When do biologists consider two populations to be separate species?

• The populations have three different traits.

• The populations no longer produce offspring together.

• The organisms are different colors.

A volcano erupts on an island. Only a few of the original palm trees survived the lava.

This random event caused the palm trees to lose most of their genetic diversity.

What is this called?

• natural selection

• genetic drift

• adaptive radiation

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Bald eagles live in the forests of North America near open water. They hunt fish.

Harpy eagles live in Central and South American rainforests where they hunt small prey.

Both are large bird species that act as predators in their environment but they look and behave very differently.

Which answer best explain why these eagles are so different from each other?

• The two environments changed so that each eagle species could survive more successfully.

• The two species live in different environments so natural selection favored the best traits in those environments.

• The two species chose to evolve new traits to match their different environments.

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True or False: The formation of new species is called speciation.

• Yes

• No

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Match each example on the left to the type of reproductive barrier on the right.

• physical barrier

• The reproductive parts of a fly and a bee are not compatible.

• behavioral barrier

• Female spring peeper frogs only mate with males that make a specific sound.

• geographic barrier

• A desert keeps frogs on either side from mating with one another.

Examine the diagram.

Hawaiian honeycreepers are a group of birds all descended from a common ancestor. Their populations all evolved different beak shapes according to the food they eat.

What term best describes how Hawaiian honeycreepers evolved?

• adaptive radiation

• genetic drift

• bottleneck effect

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Thousands of years ago, a small population of humans moved to the island of Ireland. One of those people had the gene for red hair. Now red hair is extremely common in Ireland even though it is rare in the rest of the world.

Which term best describes how red hair became common in Ireland?

• founder effect

• speciation

• coevolution

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The California condor is a bird of prey. In 1987, only 27 California condors were alive. Zoos used breeding programs to raise their population. However, the condors lost most of their genetic diversity.

What word best describes what happened to the gene pool of the California condors?

• adaptive radiation

• bottleneck effect

• coevolution

Saguaro cacti have deep flowers that bloom for only one night in late spring.

Lesser long-nosed bats have noses and tongues that are shaped perfectly for getting nectar from the flowers.

The bats also collect pollen on their bodies when moving from flower to flower.

What word best describes the relationship between the cactus and the bat?

• speciation

• genetic drift

• coevolution

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