Problem :
What is the difference between geographical isolation by vicariance and by
dispersal?
The difference between isolation by vicariance and dispersal is when the
geographical barrier appeared relative to the distribution of the populations.
Isolation by vicariance occurs when a population that is already widely
distributed is divided by the appearance of a barrier. Dispersal occurs when
part of a population crosses a barrier that already exists.
Problem :
A farmer plants two crops of the same plant three weeks apart. The first crop
each crop flowers for about a week, approximately four weeks after planting.
What type of reproductive isolation would you expect to find between these two
populations?
These two populations will be temporally isolated. If each crop flowers for only
a week and they were planted three weeks apart, the first crop will stop
flowering a full week before the second crop starts to flower.
Problem :
The male of a given species of frog uses distinctive calls to attract mates. Two
populations of these frogs coexist in a single pond but never interbreed because
their mating calls are different. Females of one population will not respond to
the calls of a male of the other populations. What type of reproductive
isolation is this?
This is an example of behavioral isolation. The two species cannot interbreed
because their calls, a type of courtship behavior, are different.
Problem :
Describe gametic isolation.
In gametic isolation, no physical or behavioral barriers to mating exist.
Members of two different species mate, but do not produce offspring because
their gametes are unable to fuse to form a zygote.
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