Chapter 21
Self-Quiz
Unit 4: Evolution
Adaptation and Speciation
Review
result from the process of natural
in which organisms with favorable
traits have better able to survive and reproduce.
Examples of adaptations include the complex nest
behavior of
Weaver Ants,
the spring and summer
of the
Nemoria arizonaria
caterpillar, and insect
of many
orchids.
Evolution allows organisms to adapt quickly to changing
. Examples include the
Soapberry Bug
developing shorter
to access
smaller
food sources, and
ground finches
in the
Galapagos
developing
bigger
when small seeds are
scarce.
Sexual selection of male traits are often balanced by exposure to predators in an ecological
: the conflicting demands of individual survival and reproduction result in complex selection pressures. Examples include the brightly colored
Trinidad
Guppy
and the
singing
of birds.
A species can be biologically defined as a group of
natural populations that are
isolated from other such groups.
Reproductive
isolation can arise from two types of barriers.
barriers prevent zygotes from forming, and include
isolation,
isolation,
and
isolation.
barriers prevent fertilzed zygotes from developing into viable reproductive adults, and include zygote
and
infertility.
Accumulated genetic differences between separate populations of a species can lead to reproductive
isolation
and to the appearance of new species, or
.
Geographic
isolation that reduces gene flow between populations can lead to
speciation. An example is
Snapping Shrimp
of
Panama.
In the absence of geographic isolation,
speciation can occur due to other isolation factors such as
plant preference in
Apple Maggot Flies
and mating
difference in
Field Crickets.
Adaptation and speciation form the basis for the
diversity
of life.
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Feb 21, 2006
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