1 In an ecosystem, what happens to the atoms of certain chemical elements such as carbon, oxygen, and nitrogen?

(1) They move into and out of living systems.
(2) They are never found in living systems.
(3) They move out of living systems and never return.
(4) They move into living systems and remain there.

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2 The diagram below shows the relationships between the organisms in and around a pond

One additional biotic factor needed to make this a stable ecosystem is the presence of

(1) producers         (3) decomposers
(2) herbivores        (4) consumers

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3 What is the major environmental factor limiting the numbers of autotrophs at great depths in the ocean?

(1) type of seafloor
(2) amount of light
(3) availability of minerals
(4) absence of biotic factors 

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4 The diagram below shows a food chain.

If the population of bobcats decreases, what will most likely be the long-term effect on the rabbit population?

(1) It will increase, only.
(2) It will decrease, only.
(3) It will increase and then decrease.
(4) It will decrease and then increase.

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5 An owl cannot entirely digest the animals upon which it preys. Therefore, each day it expels from its mouth a pellet composed of materials such as fur, bones, and cartilage. By examining owl pellets, ecologists are able to determine the

(1) autotrophs that owls prefer
(2) organisms that feed on owls
(3) pathogens that affect owls
(4) consumers that owls prefer

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