I. Naturalism
...
Natural selection states
that chance variations exist between individuals, and that advantageous variations�those that increase an individual's fitness for the environment�afford the most opportunity for reproductive success.
The modern synthesis model (neo-Darwinism) accounts
for mutation and recombination as mechanisms of variation and considers differential reproduction
to be the mechanism of reproductive success.
Inclusive fitness considers
an organism's success to be based on the number
of offspring, success in supporting offspring, and the ability of the offspring to then support others;
survival of offspring or relatives ensures continuation of genes in subsequent generations.
Punctuated equilibrium considers
evolution to be a very slow process with intermittent rapid bursts of evolutionary activity.
II. Different types of selection
lead to changes in phenoty pes.
Stabilizing
selection keeps phenotypes in a narrow range, excluding extremes.
Directional selection
moves the average phenotype toward one extreme.
Disruptive selection
moves toward two different phenotypes at the
extremes and can lead to speciation.
Adaptive radiation
is the rapid emergence of multiple species from a
common ancestor, each of which occupies its own ecological niche.
III. Species
...
A species
is the largest group of organisms capable of breeding to form fertile
offspring.
Species are reproductively isolated from each other by pre- or postzygotic mechanisms.
IV. Two species can evolve with
different relationship patterns.
a. Divergent evolution
occurs when two species sharing a common ancestor become more different
b. Parallel evolution
occurs when two species sharing a common ancestor evolve in similar ways due to analogous selection pressures.
c. Convergent evolution
occurs when two species not sharing a recent ancestor evolve to become more similar due to analogous selection pressures.
d. According to the molecular clock model, the degree of difference in the genome between two species is related to
the amount of time since the two species broke off from a common ancestor.