Natural Selection

The process by which the distribution of traits in a population changes over many generations

• Natural Selection

• Adaptive Trait

• Extinct

• Gene

• Mutation

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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 diagrams below show three possible hummingbird populations.

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

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

• Populations 1 and 2 will survive.

• Populations 2 and 3 will survive.

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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.The diagram below shows a population of ducks that live in an area of an ocean. Based on the change to the population, how did the environment change?

• The water became warm and the ducks with thick feathers changed to have thin feathers.

• The water became warm and since ducks with thin feathers were more likely to survive, both kinds of ducks passed on the gene for thin feathers to their offspring.

• The water became warm and with each generation, more ducks with thin feathers survived long enough to pass on the gene for thin feathers to their offspring.

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There is a kind of snake that can be born with red or yellow skin. Eagles hunt these snakes, but snakes that are the same color as their environment are harder for the eagles to see and catch. The diagram below shows a population of snakes that live in an environment where there was yellow sand and red dirt. At time 1, the population had the same number of yellow and red snakes. At time 2, after many generations, there were many more red snakes and fewer yellow snakes in the population. How did the environment change between time 1 and time 2? How did the population change?

• You cannot tell how the environment changed. With each generation, more snakes passed on the gene for red skin to their offspring.

• There was more red dirt in the environment so with each generation, more red snakes survived long enough to pass on the gene for red skin to their offspring.

• There was more red dirt in the environment and since red snakes are more likely to survive, the yellow snakes changed to have red skin.

• There was more red dirt in the environment and since red snakes are more likely to survive, so both kinds of snakes passed on the gene for red skin to their offspring.

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Process by which individuals that are better suited to their environment survive and reproduce most successfully; also called natural selection. (a)  

• Survival of the Fittest

• Extinction

• Derived trait

• Artificial Selection

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The mechanism that causes evolution is ​ (a)   .

• natural selection

• biogeography

• vestigial structures

• homologous structures

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One mechanism that causes evolution is ​ (a)   .

• natural selection

• biogeography

• vestigial structures

• homologous structures

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Seals with thicker blubber (fat) 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 diagrams below show three possible seal populations. If their environment changes to have warm water, which of the following seal 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 seals will change the thickness of their blubber if they need to.

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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. How did the environment change between time 1 and time 2? How did the population change?

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

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

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

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Lizards with shorter legs are better at climbing trees than lizards with longer legs. This makes lizards with shorter legs better at escaping from the floods that sometimes cover the islands. The diagram below shows a population of lizards that live on an island. How did the environment change between time 1 and time 2? How did the population change?

• You cannot tell how the environment changed. With each generation, more lizards passed on the gene for short legs to their offspring.

• There were more floods. Lizards with short legs are more likely to survive, so the lizards with long legs changed to have short legs.

• There were more floods. Lizards with short legs are more likely to survive, so both kinds of lizards passed on the gene for short legs to their offspring.

• There were more floods. With each generation, more lizards with short legs survived long enough to pass on the gene for short legs to their offspring.

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