Natural Selection and Adaptation

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Natural Selection and Adaptation
Natural selection can be defined as the sum
total of environmental forces or pressures
that determine fitness. Malthus perils of
overpopulation geometric increase Darwin
elephants - Individuals best suited to the
environment will be the ones that manage
to survive and reproduce - Variation under
domestication artificial selection Natural
selection the analogue to artificial
selection. 1. Competition for finite
resources and harsh physical realities
2. Limitations on those who reproduce 3.
Result preferential survival and reproduction

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Adaptation
Adaptation is a noncreationist explanation of the
apparent design in nature. Adaptation
results from a change in form through time which
reflects changing adaptations resulting from
natural selection. With natural selection,
not all individuals contribute equal numbers
of offspring to the next generation.
Traits that enhance survival and reproduction
will tend to increase in frequency from
generation to generation. Such traits are
adaptive which makes those who carry them more
fit.
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Genetics and evolution
Darwin Natural selection operated on
individuals and fitness also applied to
individuals. However, genetics was not part of
Darwins thinking. Modern evolutionary biologists
think of natural selection as favoring or
discouraging particular traits. Mendel
demonstrated that inheritance was not a blending
process, as Darwin believed. Mendel
demonstrated that inheritance involved discrete
units or particles (which we now call genes)
which retain their integrity from generation to
generation. genotype the complete set of
genes an individual possesses phenotype all
observable traits of an individuals appearance
and behavior
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Genetics an evolution
Gene pool the complete set of genes that
characterizes a species or breeding
population. Evolution Darwin - descent
with modification today - change through
time in allele frequencies in a
population. Population a group of organisms in
the same species that regularly breed
together
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Evolutionary forces

• How does the gene pool change?
• 1. The simplest change the adding of new
  genetic material or gene.
• 2. The majority of gene pool changes are not the
  result of adding new genes but are instead the
  result of
• changing frequencies of genes already
  present.
• The actual course that evolutionary changes takes
  depends on 2 things
• Partly on the genes already present in the gene
  pool I.e., evolution is opportunistic
• Partly on the cause of the gene pool change.
• Forces that cause change in the gene pool
  mutation, natural selection, migration, and
  accidents of sampling (random genetic drift,
  the Founder effect, the bottleneck effect).