Squirrels live in forests where foxes also live. Foxes hunt squirrels for food. Squirrels that have fur that is the same color as the trees are harder for the foxes to see and catch.
The diagram below shows a population of squirrels that live in a forest. At time 1, the population had the same number of black and gray squirrels. At time 2, after many generations, there were many more black squirrels and fewer gray squirrels in the population.
2 diagrams, each containing rows of squirrel icons. The first diagram is titled Population at Time 1 and contains 2 rows of 5 squirrel icons each, one labeled Black and one labeled Gray. The second diagram is titled Population at Time 2 and contains 2 rows of squirrel icons. The first row is labeled Black and contains 9 squirrel icons. The second row is labeled Gray and contains 2 squirrel icons. An arrow points from the first diagram to the second diagram and is labeled: After Many Generations.
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11. How did the environment change between time 1 and time 2? How did the population change?
Responses
a
You cannot tell how the environment changed. With each generation, more squirrels passed on the gene for black fur to their offspring.
You cannot tell how the environment changed. With each generation, more squirrels passed on the gene for black fur to their offspring.
b
There were more black trees. Squirrels with black fur are more likely to survive, so the squirrels with gray fur changed to have black fur.
There were more black trees. Squirrels with black fur are more likely to survive, so the squirrels with gray fur changed to have black fur.
c
There were more black trees. Squirrels with black fur are more likely to survive, so both types of squirrels passed on the gene for black fur to their offspring.
There were more black trees. Squirrels with black fur are more likely to survive, so both types of squirrels passed on the gene for black fur to their offspring.
d
There were more black trees. With each generation, more squirrels with black fur survived long enough to pass on the gene for black fur to their offspring.
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The best response is:
d There were more black trees. With each generation, more squirrels with black fur survived long enough to pass on the gene for black fur to their offspring.
This response accurately attributes the change in the population to the advantages provided by the environment, where the black fur aligns with the color of the trees, allowing black squirrels to be less visible to foxes and increasing their survival and reproductive success.
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