Populations and Resources

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?

• 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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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?

• 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 leads 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?

• 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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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?

• 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?

• 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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The data showed that all three populations were stable. Then the snail population increased suddenly. What will likely happen to the size of the perch population as a result?

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

• increase. The larger snail population will provide more energy storage molecules for the perch population, so they will reproduce more. This will lead to more births than deaths in the perch population.

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

• decrease. The larger snail population will take more energy storage molecules from the ecosystem, leaving fewer available for the perch population. This will lead to more deaths than births in the perch population.

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In a rainforest, both spiders and frogs eat flies. The sizes of the populations have been stable for the last 10 years, but recently the size of the frog population decreased. What will likely happen to the spider population?

• increase. The smaller frog population will leave more energy storage molecules for all other populations in the ecosystem, so all populations will reproduce more. This will lead to more births in the spider population.

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

• stay the same. Frogs and spiders do not eat each other, so the number of births and deaths in the spider population will stay the same.

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

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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.

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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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.