Question 1

You own 300 acres of patchy temperate forest mixed with grassy meadows. Which one of the following actions would increase the net primary productivity of the area the most?

Accepted Answer

Planting 500 new trees would increase the overall vegetation in the area, which would in turn increase the net primary productivity. Adding fertilizer may have a short-term increase in productivity, but it could also harm the ecosystem if overused. Introducing rabbits could lead to overgrazing and a decrease in productivity. Relocating deer could disrupt the entire food chain and lead to unintended consequences.

Question 2

Which of the following is an accurate statement regarding mineral nutrients in soils and their implication for primary productivity?

Accepted Answer

Phosphorous is often limiting to primary productivity, but in certain regions it may be abundant. However, it can become unavailable to plants due to leaching, which can occur in soils with high rainfall or irrigation. Adding a nonlimiting nutrient may not necessarily stimulate primary productivity if another nutrient is truly limiting. The productivity of soils also depends on a variety of factors beyond pH, such as nutrient cycling, soil structure, and the presence of organic matter.

Question 3

Many of the organisms in the ocean are nutrient-limited. If you wanted to investigate this phenomenon, one reasonable approach would be to ________.

Accepted Answer

Experimentally enriching some areas of the ocean and comparing their productivity to that of untreated areas would allow for a direct comparison of the effect of nutrient availability on productivity. Observing productivity from year to year or comparing nutrient concentrations between different zones or temperatures would not provide as direct of evidence for nutrient limitation.

Question 4

Which statement best describes what ultimately happens to the chemical energy that is consumed but not used to produce new biomass in the process of energy transfer between trophic levels in an ecosystem?

Accepted Answer

Energy not used in biomass production is eventually lost as heat due to cellular respiration, aligning with the second law of thermodynamics which states that energy transformations are not 100% efficient, leading to the dissipation of energy as heat.

Question 5

How is net ecosystem production (NEP)typically estimated in ecosystems?

Accepted Answer

Net ecosystem production (NEP) is typically estimated by measuring gas exchange from vegetation as well as estimates of respiration by all other organisms. This involves measuring the rate of carbon dioxide uptake during photosynthesis and the rate of carbon dioxide release during respiration. By subtracting respiration from photosynthesis, the net amount of carbon being stored or released by the ecosystem can be calculated, which is the NEP.

Question 6

How does inefficient transfer of energy among trophic levels result in the typically high endangerment status of many top-level predators?

Accepted Answer

Inefficient transfer of energy among trophic levels means that there is not enough energy being passed on to the top-level predators, which are typically carnivores. As a result, these predators have smaller populations that are more sparsely distributed. This makes them more vulnerable to habitat loss and other threats, which can result in their endangerment.

Question 7

Why is it that satellites, using wavelength reflectance technology, detect variable levels of productivity across Earth's oceans, rather than an increase toward the equator?

Accepted Answer

Productivity levels in Earth's open oceans can differ due to various factors such as depth, the presence of coral reefs, and ocean currents. These variations affect the amount of available nutrients and light for primary producers, leading to differences in productivity levels. Therefore, it is not necessarily a gradual increase toward the equator that is detected by satellites using wavelength reflectance technology.

Question 8

Use the following figure to answer the question.

After looking at the figure, what can be said about productivity in this ecosystem?

Accepted Answer

The answer of Use the following figure to answer the...

Question 9

What advantage would there be for an ecosystem ecologist to measure net ecosystem production (NEP)instead of net primary production (NPP)?

Accepted Answer

The answer of What advantage would there be for an...

Question 10

During a year, plants never use 100% of the incoming solar radiation for photosynthesis. What is a reasonable explanation for this?

Accepted Answer

Plants do not intercept all incoming light, as some light will strike water, bare soil, or rock.

Question 11

Which of the following is primarily responsible for limiting the number of trophic levels in most ecosystems?

Accepted Answer

The 10% rule states that only 10% of the energy available at one trophic level is transferred to the next level. This means that as energy is transferred up through the trophic levels, there is less and less energy available to support higher trophic levels. This ultimately limits the number of trophic levels that can exist in most ecosystems.

