Natural
Selection
Summarize the observations and deductions that
make up the theory of natural selection.
Pattern:
organisms fit their environment
Process:
More born than survive, individuals vary, variation is heritable, survival is
non-random – population changes: ie, success of “favored forms” in the struggle
for existence and transmission of those variations to the next generation
Ability of an
individual to survive and reproduce in its environment – compared to other
individuals of the same species in that environment.
a
trait that increases fitness relative to other individuals in the same
population (who lack the trait). Often
these traits are ones that increase access to a limiting resource.
Know that natural selection “works” on
individuals, but results in changes in populations.
The population becomes adapted to the
environmental conditions.
Example: Rosemary and Peter Grant’s work
on Galapagos finches.
Distinguish “inheritance of acquired
characteristics” from natural selection and be able to correct misstatements
about natural selection.
Explain that “selection” does not imply a
conscious act, choice or goal seeking.
Natural selection is
not purposeful, nor does it drive toward a particular “goal” – it only makes
organisms better adapted to their current environment.
Natural selection
produces “better” organisms only in the sense of better fit for environment of
selection.
Acts
are not “for the good of the species” and should not be interpreted that
way. Purely altruistic acts are “dead
ends” in most species.
Connect
your understanding of the process of natural selection to your understanding of
genes, alleles, mutations, and inheritance.
Evolution results from
genetic changes that are acted on by natural selection
The origin of species
and higher taxa can be explained in terms of natural selection acting on
individuals
The postulates of
natural selection can be reformulated into the language of genes (Evolution –
change in the frequency of alleles in a population over generations)
Natural selection is
not the only process that can cause changes in gene frequency.