introduction: p 140
 December 1831, British ship: HMS Beagle- sailing around the world
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Darwin: 22 year old companion turned naturalist
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Observed plants and animals- lead to theory of natural selection
Darwin’s Observations: p 141
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Observed A LOT of diversity
He saw bones of animals that had died long ago and inferred that they looked like other animals that he
studied
What happened to these creatures of the past?
Arrived at the Galapagos Islands
Similarities and Differences: p 142
 G Islands had many similar plants and animals to the mainland
There were also many differences:
 Cormorants—on the mainland, they flew, on G. Islands, they could not
 Iguanas—on G. Islands has large claws, on mainland, they were smaller
Inference: Somehow the organisms from the mainland moved to the G. Islands and eventually their offspring
became different from the mainlanders
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Tortoises—dome-shaped and saddle-shaped shells on different G Islands
Adaptations: p 143
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Finches: Darwin observed that the birds beaks were best suited to what it ate
Evolution: p 143-144
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Darwin thought that species gradually changed over many generations and became better adapted to the
new conditions
Evolution = gradual change over time
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Darwin knew that people used selective breeding to make organisms with desired traits (like dogs or
sheep)
Natural Selection: p 144-145
Natural Selection= process by which individuals that are better adapted to their environment are more likely to
survive and reproduce
Factors that affect natural selection:
1. Overproduction: having more offspring than can survive
2. Competition: competing for limited resources
3. Variations: differences among species
The Role of Genes in Evolution: p 148
Variations can result from:
 Passing on of dominant or recessive traits
 Mutations
*** only traits that are inherited can be acted upon by natural selection (not acquired!)
Evolution in Action: p 148
Real time examples:
(1) Finches beaks; population changed when the rain levels changed
Less rain  plants died  finches that ate smaller seeds had little food  finches with stronger beaks could eat
large-thorny seed pods
(2) Peppered Moths Example
How Do New Species Form: p 149
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Isolating a species by landform or man-made structures  can no longer mate
These groups may evolve with different traits and have variation
Continental Drift: p 150
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Animals were able to migrate around Pangaea  continents separated  species isolation
Marsupials: many found in Australia and not found anywhere else
Madagascar: Dr. Pearlman discussed how many organisms could be found there but no where else