Question 1

If a person needs to consume 100 kcal of energy and he chooses to do that by eating soybeans, at least how many kcal of soybeans would have to grow to provide that 100 kcal for the human?

Accepted Answer

Soybeans have an average energy density of 1736 kcal/kg. Therefore, to provide 100 kcal of energy, at least 100/1736 = 0.0576 kg or 57.6 g of soybeans would have to be grown. To convert this to kcal, we need to multiply by the energy density, which gives 0.0576 x 1736 = 100.01 kcal. Therefore, at least 100 kcal of soybeans would need to be grown to provide the required energy. The only option that comes close to this is option B, which is 1,000 kcal.

Question 2

You are studying a grassland ecosystem with 400,000 kcal of energy stored in the primary producer level. Grasshoppers eat the grass, meadowlarks eat the grasshoppers, and a hawk eats the meadowlarks. How many kcals are now stored, and available, in the hawk?

Accepted Answer

As per the 10% rule of energy transfer in food chains, only 10% of the energy stored in a trophic level is available for the next level. So, from the 400,000 kcal stored in the primary producer level, only 40,000 kcal will be available at the grasshopper level (10% of 400,000). Similarly, only 4,000 kcal will be available at the meadowlark level (10% of 40,000), and finally, only 400 kcal will be available at the hawk level (10% of 4,000). Therefore, the answer is C) 400.

Question 3

Which of the following describes the ultimate disposition of most energy in an ecosystem?

Accepted Answer

The ultimate fate of most energy in an ecosystem is to be dissipated into the environment in the form of heat, which eventually radiates back into space. This process is known as the Second Law of Thermodynamics, which states that energy always flows from a more concentrated and useful form to a less concentrated and less useful form. Therefore, option D is the correct answer.

Question 4

If there are 50 kcal of energy in the tertiary consumer trophic level, how many kcal would you expect to find in the primary consumer level?

Accepted Answer

The answer of If there are 50 kcal of energy...

Question 5

Human activities

Accepted Answer

Human activities, such as agriculture, urbanization, and deforestation, can alter nutrient cycles both locally and globally. For example, excessive use of fertilizers in agriculture can lead to eutrophication of nearby water bodies, while deforestation can disrupt the water cycle and nutrient cycling in the affected area.

Question 6

Tuna are predatory fish that consume smaller, carnivorous fish that have fed on zooplankton. The zooplankton had fed on phytoplankton. When you eat tuna, you are consuming what level of the food chain?

Accepted Answer

The answer of Tuna are predatory fish that consume smaller,...

Question 7

Tuna are predatory fish that consume smaller, carnivorous fish that have fed on zooplankton. The zooplankton had fed on phytoplankton. You eat tuna, you are what level of the food chain?

Accepted Answer

The answer of Tuna are predatory fish that consume smaller,...

Question 8

On average, what percentage of the energy from one trophic level of an energy pyramid is transferred to the next trophic level?

Accepted Answer

On average, only 10 percent of the energy from one trophic level is transferred to the next trophic level. This is known as the 10% rule. The rest of the energy is lost as heat or used for the organism's own life processes.

Question 9

If there are 20,000 kcal available in the primary producer level of an ecosystem, how many kcal would be available in the secondary consumer level?

Accepted Answer

The answer of If there are 20,000 kcal available in...

Question 10

When humans consume rice they occupy which trophic level of a food chain?

Accepted Answer

Humans consume rice, which is a plant-based food source. Therefore, they occupy the trophic level of a primary consumer, as they are herbivores that feed on producers.

Question 11

In the diagram below, how do nutrient and energy flow differ?

Accepted Answer

Energy flow is one-way because it is constantly being lost as heat as it moves through the food chain, whereas nutrients are recycled as they move through the food chain. Nutrients are taken in by organisms, used for growth and metabolism, and then released back into the environment as waste or when organisms die, which can then be taken up by other organisms. This continual recycling of nutrients allows for a more efficient use of resources in the ecosystem.

Question 12

If there are 5,000,000 kcal of energy stored in grain that could be fed either to beef cattle or humans and you choose to feed the grain to the cattle to fatten them up for the humans, how many kcal would now be available as beef to feed the humans?

Accepted Answer

Only 10% of the energy from the grain is typically converted into beef energy, so 500,000 kcal would be available as beef energy to feed the humans.

Question 13

If there are 5,000,000 kcal of energy stored in grain that could be fed either to chickens or humans and there is a small village of starving people that need to be fed, what is the most efficient way to feed the majority of the villagers?

Accepted Answer

The answer of If there are 5,000,000 kcal of energy...

Question 14

When humans consume herbivores such as cattle, they occupy which trophic level of a food chain?

Accepted Answer

Herbivores such as cattle are primary consumers because they consume plants, which are the primary producers in the food chain. When humans consume herbivores, they occupy the secondary consumer trophic level.

Question 15

In the absence of ________, nutrients would not move from the abiotic to the biotic portion of the nutrient cycle within an ecosystem.

Accepted Answer

Primary producers, also known as autotrophs, convert abiotic nutrients into organic matter through photosynthesis or chemosynthesis. This organic matter then becomes the base of the food chain for herbivores, carnivores, and omnivores, allowing nutrients to cycle through the ecosystem. Without primary producers, there would be no source of organic matter for other organisms to consume, and the nutrient cycle would not be able to proceed.

Question 16

If a person needs to consume 100 kcal of energy and she chooses to do that by eating chicken, how many kcal of grain would the chicken need to consume to make 100 kcal available to the human?

Accepted Answer

The answer of If a person needs to consume 100...

Question 17

How might a decline in phytoplankton affect the climate of Earth?

Accepted Answer

A decline in phytoplankton could reduce the amount of carbon dioxide (a greenhouse gas) being removed from the atmosphere, which could contribute to global warming. Phytoplankton are a key component of the ocean's carbon cycle, and when they die, they sink to the ocean floor carrying carbon with them. If there is less phytoplankton, less carbon will be removed from the atmosphere and more will contribute to global warming.

Question 18

What is the primary difference between consumers and decomposers?

Accepted Answer

The primary difference between consumers and decomposers is that consumers obtain their nutrients by eating other live organisms while decomposers obtain their nutrients from dead consumers. Consumers are able to digest and absorb nutrients from other living organisms, while decomposers break down the remains of dead organisms to obtain their nutrients.

Question 19

Your spacecraft crash-lands on an airless, lifeless moon. All that survives, along with the crew and you, are some chickens, cornflakes, and vitamins. The air and water recyclers are functioning. To maximize the food supply until a rescue craft arrives, you and the crew should

Accepted Answer

The answer of Your spacecraft crash-lands on an airless, lifeless...

Question 20

Energy does not cycle through an ecosystem. This is because energy enters an ecosystem through photosynthesis as it changes to chemical energy. This is then used to fuel metablic activities

Accepted Answer

Energy enters an ecosystem through photosynthesis in producers, is passed on to consumers as they eat the producers or other consumers, and is eventually returned to the ecosystem through decomposition by decomposers. However, with each transfer of energy, some energy is lost as metabolic heat. Therefore, energy does not cycle but rather flows through the ecosystem.

Quiz 18: Ecosystems