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EVOLUTION
Some history on the
theory of evolution
Early theories (pre-1700’s and 1700’s)

nature is seen as not changing and having originated
through spontaneous generation (pre-1700’s)

Comte de Buffon (1707-1788) talked about possible
common ancestry of humans and apes

Linnaeus was the first one to
try to classify life (1735,
placed us with primates)

Erasmus Darwin discussed competition
and sexual selection
More developments in the 1700’s

an understanding of the age of the Earth
develops through geology

inheritance of acquired traits (use and disuse)
ex. Baby giraffes are born with long necks
because their parents stretched their necks to
reach leaves (Jean-Baptiste Lamarck, 1801)
Other contributions

Thomas Malthus – plants and animals produce more
offspring than can survive (led to Darwin’s formulation
his theory of natural selection)

Georges Cuvier – studied fossils/established that
extinctions occur

Charles Lyell – geologist who rejected catastrophism;
suggested gradual geologic changes (uniformitarianism)
– similar to evolution
Thomas Huxley – supported natural selection; applied
evolution to humans

Darwin and the Voyage of the
Beagle
 in
December, 1831’ Charles Darwin, a
naturalist in his 20’s began a 5-year
journey around the world on a ship called
HMS Beagle
 Darwin’s
role was to
observe, record, and
collect specimens of
rocks, minerals, plants, and animals
Darwin: PBS

Darwin collected 1000’s of specimens and
shipped them to England, mainly from South
America and a chain of volcanic islands called
Galapagos

he collected them but did not realize what he
was seeing until years later (ex. didn’t catalogue
the finches very well, ate turtles that would later
support his theories, etc.)

Darwin spent the next 20 yrs analyzing his
findings in light of artificial selection (ex.
breeding of pigeons, breeding of dogs, etc.)
Darwin’s Finches
 Arrival
 Success
 Competition
 Diversity
&
Opportunity
 Radiation
How does evolution really work?
http://www.pbs.org/wgbh/evolution/educators/teachstuds/svideos.html
 Hawaiian
honeycreeper
Natural Selection defined:
 The
process in nature by which, according
to Darwin's theory of evolution, only the
organisms best adapted to their
environment tend to survive and transmit
their genetic characteristics in increasing
numbers to succeeding generations while
those less adapted tend to be eliminated.
Darwin’s theory of evolution
A
theory that explains the origin of species
(not life)
 At
the genetic level, it is the theory of
change in the inherited traits of a
population of organisms through
successive generations
 Or
as Darwin would have put it: descent
with modification from a common ancestor
 This
modification or change through
successive generations come from
variation in a population
 Variation
comes from mutations and
genetic recombination (e.g. crossing
over).; both can be passed on to the next
generation (more on this later)
Misconception: “Evolution is a
theory about the origin of life.”
 Evolution
its origin.
deals with how life changed after
Misconception: “Evolution is like
a climb up a ladder of progress;
organisms are always getting
better.”
 “good
enough” is just that – there is no
“perfect” organism, your ability to survive
will vary with environment
Misconception: “Evolution
means that life changed ‘by
chance.’ ”
 Mutations
not.
are random, natural selection is
Misconception: “Natural
selection involves organisms
‘trying’ to adapt.”
 Natural
selection is based on variation
within a population and selection, not
trying.
Misconception: “Natural
selection gives organisms what
they ‘need.’ ”
 Natural
selection has no intent.