Darwin and Lamarck

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Lamarck and Darwin

Varying Views of Evolution

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French naturalist Jean-Baptiste de Lamarck (1744-1829)

“The theory of

Acquired Traits”

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Lamarckism #1

Giraffe seeks food, and stretches its neck to acquire the leaves

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Lamarckism #2

Continual stretching results in longer neck. Longer neck is passed on to offspring.

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British naturalist Charles Darwin (1809 –1882)

“The theory of

Natural Selection”

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Influences on Darwin

1. British tradition of selective breeding of livestock and domestic pets

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Influences on Darwin

2. Observations made while serving on HMS Beagle during a journey to the Galapagos Islands (1831 – 1836).

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Galapagos Islands

900 km to Ecuador

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Darwin’s Finches

Darwin observed differences in the beaks of finches on the islands. He assumed the finches all descended from common ancestors that migrated from the mainland.

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Slide 11

Natural Selection: Variation within Offspring

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Natural Selection

Selective Advantage:

The variation provides an advantage to one of the offspring. The others will not pass on their genes.

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Questions that Darwin Couldn’t Answer

What was the source of variation within a species? (genes, alleles)

How did new traits arise? (mutations)