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.
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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.
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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.
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

Prediction 1 is best. This is because, with the introduction of a green environment, snakes with green skin would be better camouflaged and therefore more likely to survive and reproduce. This scenario illustrates natural selection: as snakes with the green skin trait survive and pass that trait onto their offspring, the frequency of green snakes in the population would increase over generations.

Here is a brief explanation of why the other options don't hold up:

• Prediction 2 (options c and d) suggests that green-skinned snakes would not survive and therefore would not reproduce. However, considering the new environment with green plants, it is more likely that green snakes would indeed have an advantage.

• Option b also mentions the possibility of yellow and red snakes having offspring with mutations, but this scenario assumes that mutations would come about in response to the environment, which is not how evolution typically works. Instead, individuals with beneficial mutations (like green skin) would naturally emerge and thrive.

So, the most accurate response is that Prediction 1 best represents the expected outcome after many generations due to natural selection favoring green snakes in a green environment.