Chapter 3 Population and Resources Amplify

A population of tigers lives in Bangladesh. Over 50 years, the size of the tiger population increased. What best explains the increase in the size of the tiger population?

• A lot of tigers were born and none of them died.

• Fewer tigers were born than died.

• The tiger population is always increasing because no animal eats tigers.

• More tigers were born than died.

Scientists have been studying the size of three populations in a grassland. In this ecosystem, lizards eat fireflies, and fireflies eat gnats (a type of insect). The data showed that all three populations were stable. Then the lizard population decreased suddenly. What will most likely happen to the size of the firefly population as a result?

The firefly population will . . .

• increase because there are less lizards eating them.

• decrease because there are more lizards eating them.

• stay the same

• increase because there will be more energy storage molecules available for the fireflies to eat.

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In Australia, both opossums and foxes eat rats. The sizes of the populations have been stable for the last 12 years, but recently the size of the opossum population increased. What will likely happen to the fox population?

The size of the fox population will . . .

• increase because there will be more rats to make energy.

• decrease because the opossum population is taking more energy storage molecules from the rats.

• stay the same because there are still energy storage molecules available.

• decrease because the opossum population is using the fox population for energy storage molecules.

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A population of bluefish lives in the Gulf of Mexico. Over the last 50 years, the size of the bluefish population has decreased. What best explains the decrease in the size of the bluefish population?

• A lot of bluefish died and no new bluefish were born.

• Fewer bluefish were born than died.

• More bluefish were born than died.

• The bluefish population is always decreasing because bluefish are always being eaten.

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Scientists have been studying the size of three populations in a region. In this ecosystem, lions eat wild pigs, and wild pigs eat frogs. The data showed that all three populations were stable. Then the frog population decreased suddenly. What will likely happen to the size of the wild pig population as a result?

The size of the wild pig population will . . .

• increase because the wild pigs and lions will find energy storage molecules elsewhere.

• decrease because there are less energy storage molecules available.

• stay the same because the lions are still stable.

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In the Arctic Ocean, sharks eat whales, and whales eat crabs. In the last 10 years, the sizes of the populations have been stable, but recently the size of the crab population increased. What will likely happen to the shark population?

The size of the shark population will . . .

• increase

• decrease

• stay the same

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A large population of ducks lives in an area with a lake. In the last 40 years, the size of the duck population has stayed the same. What must be true about the duck population during the last 40 years?

• The number of ducks that were born was the same as the number of ducks that died.

• Humans started protecting the duck population so they stopped dying.

• No ducks were born and no ducks died.

• The ducks did not have any baby ducks during these years.

Scientists have been studying the size of three populations in a swampland. In this ecosystem, herons (a type of bird) eat frogs, and frogs eat dragonflies. The data showed that all three populations were stable. Then the dragonfly population increased suddenly. What will likely happen to the frog population as a result?

The size of the frog population will . . .

• increase

• decrease

• stay the same

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In North America, both bears and eagles eat trout. The sizes of the populations have been stable for the last 9 years, but recently the size of the eagle population decreased. What will likely happen to the bear population?

The size of the bear population will . . .

• increase

• decrease

• stay the same

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A population of mice lives in the northeastern United States. Over the last 50 years, the size of the mouse population decreased. What best explains the decrease in the size of the mouse population?

• Fewer mice were born than died.

• More mice were born than died.

• A lot of mice died and no new mice were born.

• The mouse population is always decreasing because mice are always being eaten.

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