Trophic Cascades and Keystone Species

Human population growth has led to a reduction in the populations of predators throughout natural ecosystems across the united states. Scientists consider the loss of these predators to have a

• positive effect, because an increase in their prey helps to maintain stability in the ecosystem

• positive effect, because predators usually eliminate the species they prey on

• negative effect, since predators have always made up a large portion of our food supply

• negative effect, because predators have an important role in maintaining stable ecosystems

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Why are bees considered a keystone species?

• The honey they make supports the bear population

• They pollinate flowers that produce fruit which supports the ecosystem

• They sting when threatened

• They live in hives

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Why are some sharks considered a keystone species?

• Because they are a top predator

• They scare off smaller fish that may overgraze an area of sea grass

• They are tertiary consumers

• They are cartilaginous

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According to the graph, what is causing the deer population to decrease

• They got sick

• The wolf population is decreasing

• The wolf population increased

• They ran out of food

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Why do the sea anemones have a negative impact on the Kelp population?

• The sea anemones eat the predators of the kelp

• The sea anemones eat the otters

• The sea anemones protect the kelp

• The sea anemones eat the kelp

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Why do the otters have a positive affect of the kelp?

• The otters eat the kelp

• The eat the sea anemones that eat the kelp - less sea anemones means more kelp

• The otters eat the sea anemones and when their population increases the kelp population increases

• The otters help the kelp get nutrients

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Why do the seabirds positively impact the soil nutrients

• the less seabirds the more soil nutrients

• the more seabirds the more soil nutrients

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If you removed the Rinderpest virus - what would happen to the other populations?

• The wildebeest population would increase

• The vegetation population would decrease due to Wildebeest populations

• There would be less fires because the vegetation population decreased.

• All of these would impacts

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How do the predators have a positive impact on the vegetation?

• Since the predators eat the herbivores they eat the producers

• Since the predators eat the herbivores and keep that population in check so they do not over eat the vegetation

• The predators do not eat the vegetation so it is a positive impact

• The predators eat the vegetation keeping it in control

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Which of the following describes the broader consequences or side-effects when a certain species that usually helps to keep the entire ecosystem balanced is reduced or removed.

• trophic level

• trophic cascade

• food web

• keystone species

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