Question 12

Consider the food chain of grass → grasshopper → mouse → snake → hawk. About how much of the chemical energy fixed by photosynthesis of the grass (100 percent)is available to the hawk?

Accepted Answer

The transfer of energy between trophic levels in a food chain is not very efficient, with much energy lost to waste heat, respiration, and other metabolic processes. As a result, only about 10% of the energy in one trophic level is typically available to the next level. This is known as the 10% rule. Hence, the energy available to the snake from the mouse would be 0.1%, energy available to the mouse from the grasshopper would be 1%, and energy available to the grasshopper from the grass would be 10%. Therefore, the energy available to the hawk from the grass is only about 0.01%.

Question 13

Owls eat rats, mice, shrews, and small birds. Assume that, over a period of time, an owl consumes 5,000 J of animal material. The owl loses 2,300 J in feces and owl pellets and uses 2,500 J for cellular respiration. What is the production efficiency of this owl?

Accepted Answer

To find the production efficiency, we need to subtract the energy lost in feces and pellets and energy used in cellular respiration from the energy consumed. 
Energy consumed = 5,000 J 
Energy lost in feces and pellets = 2,300 J 
Energy used in cellular respiration = 2,500 J 
Energy available for growth and reproduction = Energy consumed - energy lost in feces and pellets and energy used in cellular respiration 
= 5,000 - 2,300 - 2,500 J 
= 1,200 J 
Production efficiency = (Energy available for growth and reproduction / Energy consumed) x 100% 
= (1,200 / 5,000) x 100% 
= 24% 
Therefore, the production efficiency of this owl is 7.4%, which is closest to option B.

Question 14

If you applied a fungicide to a cornfield, what would you expect to happen to the rate of decomposition and net ecosystem production (NEP)?

Accepted Answer

Fungicides target fungi, many of which are decomposers that break down organic matter. By reducing fungal populations, the decomposition rate would decrease. This could lead to more organic material being retained within the ecosystem, potentially increasing the net ecosystem production (NEP) as more carbon is stored in biomass rather than being released through decomposition.

Question 15

Which of the following ecosystems would likely have the largest net primary productivity per hectare and why?

Accepted Answer

Grasslands have a high net primary productivity due to their rapid growth, high turnover rate, and small standing crop biomass resulting from consumption by herbivores and rapid decomposition.

Question 16

Which trophic level is most vulnerable to extinction?

Accepted Answer

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Question 17

For most terrestrial ecosystems, pyramids composed of species abundances, biomass, and energy are similar in that they have a broad base and a narrow top. The primary reason for this pattern is that ________.

Accepted Answer

The broad base and narrow top of pyramids of species abundances, biomass, and energy is due to the fact that at each step of energy transfer within an ecosystem, there is a loss of energy, usually in the form of heat. This means that there is less and less energy available to support higher trophic levels, resulting in a narrower top of the pyramid. Therefore, choice B is the correct answer. The other choices are incorrect as they do not explain the broad base and narrow top pattern.

Question 18

Why does a vegetarian leave a smaller ecological footprint than an omnivore?

Accepted Answer

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Question 19

Suppose you are studying the nitrogen cycling between vegetation, sediments, and water in a pond ecosystem over the course of a month. While you are collecting data, a flock of 100 Canada geese lands and spends the night during a fall migration. What could you do to eliminate error in your study as a result of this event?

Accepted Answer

Option C is the best choice as it takes into account both the consumption and elimination of nitrogen by the Canada geese. By finding out the amount of nitrogen consumed and eliminated by a single Canada goose over a 12-hour period, and then multiplying this value by 100 and including it as a +/- value in the nitrogen budget, the effects of the geese can be accounted for in the study. Option A and B only consider one aspect of the Canada geese's impact on the ecosystem, while Option D is not a practical or ethical solution.

Question 20

Which one of the following correctly ranks these organisms in order from lowest to highest percent in production efficiency?

Accepted Answer

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Quiz 55: Ecosystems and Restoration Ecology