Question 1

Which of the following best describes the difference between energy flow and chemical cycling in an ecosystem?

Accepted Answer

Energy flows in one direction through the ecosystem, while chemicals cycle within the ecosystem.

Question 2

Which group of organisms is primarily responsible for returning chemical elements from dead organic matter to the soil in an ecosystem?

Accepted Answer

Decomposers

Question 3

What is the correct equation for net primary production (NPP) in an ecosystem?

Accepted Answer

$$\mathrm{NPP} = \mathrm{GPP} - \mathrm{Ra}$$

Question 4

A scientist adds ammonium to several marine water samples and observes a dramatic increase in phytoplankton density. What does this result suggest?

Accepted Answer

Phytoplankton growth is limited by ammonium availability.

Question 5

Which of the following best explains why energy transfer between trophic levels is typically only about 10% efficient?

Accepted Answer

Most energy is used for cellular respiration or lost as heat.

Question 6

Which process in the nitrogen cycle converts atmospheric $$\mathrm{N}_2$$ into a form usable by plants?

Accepted Answer

Nitrogen fixation

Question 7

A field experiment shows that adding both nitrogen and phosphorus, along with iron, greatly increases phytoplankton primary production in the Sargasso Sea. What does this indicate about the ecosystem?

Accepted Answer

Nitrogen, phosphorus, and iron are all limiting nutrients.

Question 8

Which of the following is an example of biological augmentation in restoration ecology?

Accepted Answer

Planting nitrogen-fixing plants to improve soil fertility

Question 9

Which of the following statements about the law of conservation of mass is correct in the context of ecosystems?

Accepted Answer

Matter is continually recycled within ecosystems.

Question 10

Which of the following would most likely increase net primary production (NPP) in a terrestrial ecosystem?

Accepted Answer

Increasing temperature and moisture

Question 11

In the water cycle, which process directly returns water from plants to the atmosphere?

Accepted Answer

Evapotranspiration

Question 12

Which of the following best describes the role of decomposers in the carbon cycle?

Accepted Answer

They break down dead organisms, releasing CO$$_2$$ through respiration.

Question 13

A grassland receives 1,000,000 J of sunlight. If the energy transfer efficiency between trophic levels is 10%, how much energy is available to secondary consumers?

Accepted Answer

$$100\ \mathrm{J}$$

Question 14

Which of the following is a key difference between primary and secondary production in an ecosystem?

Accepted Answer

Primary production is the energy stored by autotrophs; secondary production is the energy stored by heterotrophs.

Question 15

Which process in the phosphorus cycle makes phosphate available to plants?

Accepted Answer

Weathering of rocks

Question 16

Which of the following is an example of bioremediation?

Accepted Answer

Using bacteria to break down oil spills in the ocean

Question 17

Why do birds and mammals typically have lower production efficiencies compared to insects and fish?

Accepted Answer

They use more energy maintaining a constant body temperature.

Question 18

Which of the following best explains why tropical rain forests have high net primary production?

Accepted Answer

They have high levels of precipitation and warm temperatures.

Question 19

Which of the following is a real-world consequence of eutrophication in aquatic ecosystems?

Accepted Answer

Algal blooms followed by oxygen depletion and fish kills

Question 20

Which of the following best describes the role of autotrophs in an ecosystem?

Accepted Answer

They convert inorganic molecules into organic molecules using energy from sunlight or inorganic compounds.

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