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I. Early Models of Evolution
A. evolution - changes in inherited
characteristics over time
B. scientists use the fossil record to trace the
evolution
of some organisms
C. Theory
of Acquired Characteristics
1.
proposed by Jean Baptiste de Lamarck in 1809
2.
belief that traits developed during the parent's lifetime
were passed to the offspring
3.
scientific data did NOT support this theory and it was rejected
II. Darwin's Model of Evolution
A. 1831- Charles Darwin sailed from
England to the
South
American coast and the Galapagos Islands
B. Darwin's Observations
1. he
observed 13 species of finches on the Galapagos Islands
2.
the finches were similar but differed in beak type
and eating habits
3. Darwin reasoned that...
a. the finches compete for food, space and other resources
b. those best suited for survival are most likely to reproduce
and pass on their traits (survival of the fittest)
c. finches with beak shapes that allow them to eat the
available food will survive better and pass on their traits
d. different islands have different food sources, therefore
different beak shapes survived on different islands
e. eventually different islands formed different species
C. Natural Selection
1. the
theory that states that organisms with traits best suited
for their environment are more likely to survive
and reproduce to pass on their traits
2. The
Principals of Natural Selection
a. more offspring are produced than can survive
b. differences or variations occur among individuals of a species
c. variations are passed on to offspring
d. helpful variations help in survival and increase the
chances of reproducing
e. over time, individuals with variations
become a separate species
D. The Speed of Evolution
1. Gradualism
- a model of evolution in which one species
slowly and steadily evolves into another
2. Punctuated
Equilibrium - a model of evolution in
which one species suddenly changes into another
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