There is a kind of snake that can be born with red, yellow, or green skin. Eagles hunt these snakes, but snakes that are the same color as their environment are harder for the eagles to see and catch.

Question

Diagram titled Population Before containing 2 rows of snake icons. The first row is labeled Yellow and contains 3 snake icons. The second row is labeled Red and contains 8 snake icons.
A population of snakes once lived in an environment where there was sand and dirt, but no grass. The image above shows what the population looked like then. The environment changed so that green grasses and plants now grow there.

The diagrams below show two predictions for what the population could look like after many generations.

Diagram titled Prediction 1 (Many Generations Later) containing 3 rows of snake icons. The first row is labeled Yellow and contains 2 snake icons. The second row is labeled Green and contains 8 snake icons. The third row is labeled Red and contains 2 snake icons.
Diagram titled Prediction 2 (Many Generations Later) containing 2 rows of snake icons. The first row is labeled Yellow and contains 2 snake icons. The second row is labeled Red and contains 11 snake icons.
4. Which prediction best shows what the population could look like after many generations? What caused it to change?
Responses

a
Prediction 1 is best. Two yellow or red snakes had a baby with a mutation in its genes for the green-skin trait. Because green snakes are more likely to survive, that baby survived long enough to pass on its mutation, so the green trait became more common over generations.
Prediction 1 is best. Two yellow or red snakes had a baby with a mutation in its genes for the green-skin trait. Because green snakes are more likely to survive, that baby survived long enough to pass on its mutation, so the green trait became more common over generations.

b
Prediction 1 is best. Green snakes are more likely to survive, so yellow and red snakes began to have offspring with mutations in their genes for the green-skin trait so that their offspring would have a better chance of surviving.
Prediction 1 is best. Green snakes are more likely to survive, so yellow and red snakes began to have offspring with mutations in their genes for the green-skin trait so that their offspring would have a better chance of surviving.

c
Prediction 2 is best. A snake could have been born with a mutation in its genes for the green-skin trait and lived for a little while. Because green snakes are more likely to die, it would have been more likely to die before it had offspring, so the final population will only have yellow and red snakes.
Prediction 2 is best. A snake could have been born with a mutation in its genes for the green-skin trait and lived for a little while. Because green snakes are more likely to die, it would have been more likely to die before it had offspring, so the final population will only have yellow and red snakes.

d
Prediction 2 is best. A snake could have been born with a mutation in its genes for the green-skin trait, but having a mutation in its genes would have caused it to die when it was born, so the final population will only have yellow and red snakes.

Answer 1

The best response is:

a
Prediction 1 is best. Two yellow or red snakes had a baby with a mutation in its genes for the green-skin trait. Because green snakes are more likely to survive, that baby survived long enough to pass on its mutation, so the green trait became more common over generations.

This response accurately explains the process of natural selection. Given the new green environment, snakes that blended in with their surroundings were less likely to be seen and hunted by eagles, thus increasing their chances of survival and reproduction. The prediction reflects the increased frequency of the green trait in the population over many generations due to this selective pressure.