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AP Bio
AP Bio Unit 7
Ch. 17
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Microevolution is a change in
allele frequencies
within a
population
Microevolution does not lead to the
formation
of
new species
Macroevolution, or the origin of a
new species
, results from the
accumulation
of
microevolutionary changes
over time
Darwin
dedicated his life to understanding how new species
originate
Speciation
is a form of macroevolution
Taxonomists
are scientists who classify organisms into groups
Species can be defined in various ways, including:
Morphological Species
Concept
Evolutionary Species
Concept
Phylogenetic Species
Concept
Biological Species
Concept
Morphological Species Concept:
Species are distinguished by distinct
physical characteristics
Helpful for
paleontologists
Challenging for
microorganisms
and
cryptic species
Evolutionary Species Concept:
Members share a distinct
evolution
in addition to
morphological traits
Used
to
indicate speciation
in the
fossil record
Phylogenetic Species Concept:
Smallest set of
interbreeding
organisms that share a
common ancestor
Monophyletic
branch in the phylogenetic tree
Considers
DNA
and other factors
Biological Species Concept:
Relies on
reproductive isolation
to identify different
species
Reproductive isolation
defined by
physiological
,
behavioral
, and
genetic
processes
Reproductive Isolating Mechanisms:
Prezygotic
Isolating Mechanisms:
Geographic
Isolation
Habitat
/
Ecological
Isolation
Temporal
Isolation
Behavioral
Isolation
Mechanical
Isolation
Gamete
Isolation
Postzygotic
Isolating Mechanisms:
Hybrid Inviability
Hybrid Sterility
Allopatric Speciation
is the most common form of speciation:
Species separated by a
geographical
barrier
Undergo different
selection pressures
Competition leads to
resource partitioning
Sympatric
Speciation
:
Speciation without a
geographic barrier
Involves divergence in
diet
or
microhabitats
Polyploidy is more likely in
plants
Adaptive Radiation:
A single
ancestral species
gives rise to a variety of
new species
Often involves
sympatric species
and
ecological release
Convergent Evolution:
Occurs when
biological traits evolve
in two
unrelated species
due to exposure to
similar environments
Examples include African lake fish with similar coloring/body
Principles of Macroevolution:
Gradualistic
model
Punctuated equilibrium
model
Developmental Genes
and
Macroevolution
Developmental Genes and Macroevolution:
Control switches for
development
are shared among
all organisms
Examples include the
Pax6
gene for the eye and
Tbx5
gene for limbs
Human Evolution:
Humans have approximately
23,000
genes
Natural selection acts on
variations
that are already
present
Macroevolution is not goal-oriented but
opportunistic