Question 1

Use the figure to answer the question:  Which arrow, if representing magnitude, should show the largest biomass exiting primary producers?

Accepted Answer

The answer of Use the figure to answer the question:...

Question 2

The flow of energy in an example arctic ecosystem goes through a simple food chain as depicted below:
Phytoplankton → zooplankton → fish → seals → polar bears
Which of the following is the most accurate conclusion when considering the energetics in this food chain?

Accepted Answer

In a typical food chain, energy is lost at each trophic level due to factors like metabolic processes and heat loss. Therefore, organisms lower in the food chain (like fish) generally have a greater biomass and can potentially provide more food for humans than organisms higher in the food chain (like seals).

Question 3

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, assuming a 10% trophic efficiency?

Accepted Answer

Trophic efficiency is 10%, so only 10% of the energy is transferred to each trophic level. Therefore, the hawk, which is at the top of the food chain, will have only 0.01% of the original energy fixed by photosynthesis.

Question 4

Which of the following is a reason that inefficient transfer of energy among trophic levels results in the typically high endangerment status of many top-level predators?

Accepted Answer

Top-level predators often have small populations that are sparsely distributed, which makes them more vulnerable to extinction. This vulnerability is exacerbated by the inefficient transfer of energy up the food chain, as less energy is available at higher trophic levels, supporting fewer individuals.

Question 5

Use the following figure to answer the question.  Diagram of a food web (arrows represent energy flow and letters represent species)
If the figure represents a terrestrial food web, the combined biomass of C + D would probably be ________.

Accepted Answer

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

Question 6

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

Accepted Answer

NEP accounts for the total carbon balance of an ecosystem, including both production and respiration, indicating whether the ecosystem is a carbon source or sink.

Question 7

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 8

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

Accepted Answer

Energy transfer between trophic levels is typically inefficient, with only about 10% of the energy from one level being passed to the next. This inefficiency limits the number of sustainable trophic levels in an ecosystem.

Question 9

Which of the following is a reason that a diet consisting primarily of fruits and vegetables results in a smaller ecological footprint than a diet high in meat content?

Accepted Answer

The answer of Which of the following is a reason...

Question 10

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

Accepted Answer

Satellites detect variable levels of productivity due to differences in ocean depth, nutrient availability, presence of coral reefs, and ocean currents, which affect net primary productivity (NPP) across different latitudes.

Question 11

Acid precipitation lowered the pH of soil in a terrestrial ecosystem that supported a diverse community of plants and animals. The decrease in pH eliminated all nitrogen-fixing bacteria populations in the area. Which prediction most accurately reflects the impact this will have on the community?

Accepted Answer

Nitrogen-fixing bacteria convert atmospheric nitrogen into forms that plants can absorb and use. Without these bacteria, plants cannot get enough nitrogen, leading to a deficiency that affects primary producers and, subsequently, the entire ecosystem's carrying capacity.

Question 12

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. Which of the following best estimates the production efficiency of this owl?

Accepted Answer

Production efficiency is calculated as (Net Secondary Production / Assimilation of Primary Production) * 100. Here, Net Secondary Production = Energy consumed - Energy lost in feces and pellets - Energy used for cellular respiration = 5,000 J - 2,300 J - 2,500 J = 200 J. Assimilation of Primary Production = Energy consumed - Energy lost in feces and pellets = 5,000 J - 2,300 J = 2,700 J. Thus, Production Efficiency = (200 / 2,700) * 100 ≈ 7.4%.

Question 13

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

Accepted Answer

Mammals have the lowest production efficiency due to high energy use for maintaining body temperature, followed by fish, and insects have the highest production efficiency.

Question 14

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

Accepted Answer

Grasslands typically have a high net primary productivity per hectare due to their rapid growth rates, efficient nutrient cycling, and the fact that much of the biomass produced is quickly consumed by herbivores or decomposed, allowing for continuous growth and nutrient reuse. This contrasts with ecosystems like the open ocean or deep ocean, where nutrient availability and light penetration can limit productivity, and the tundra, where the growing season is very short.

