Ecosystems and Population Change

Hawaii has many active volcanoes as a result of a hotspot on the ocean floor. The Loihi seamount is currently underwater and with continued volcanism, a new island is expected to form. How will succession impact the species diversity and populations of Loihi? Select all that apply.

• Primary succession will cause an increase in both producer and consumer populations.

• Primary succession will cause species diversity to increase.

• Secondary succession will cause a decrease in both producer and consumer populations.

• Primary succession will cause an increase in producer populations, but a decrease in consumer populations.

• Secondary succession will cause species diversity to decrease.

Suppose you are an ecologist investigating an ecosystem after a devastating natural event occurs. The area previously had been inhabited. Now, the environment has lost all animal species, as well as most plant species. How will succession take place and what impact will it have? Choose two correct answers.

• A. Secondary succession will restart from the existing soil, nutrients, and plant species in the ecosystem; plant diversity will increase.

• B. Secondary succession will restart from the existing plant species in the ecosystem but plant diversity will decrease.

• C. Since plant species diversity decreases, animals that depend on the plant species will leave the ecosystem to recover elsewhere.

• D. Once plant species diversity increases, animal populations that depend on the plant species will begin to recover.

• E. Primary succession will restart from the existing soil, nutrients, and plant species in the ecosystem; plant diversity will increase.

Which options describe how L. pulchella impacts energy transfer and biodiversity throughout the marine ecosystem? Choose two correct answers.

• A. L. pulchella will not have predators in the new environment, therefore they can grow without limit and compete against native species. This will decrease biodiversity and disrupt energy transfers in the food web.

• B. L. pulchella will cause a decrease in the clam population, which will cause an increase in the algae population. This will decrease biodiversity and disrupt energy transfers in the food web.

• C. L. pulchella will not have prey in the new environment so they will be able to compete against other species. The clam population will also increase and compete with the native species. Biodiversity will increase.

• D. L. pulchella will not have predators in the new environment so they can grow without limit and compete against native species. This will increase biodiversity and increase energy transfer in the food web.

The image shows an Amazon rainforest food web. Which of the following best describes the relationships between the organisms shown in the food web?

• Predator-prey relationships

• Symbiotic relationships

• Competitive relationships

• Parasitic relationships

How will a toucan being overhunted affect the transfer of energy in the food web? Choose the best response.

• Overhunting toucans will only affect the boa constrictor and sloth populations because their food energy sources will increase. This will also increase the producer population.

• Overhunting toucans will only affect the toucan and the boa constrictor. The boa constrictor will no longer have a main food energy source, and both populations will continue to decrease.

• Overhunting toucans will only affect the toucan and the sloth. The sloth will not have the food to eat, causing a decrease in food energy for the sloth.

• Overhunting toucans will affect the entire food web. Boa constrictors will rely more heavily on sloths as a main food energy source, causing a decrease in the sloth population. Producers may increase as a result.

How do primary and secondary succession affect species diversity after ecosystems are disrupted by human activity?

• Primary and secondary succession both cause an increase in species diversity, therefore making the ecosystem more stable.

• Primary and secondary succession both cause a decrease in species diversity, therefore making the ecosystem less stable.

• Primary and secondary succession both cause an increase in species diversity, therefore making the ecosystem less stable.

• Primary succession causes an increase in species diversity, and secondary succession causes a decrease in species diversity.

After a forest fire in Yellowstone National Park in 1988, 793,880 acres of land burned and a large population of plant and animal life was affected but not entirely destroyed. The lodgepole pine populations, a producer that the elk feed on, came back quickly. The wheatgrass populations, a producer that the pronghorn feed on, took longer to repopulate. Which statement is true based on the information?

• This is an example of primary succession. Producer populations slowly decreased overall except for the lodgepole pine and wheatgrass populations. As these producer populations increased, elk and pronghorn populations also increased.

• This is an example of secondary succession. The elk and pronghorn populations quickly increased because their return is not dependent on the producer populations they feed on.

• This is an example of primary succession. The elk and pronghorn populations decreased as the lodgepole pine and wheatgrass populations increased. New species then started to repopulate the area.

• This is an example of secondary succession. The elk population increased as the lodgepole pine population increased. The pronghorn population took longer to increase than the elk because the producer the elk feed on repopulated quicker.

An arctic food web is shown. Which organism is a keystone species in the food web?

• The whale, because it only eats zooplankton and is the largest animal within the food web

• The zooplankton, because all of its energy is transferred to the polar cod

• The polar bear, because it keeps the entire food web in balance

• The ocean algae, because it has the lowest amount of energy in the food web

If a flood occurred in this region and significantly reduced the zooplankton population, how could the food web be impacted?

• The loss of zooplankton could cause a decrease in the ocean algae population because the ocean algae would lose its only prey.

• The loss of zooplankton could cause a decrease in the polar bear population because there would be a decrease in the polar bear prey that feed on zooplankton.

• The loss of zooplankton could cause a decrease in the whale population because it is the only source of energy for whales.

• The loss of zooplankton could cause an increase in the polar cod population because there would be less competition for the polar cod.

Order the events based on how succession could occur after the landslide, from the first event to the final event.

Read the list of events.

1. A variety of vegetation grows.

2. The ecosystem is restored.

3. Lichens die and form healthy soil.

4. Lichens colonize bare rock.

5. Wildlife arrives and repopulates the area.

• 1, 3, 4, 5, 2

• 4, 2, 1, 5, 3

• 4, 3, 1, 5, 2

• 3, 1, 5, 4, 2