Question 1

Which statement best explains why energy transfer between trophic levels in an ecosystem is inefficient?

Accepted Answer

Energy is lost as heat and molecular waste during metabolic processes, so only about 10% is transferred to the next trophic level.

Question 2

A forest ecosystem has a gross primary productivity (GPP) of $$12,000\ \mathrm{$$kcal/m^2$$/year}$$ and the energy used for respiration (R) is $$7,000\ \mathrm{$$kcal/m^2$$/year}. $$What is the net primary productivity (NPP) of this ecosystem?

Accepted Answer

$$NPP = GPP - R = 5,000\ \mathrm{$$kcal/m^2$$/year}$$

Question 3

Which of the following best describes the role of decomposers in nutrient cycling within ecosystems?

Accepted Answer

Decomposers break down organic matter, releasing nutrients back into abiotic reservoirs for reuse by producers.

Question 4

Which process is primarily responsible for moving carbon from the atmosphere into the biotic reservoir of an ecosystem?

Accepted Answer

Photosynthesis by autotrophic organisms

Question 5

A lake receives excess nitrogen and phosphorus from agricultural runoff. What is the most likely ecological consequence?

Accepted Answer

Eutrophication, leading to algal blooms and aquatic dead zones

Question 6

Which equation correctly represents the relationship between gross primary productivity (GPP), respiration (R), and net primary productivity (NPP)?

Accepted Answer

$$NPP = GPP - R$$

Question 7

Why does biomagnification occur at higher trophic levels in a food web?

Accepted Answer

Certain toxins are not metabolized or excreted, so they accumulate in organisms and become more concentrated at higher trophic levels.

Question 8

Which human activity has most directly increased the concentration of atmospheric carbon dioxide ($$CO_2) in $$recent decades?

Accepted Answer

Burning fossil fuels and deforestation

Question 9

In a terrestrial ecosystem, what is the primary source of phosphorus for plants?

Accepted Answer

Weathering of rocks and minerals

Question 10

If humans shift from a diet based on secondary consumers (meat) to one based on primary producers (plants), what is the most likely ecological outcome?

Accepted Answer

More humans can be supported because energy transfer is more efficient at lower trophic levels.

Question 11

Which of the following is a direct effect of increased atmospheric $$CO_2 on $$global climate?

Accepted Answer

Enhanced greenhouse effect leading to global warming

Question 12

Which statement best describes the difference between energy flow and nutrient cycling in ecosystems?

Accepted Answer

Energy flows in one direction and is eventually lost as heat, while nutrients cycle between biotic and abiotic reservoirs.

Question 13

Which of the following is a density-dependent constraint on trophic levels in an ecosystem?

Accepted Answer

The reduction in population size that can be supported as trophic levels increase due to energy loss at each level

Question 14

Which process is responsible for converting atmospheric nitrogen ($$N_2) $$into a biologically usable form for plants?

Accepted Answer

Nitrogen fixation by bacteria

Question 15

A tropical rainforest has high moisture and high temperature. What is the expected effect on the rate of decomposition and detritus accumulation?

Accepted Answer

High rate of decomposition and little to no detritus accumulation

Question 16

Which of the following best explains why the water cycle is crucial for ecosystem diversity?

Accepted Answer

It contributes to the storage and movement of dissolved nutrients, affecting biodiversity.

Question 17

Which of the following is NOT a predicted effect of global climate change on biodiversity?

Accepted Answer

Complete elimination of nutrient cycling in ecosystems

Question 18

Which of the following is a major abiotic reservoir for nitrogen in the global biogeochemical cycle?

Accepted Answer

Atmosphere as $$N_2$$

Question 19

A city replaces a large forested area with concrete buildings. What is the most likely impact on the local water cycle?

Accepted Answer

Decreased percolation and increased surface runoff, leading to nutrient loss

Question 20

Which of the following is a correct statement about the greenhouse effect?

Accepted Answer

It is caused by the trapping of heat from solar irradiation by atmospheric compounds such as $$CO_2$$, $$CH_4$$, and $$N_2O.$$

Energy Flow, Nutrient Cycling, and Ecosystem Ecology: Study Notes

Guida di studio - Domande di pratica

Study guide - Flashcard