Question 1

Which process is the primary entry point for energy into most terrestrial ecosystems?

Accepted Answer

Photosynthesis

Question 2

What is the key event in photosynthesis that allows sunlight energy to be stored in organic molecules?

Accepted Answer

Carbon fixation

Question 3

Gross Primary Production (GPP) in an ecosystem is best defined as:

Accepted Answer

The total amount of carbon fixed by all autotrophs

Question 4

Which equation correctly represents the relationship between Net Primary Production (NPP), Gross Primary Production (GPP), and Respiration?

Accepted Answer

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

Question 5

Which of the following nutrients is typically limiting in terrestrial habitats, thus constraining NPP?

Accepted Answer

Nitrogen

Question 6

A lake with low phosphorous levels, clear water, and high oxygen content is best described as:

Accepted Answer

Oligotrophic

Question 7

What is the most likely consequence of adding excess phosphates to a freshwater lake?

Accepted Answer

Increase in algal growth and decrease in oxygen

Question 8

Eutrophication is primarily caused by which of the following?

Accepted Answer

Enrichment of water with dissolved nutrients such as phosphates

Question 9

Which of the following is a major source of phosphates that can lead to eutrophication?

Accepted Answer

Detergents containing sodium tripolyphosphate (STPP)

Question 10

What is the primary effect of eutrophication on aquatic animal life?

Accepted Answer

Depletion of dissolved oxygen and death of animal life

Question 11

Which trophic level consists of organisms that feed on dead and decomposing material?

Accepted Answer

Detritivores

Question 12

In a food chain, which organism is most likely to be a tertiary consumer?

Accepted Answer

Snake

Question 13

Which of the following best describes a food web?

Accepted Answer

A complex network of feeding relationships among organisms in an ecosystem

Question 14

Which aquatic ecosystem has the highest average net primary productivity according to the provided data?

Accepted Answer

Estuaries

Question 15

What is the main reason dead zones form near river deltas such as the Mississippi River Delta?

Accepted Answer

Excess input of phosphates and nitrates from agricultural runoff

Question 16

Which of the following is a correct multi-step application of the NPP equation? If an ecosystem has a GPP of 1000 kcal/m$$^2/yr $$and autotroph respiration is 400 kcal/m$$^2/yr$$, what is the NPP?

Accepted Answer

$$\mathrm{NPP} = 1000 - 400 = 600$$ kcal/m$$^2/yr$$

Question 17

Which limiting nutrient is most likely to constrain NPP in the open ocean?

Accepted Answer

Iron

Question 18

Why did the federal government ban phosphates in detergents in 1993?

Accepted Answer

To prevent eutrophication and protect aquatic ecosystems

Question 19

Which of the following scenarios would most likely result in an increase in oxygen-poor water and fish kills?

Accepted Answer

A lake receiving runoff from fertilized lawns and farms

Question 20

Which of the following best explains why energy transfer between trophic levels is inefficient?

Accepted Answer

Most energy is lost as heat during cellular respiration

Ecosystem Energy Flow, Productivity, and Trophic Interactions

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