Eoc Food Chain and Food Web

The diagram shows a simplified marine food web in the northern Pacific Ocean. Humans started fishing for many of the deep-sea fish, causing their population to decrease. This caused the seal population in the area to decrease. What effect would these changes most likely have on the near-shore fish population?

• The near-shore fish population would not be affected by a change in the deep-sea fish population, because these communities are too far apart.

• The near-shore fish population would eventually decrease because orcas eating more sea otters would allow sea urchins to eat too much kelp.

• The near-shore fish population would eventually increase because they no longer have to compete with as many deep-sea fish for food.

• The near-shore fish population would increase as more sea otters were eaten because more sea urchins would be available as food.

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Crawfish are one of the many invertebrates in this lake food web. Given the information in this food web, which change would most likely cause an increase in the crawfish population in the lake?

• removing carp

• removing bass

• adding sunfish

• adding carp

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After being gone for many years, wolves were reintroduced into Yellowstone National Park in 1995. Given the information in the food web, which species likely benefited the most from the return of the wolves?

• deer

• gopher

• grasses

• aspens

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The diagram shows a food chain for a forest ecosystem. Given the relationships shown by the food chain, which statement is most likely true about the trees, insects, and birds living in the forest?

• The total mass of insects is about ten times the total mass of birds.

• The total number of trees is about ten times the total number of insects.

• There are about ten times as many species of trees as there are species of insects.

• The energy in bird bodies is about ten times more concentrated than the energy in insect bodies.

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The diagram shows trophic levels in an ecosystem, with the energy content at each level labeled. Which statement correctly explains why each trophic level has less energy than the one below it?

• Much of the energy within a trophic level is used for life processes and is not stored.

• When organisms increase their body size, they convert energy to additional mass.

• Body mass tends to decrease with trophic level, so energy demands are lower in each successive trophic level.

• Organisms at higher trophic levels use energy more efficiently.

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Biomass is the amount of matter at each trophic level in an ecosystem. Although the energy pyramid for this ocean ecosystem is normal, the biomass pyramid shows an inversion near the bottom. Which statement best explains how there can be fewer phytoplankton than zooplankton?

• The phytoplankton have less energy than the zooplankton.

• The phytoplankton grow and reproduce very rapidly.

• The phytoplankton depend on sunlight to make their own food.

• The phytoplankton are eaten by organisms at all trophic levels.

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The largest animals on Earth are the baleen whales. They feed primarily on krill, a small, shrimp-like animal. What is the advantage to baleen whales in eating tiny first-order consumers rather than eating large animals that are third- or fourth-order consumers?

• The tiny first-order consumers are less dangerous than animals of higher orders.

• The total amount of available energy is greater in first-order consumers than in higher orders.

• The first-order consumers tend to be more spread out than higher-order consumers.

• The number of available producers is greater for lower orders.

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In a marine ecosystem, a fish eats plankton and is then eaten by a dolphin. Which statement best describes the energy flow through this process?

• Most of the energy from the plankton is passed on to the dolphin, but about ten percent of the energy is lost.

• About half of the energy from the plankton is lost through feces, and the other half is passed on to the dolphin.

• Most of the energy from the plankton is converted to heat, and only a small amount is passed on to the dolphin.

• The energy from the plankton becomes about ten times more concentrated in the fish and concentrates again in the dolphin.

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In aquatic ecosystems, phytoplankton provide the energy for most food webs. Which organisms generally fulfill the same role in terrestrial ecosystems?

• fungi

• bacteria

• plants

• animals

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A farming community has the food web shown. A state agency wants to spray insecticides widely to control a particular insect pest that has been damaging crops. Which populations will be most at risk as a result of such an action?

• birds and insectivorous rodents

• birds and snakes

• plants and insectivorous rodents

• plants and herbivorous rodents

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