Populations and Resources Amplify

Scientists have been studying the size of three populations in Peru. In this ecosystem, pumas (large wild cats) eat deer, and deer eat grass. The data showed that all three populations were stable. Then the puma population increased suddenly. What will most likely happen to the size of the deer 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 deer did not change. There will be the same number of births and deaths in the deer population.

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

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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 so they will eat fewer fireflies. This will lead to fewer deaths than births 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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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?

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

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

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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?

• decrease. The smaller frog population will provide fewer energy storage molecules for the wild pig population, so the wild pig population will reproduce less. This will lead to fewer births than deaths in the wild pig population.

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

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n 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. 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.

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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 . . .

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

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

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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. The smaller eagle 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 bear population.

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

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In an ecosystem, if the population of a primary consumer increases, what is the likely immediate effect on the population of the producers?

• A) The producer population will increase due to more energy storage molecules.

• B) The producer population will decrease due to increased consumption.

• C) The producer population will remain stable due to balanced energy flow.

• D) The producer population will fluctuate unpredictably.

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Which of the following best describes the concept of carrying capacity in an ecosystem?

• A) The maximum number of individuals in a population that the environment can support indefinitely.

• B) The minimum number of individuals needed to maintain a stable population.

• C) The average number of individuals in a population over a year.

• D) The total number of species an ecosystem can support.

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A scientist observes that a population of rabbits in a forest has suddenly decreased. Which of the following could be a plausible explanation?

• A) An increase in the rabbit's food supply.

• B) A decrease in the rabbit's predators.

• C) An outbreak of disease among the rabbits.

• D) A stable climate with no changes.

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