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.

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

• Fewer tigers were born than died.

• More tigers were born than died.

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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. The smaller lizard population will need fewer energy storage molecules (food) so they will eat fewer fireflies. This will lead to fewer deaths than births in the firefly population.

• increase. The smaller lizard population will leave more energy storage molecules available for the firefly population to reproduce more. This will lead to more births in the firefly population.

• stay the same. The size of the firefly resource population did not change, so the amount of energy storage molecules available for the fireflies did not change. There will be the same number of births and deaths in the firefly population.

• decrease. A decrease in any population causes a decrease in the sizes of all other populations in the ecosystem.

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1. A population of panthers lives in the southeastern United States. Over 50 years, the size of the panther population in the region increased. What best explains the increase in the size of the panther population?

• The panther population is always increasing because no animal eats panthers.

• Fewer panthers were born than died.

• More panthers were born than died.

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

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Scientists have been studying the size of three populations along the coast of Antarctica. In this ecosystem, penguins eat sardines (a type of small fish), and sardines eat zooplankton. The data showed that all three populations were stable. Then the penguin population decreased suddenly. What will likely happen to the size of the sardine population as a result?

• stay the same. The size of its resource population did not change, so the amount of energy storage molecules available for the sardines did not change. There will be the same number of births and deaths in the sardine population.

• decrease. A decrease in one population causes a decrease in the sizes of all other populations in the ecosystem.

• increase. The smaller penguin population will leave more energy storage molecules available for the sardine population to reproduce more. This will lead to more births in the sardine population.

• increase. The smaller penguin population will need fewer energy storage molecules, so they will eat fewer sardines. This will lead to fewer deaths than births in the sardine population.

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Scientists have been studying four populations in the ocean near Alaska. In the ocean, sharks eat sea otters, and both sea otters and sea stars eat clams.

The data shows that recently the shark population increased. How will the increase in the shark population affect the other populations? Be sure to explain whether the sea otter population, the sea star population, and the clam population will change, and why.

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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 . . .

• decrease. The larger crab population will leave fewer energy storage molecules available in the ecosystem for the shark population, so there would be fewer births in the shark population.

• increase. An increase in the size of any population leads to an increase in the sizes of all other populations in an ecosystem.

• increase. More energy storage molecules will be available to the shark population from the larger whale population, so the shark population will reproduce more. This will lead to more births than deaths in the shark population.

• stay the same. Sharks do not eat crabs, so the number of births and deaths in the shark population will 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.

• No ducks were born and no ducks died.

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

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

What do birds such as eagles and hawks need energy for?

• Flying

• Breathing

• Digesting food

• All of the above

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A population of deer lives in Canada. Over 50 years, the size of the deer population decreased. What best explains the decrease in the size of the deer population?

• A lot of deer died and no deer were born.

• Fewer deer were born than died.

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

• More deer were born than died.

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NGSS.MS-LS2-1

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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.

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

• More mice were born than died.

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

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