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EVOLUTION
UNIT 7A
Part 1 of 2
DARWIN, NATURAL SELECTION,
HARDY-WEINBERG
Ch. 1 (p. 8-13) and Ch. 13 (all)
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All life is connected.
The basis for this kinship is
evolution
Evolution has transformed life
on Earth from its earliest
beginnings to its extensive
diversity today
Evolutionary view came into
focus in 1859 with Darwin’s
book
Photo on left is Charles
Darwin (1809-1882)(British
biologist) with son William in
1842.
One of Britain’s most
renowned biologists
Published The Origin of
Species 17 years later.
Was the the most influential
scientist in the development of
modern biology.
Buried next to Isaac Newton
in London’s Westminster
Abbey.
• 2 main points in book:
• 1) species living today
descended from ancestral
species = “descent with
modification” = evolution
• Ex: the diversity of bears is
based on different
modifications of a common
ancestor from which all bears
descended.
• 2) the mechanism for
evolution is “natural
selection” (see next slides)
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Darwin loved nature. Disliked medical school. Became a minister. Became a
naturalist for a voyage around the world when he was 22 years old.
Darwin’s “Voyage of the HMS Beagle” is shown above.
Observed and collected thousands of specimens. Observed adaptations of organisms.
Most of animals of Galapagos Islands live nowhere else in world, but they resemble
species living on the South American mainland. It was as though the animals strayed
from mainland, then diversified as they adapted to environments on the different
islands.
• Darwin saw large diversity of animals on
Galapagos Islands, off coast of South America
• If an ocean separated islands, it isolated 2
populations of a single species. The populations
could diverge more and more in appearance as
each adapted to local environmental conditions.
• After many generations, 2 populations could
become dissimilar enough to be separate species
- 14 species in the case of the birds called
Galapagos finches. (This is now called
divergent evolution)
• They have beak shapes and colorations that are
adapted to their environments
• The beaks are adapted to certain food sources
on the different islands; the colors protect them
from predators
• See next page for the finches!