Population Change

If the number of births in a population is the same as the number of deaths in a population, what will happen to the growth of the population?

• It will increase.

• It will decrease.

• It will stay the same.

• It will fluctuate.

The graph shows a population of moths from 2008 - 2017. From 2009 - 2012, the number of moths changed from 30 to 325. Which factor could have caused this increase in population?

• Increase in predators

• Increase in disease in moths

• Increase in habitat

• Decrease in food

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Foxes are predators of hares. When the population of hares increases, soon after what happens to the population of foxes?

• It increases.

• It decreases.

• It stays the same.

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What happens to the prey population if the predator population increases?

• The prey population increases

• The prey population decreases

• The prey population stays the same

• The prey population migrates

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What is the effect of an increase in prey population on the predator population?

• The predator population decreases

• The predator population increases

• The predator population stays the same

• The predator population migrates

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How do changes in abiotic factors like temperature and rainfall affect the populations of organisms in the rainforest?

• They have no effect on populations

• They only affect plant populations

• They can cause populations to increase or decrease

• They only affect animal populations

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Analyze the relationship between predator and prey populations in an ecosystem.

• Predator populations always increase when prey populations decrease.

• Predator and prey populations are independent of each other.

• Predator populations increase when prey populations increase, and decrease when prey populations decrease.

• Prey populations increase when predator populations increase.

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DOK Level 3: Strategic Thinking

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 less food 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 less food available in the ecosystem for the worm population, so there will be fewer births in the worm population.

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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. Less food 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 food available in the ecosystem for the anteater population, so there will be more births in the anteater population.

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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?

• 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 less food so there will be more food 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 less food 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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