Chapter 3 Population and Resources

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.

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 (very small animals that live in water). 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? The size of the sardine population will . . .

• 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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In a mountain region, tigers eat wild pigs, and wild pigs eat worms. In the last 5 years, the sizes of the populations have been stable, but recently the tiger population has increased. What will likely happen to the worm population?

The worm population will . . .

• increase. The larger tiger population will lead to fewer wild pigs. The smaller wild pig population will need fewer energy storage molecules to reproduce, so they will eat fewer worms. This will lead to more births than deaths in the worm population.

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

• stay the same. Tigers do not eat worms, so the number of births and deaths in the worm population will stay the same.

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

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

• flying

• breathing

• digesting food

• all 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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Scientists have been studying the size of three populations in a grassland. In this ecosystem, hawks (a type of large bird) eat sparrows (a type of small bird), and sparrows eat seeds from buckwheat. The data showed that all three populations were stable. Then the hawk population increased suddenly. What will likely happen to the size of the sparrow population as a result?

The size of the sparrow population will . . .

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

• decrease. The larger hawk population will leave fewer energy storage molecules available for the sparrows, so the sparrow population will reproduce less. This will lead to fewer births in the sparrow population.

• decrease. The larger hawk population will need more energy storage molecules, so they will eat more sparrows. This will lead to more deaths than births in the sparrow population.

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

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In a rainforest, anteaters eat ants, and ants eat aphids (a type of very small insect). The sizes of the populations have been stable for the last 10 years, but recently the size of the aphid population decreased. What will likely happen to the anteater population?

The size of the anteater population will . . .

• stay the same. Anteaters do not eat aphids, so the number of births and deaths in the anteater population will stay the same.

• decrease. Fewer energy storage molecules will be available to the anteater population from the smaller ant population, so the anteater population will reproduce less. This will lead to fewer births than deaths in the anteater population.

• decrease. A decrease in the size of any population leads to a decrease in the sizes of all other populations in an ecosystem.

• increase. The smaller aphid population will leave more energy storage molecules available in the ecosystem for the anteater population, so there will be more births in the anteater population.

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A large population of squirrels lives in a forest. In the last 50 years, the size of the squirrel population has stayed the same. What must be true about the squirrel population during the last 50 years?

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

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

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

• No squirrels were born and no squirrels died.

Scientists have been studying the size of three populations in a grassland. In this ecosystem, snakes eat rats, and rats eat grasshoppers. The data showed that all three populations were stable. Then the grasshopper population decreased suddenly. What will likely happen to the size of the rat population as a result?

The size of the rat population will . . .

• stay the same. The size of their consumer population did not change, so the number of deaths in the rat population did not change. There will be the same number of births and deaths in the rat population.

• increase. The smaller grasshopper population will need fewer energy storage molecules so there will be more energy storage molecules available for the rat population to reproduce. This will lead to more births in the rat population.

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

• decrease. The smaller grasshopper population provides fewer energy storage molecules for the rat population, so the rat population will reproduce less. This will lead to fewer births than deaths in the rat population.

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In the northwestern United States, both coyotes and wolves eat deer. The sizes of the populations have been stable for the last 6 years, but recently the size of the wolf population increased. What will likely happen to the coyote population?

The size of the coyote population will . . .

• decrease. Fewer energy storage molecules will be available to the coyote population from the smaller deer population, so the coyote population will reproduce less. This will lead to fewer births than deaths in the coyote population.

• decrease. The larger wolf population will leave fewer energy storage molecules for all other populations in the ecosystem, so the coyote population will reproduce less. This will lead to fewer births in the coyote population.

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

• stay the same. Coyotes and wolves do not eat each other, so the number of births and deaths in the coyote population will stay the same.

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