Natural Selection - Critical Juncture Assessment

Blue jays are birds that live in the forest. They can have beaks of different thicknesses. Blue jays use their beaks to get to the seeds they eat. Blue jays with thinner beaks can easily reach and eat the seeds inside pinecones. Blue jays with thicker beaks can easily open and eat seeds with hard shells.

The diagrams show three possible blue jay populations whose environment changes to have only seeds in pinecones, which of the following blue jay populations will most likely survive?

• Populations 1 and 2 will most likely survive.

• Populations 2 and 3 will most likely survive.

• Only Population 2 will survive because it is the only population with variation.

• All the populations will survive because the blue jays will change the thickness of their beaks if they need to.

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3. Hummingbirds can have beaks of different lengths. They use their beaks to reach to the nectar (their food) at the bottom of flowers. Hummingbirds with longer beaks can get food from long flowers. Hummingbirds with shorter beaks cannot reach the nectar in long flowers. If a hummingbird can’t easily reach its food, it will die. The population of hummingbirds once lived in an environment where there were very few long or medium flowers. The top image shows what the population looked like then. The environment changed so that mostly long and medium flowers now grow there. The diagrams below show two predictions for what the population could be like after many generations.

Which prediction best shows what the population could look like after many generations? What caused it to change?

• Prediction 1 is best. Two hummingbirds with short or medium beaks had a baby with a mutation in its genes for the long-beak trait. Because long-beak hummingbirds are more likely to survive, that baby survived long enough to pass on its mutation, so the long-beak trait became more common over generations.

• Prediction 1 is best. Hummingbirds with long beaks are more likely to survive, so hummingbirds with short and medium beaks began to have offspring with a mutation in its genes for the long-beak trait so that their offspring would have a better chance to survive.

• Prediction 2 is best. A hummingbird could have been born with a mutation in its genes for the long-beak trait and lived for a little while. Because long-break hummingbirds are more likely to die, it would have been more likely to die before it had any offspring, so the final population will only have medium or short beak hummingbirds.

• Prediction 2 is best. A hummingbird could have been born with a mutation in its genes for the long-beak 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 medium or short beak hummingbirds.

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Guppies are small fish that live in South American rivers. They can have differentsized spots on their bodies. The river bottoms are covered in rocks. Guppies with spots that are the same size as the rocks on the bottom are harder for bigger fish to see and catch. The diagrams below show three possible guppy populations. Which population has more variation?

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If their environment changes to have only large rocks, which of the following guppy populations will most likely survive?

• Only Population 2 will survive because it is the only population with variation.

• All the populations will survive because the guppies will change the size of their spots if they need to.

• Populations 1 and 2 will most likely survive.

• Populations 2 and 3 will most likely survive.

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Harbor seals live in northern oceans and have a layer of blubber (fat) that keeps them warm. Seals can have blubber of different thicknesses. Seals with thicker blubber are more likely to stay warm and survive in cold ocean waters. But, in warm ocean waters, thicker blubber can make the seals overheat and die. The population of seals once lived in an environment where the water was cold. The image shows what the population looked like then. The environment changed and now the water is very warm. What do you think is more likely and why?

• The seals will all die.

• The seals might evolve to have less blubber with a mutation .

• There will be more seals with thick blubber.

• There will be more seals with thin blubber.

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The population of seals once lived in an environment where the water was cold. The environment changed and now the water is very warm. What prediction best shows what the population could look like after many generations? What could have caused the change?

• Prediction 1 is best. Two seals with thick or medium blubber had a baby with a mutation in its genes for the thin trait. Because thin seals are more likely to survive, that baby survived long enough to pass on its mutation, so the thin trait became more common over generations.

• Prediction 1 is best. Seals with thin blubber are more likely to survive, so seals with thick and medium blubber began to have offspring with a mutation in its genes for the thin trait, so that their offspring would have a better chance to survive.

• Prediction 2 is best. A seal could have been born with a mutation in its genes for the thin trait and lived for a little while, but it would have been more likely to die before it had any offspring, so the final population will only have seals with thick or medium blubber.

• Prediction 2 is best. A seal could have been born with a mutation in its genes for the thin 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 seals with thick or medium blubber.

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Barrel cactuses live in the Mexican desert. They are covered in sharp spines. Cactuses can have spines of different lengths. Their sharp spines help protect them from being eaten by bighorn sheep. Cactuses with longer spines are less likely to be eaten by the sheep. The diagrams below show three possible cactus populations. their environment changes to have many bighorn sheep, which of the following cactus populations will most likely survive?

• Populations 1 and 2 will most likely survive.

• Populations 2 and 3 will most likely survive.

• Only Population 2 will survive because it is the only population with variation.

• All the populations will survive because the cactuses will change the length of their spines if they need to.

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Guppies are small fish that live in South American rivers. They can have large spots, medium spots, or small spots. The river bottoms are covered in rocks. Guppies with spots that are the same size as the rocks on the bottom are harder for bigger fish to see and catch. The population of guppies shown lives in an environment that has always had large rocks. Could there ever have been guppies with small spots in this population?

• No guppies could have been born with the small-spot trait because none of the adult guppies had that trait to pass down.

• No guppies could have been born with the small-spot trait in the past, but some with that trait could be born in the future if the environment changes to have small rocks.

• A baby guppy could have been born with genes for the mutant small-spot trait and lived for a little while, but it would have died before it had any offspring.

• A baby guppy could have been born with genes for the mutant small-spot trait, but its mutant trait would have caused it to die when it was born.

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Eider ducks live in the ocean and have a layer of warm feathers underneath their regular feathers. They can have feathers of different thicknesses. These feathers help the ducks stay warm in cold water. Ducks with thicker feathers are more likely to stay warm and survive in cold water. But, in warm water, thicker feathers can make the ducks overheat and die. their environment changes to have very cold water, which of the following duck populations will most likely survive?

• Populations 1 and 2 will most likely survive.

• Populations 2 and 3 will most likely survive.

• Only Population 2 will survive because it is the only population with variation.

• All the populations will survive because the ducks will change their feather thickness if they need to.

Tags

NGSS.MS-LS4-4

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Blue jays are birds that live in the forest. They can have beaks of different thicknesses. Blue jays use their beaks to get to the seeds they eat. Blue jays with thinner beaks can easily reach and eat the seeds inside pinecones. Blue jays with thicker beaks can easily open and eat seeds with hard shells. The diagram below shows a population of blue jays that live in a forest. At time 1, the population had the same number of blue jays with thick beaks and blue jays with thin beaks. At time 2, after many generations, there were many more blue jays with thin beaks and fewer jays with thick beaks in the population. did the environment change between time 1 and time 2? How did the population change?

• There were more trees that had pinecones with seeds. With each generation, more blue jays with thin beaks survived long enough to pass on the gene for thin beaks to their offspring.

• There were more trees that had pinecones with seeds. Blue jays with thin beaks are more likely to survive, so the blue jays with thick beaks changed to have thin beaks.

• There were more trees that had pinecones with seeds. Blue jays with thin beaks are more likely to survive, so both kinds of blue jays passed on the gene for thin beaks to their offspring.

• You cannot tell how the environment changed. With each generation, more blue jays passed on the gene for thin beaks to their offspring.

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