Background: Two related species of plants live on a mountainside. The San Gabriel High Rose lives from the middle of the
Posted: Wed May 18, 2022 1:46 pm
Background: Two related species of
plants live on a mountainside. The San Gabriel High Rose lives from
the middle of the mountain to the very top; opens its flowers from
the afternoon until the evening; has yellow and red flowers; and is
pollinated by both birds and butterflies. The San Gabriel Low Rose
lives from the middle to the bottom of the mountain; opens its
flowers from morning to afternoon; has yellow and red flowers; and
is pollinated by both birds and butterflies. You study a population
in the middle of the mountain where both species overlap, and find
that here, the High Rose has only yellow flowers, opens its flowers
in the late afternoon, and is butterfly-pollinated. In contrast, in
this population, the Low Rose has only red flowers, opens its
flowers in the morning, and is bird-pollinated. You experimentally
hand-cross the two species and plant seeds in the middle of the
mountain; compared to the pure parent species, hybrid plants grow
poorly and have low fitness.
Question: Explain why the two plants
evolved differences in the middle of the mountain that are not seen
at the top or bottom of the
mountain, Describe the variability that was
initially present in your starting
population. [Hint: this is asking what it was
like when the species initially began to overlap with each
other.] State which individuals had the highest fitness, and
why. Explain what evolutionary force(s) acted on the
population, and why and how it acted. [Hint:
there may be several forces acting at the same
time; name whatever forces seem reasonable to explain the change
you describe in the following sentence.] Describe how the
population evolved. Be as specific as you can (e.g., say
“increased” or “decreased”, rather than just “changed”.)
plants live on a mountainside. The San Gabriel High Rose lives from
the middle of the mountain to the very top; opens its flowers from
the afternoon until the evening; has yellow and red flowers; and is
pollinated by both birds and butterflies. The San Gabriel Low Rose
lives from the middle to the bottom of the mountain; opens its
flowers from morning to afternoon; has yellow and red flowers; and
is pollinated by both birds and butterflies. You study a population
in the middle of the mountain where both species overlap, and find
that here, the High Rose has only yellow flowers, opens its flowers
in the late afternoon, and is butterfly-pollinated. In contrast, in
this population, the Low Rose has only red flowers, opens its
flowers in the morning, and is bird-pollinated. You experimentally
hand-cross the two species and plant seeds in the middle of the
mountain; compared to the pure parent species, hybrid plants grow
poorly and have low fitness.
Question: Explain why the two plants
evolved differences in the middle of the mountain that are not seen
at the top or bottom of the
mountain, Describe the variability that was
initially present in your starting
population. [Hint: this is asking what it was
like when the species initially began to overlap with each
other.] State which individuals had the highest fitness, and
why. Explain what evolutionary force(s) acted on the
population, and why and how it acted. [Hint:
there may be several forces acting at the same
time; name whatever forces seem reasonable to explain the change
you describe in the following sentence.] Describe how the
population evolved. Be as specific as you can (e.g., say
“increased” or “decreased”, rather than just “changed”.)