Question 15

Use the following figure to answer the question.  Which of the following claims is most consistent with the figure regarding productivity in this ecosystem?

Accepted Answer

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

Question 16

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

Accepted Answer

NEP is typically estimated by measuring the gas exchange (such as CO2 uptake) from vegetation, which gives an idea of the ecosystem's gross primary production, and then subtracting the respiration rates of all organisms in the ecosystem, including plants, animals, and microbes. This approach provides a net measure of the ecosystem's carbon sequestration ability or overall productivity.

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

At each trophic level, energy is lost primarily through metabolic processes as heat. This loss of energy at each step results in fewer organisms and less biomass being supported at higher trophic levels, leading to the characteristic broad base and narrow top of ecological pyramids.

Question 18

A porcupine eats 3,000 J of plant material. Of this, 2,100 J is indigestible and is eliminated as feces, 800 J are used in cellular respiration, and 100 J are used for growth and reproduction. What is the approximate production efficiency of this animal?

Accepted Answer

Production efficiency is calculated as the energy used for growth and reproduction divided by the total energy assimilated (the energy taken in minus the energy lost as feces), then multiplied by 100 to get a percentage. Here, it's (100 J / (3000 J - 2100 J)) * 100 = 3.33%, which rounds to approximately 3%, but since that option is not mathematically correct based on the given values, the closest correct option given is 11%. This seems to be a mistake in the calculation explanation provided; the correct calculation based on the provided options should lead to an understanding that the options might not accurately reflect the correct mathematical outcome. The correct approach would indeed suggest a different percentage, but given the options and typical calculations, there seems to be a misunderstanding in the explanation. The correct calculation should be (100 J / 900 J) * 100 = 11.11%, aligning with option C.

Question 19

Which of the following best explains the observation that matter may be gained by, or lost from, ecosystems?

Accepted Answer

Matter can be transferred between ecosystems through various processes such as water flow, wind, and the movement of animals, leading to a gain or loss of matter in a particular ecosystem.

Question 20

Use the following figure to answer the question.  Based on the figure, which of the following is the most complete explanation for the results?

Accepted Answer

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

Quiz 55: Energy Flow and Chemical Cycling in Ecosystems

Use the figure to answer the question: Which arrow, if representing magnitude, should show the largest biomass exiting primary producers?

The flow of energy in an example arctic ecosystem goes through a simple food chain as depicted below: Phytoplankton → zooplankton → fish → seals → polar bears Which of the following is the most accurate conclusion when considering the energetics in this food chain?

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, assuming a 10% trophic efficiency?

Which of the following is a reason that inefficient transfer of energy among trophic levels results in the typically high endangerment status of many top-level predators?

Use the following figure to answer the question. Diagram of a food web (arrows represent energy flow and letters represent species) If the figure represents a terrestrial food web, the combined biomass of C + D would probably be ________.

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

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?

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

Which of the following is a reason that a diet consisting primarily of fruits and vegetables results in a smaller ecological footprint than a diet high in meat content?

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

Acid precipitation lowered the pH of soil in a terrestrial ecosystem that supported a diverse community of plants and animals. The decrease in pH eliminated all nitrogen-fixing bacteria populations in the area. Which prediction most accurately reflects the impact this will have on the community?

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. Which of the following best estimates the production efficiency of this owl?

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

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

Use the following figure to answer the question. Which of the following claims is most consistent with the figure regarding productivity in this ecosystem?

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

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 ________.

A porcupine eats 3,000 J of plant material. Of this, 2,100 J is indigestible and is eliminated as feces, 800 J are used in cellular respiration, and 100 J are used for growth and reproduction. What is the approximate production efficiency of this animal?

Which of the following best explains the observation that matter may be gained by, or lost from, ecosystems?

Use the following figure to answer the question. Based on the figure, which of the following is the most complete explanation for the results?