MISA - Maryland Integrated Science Assessment Ecosystems Matter and Energy Questions and Answers — Questions and Answers
Question 1: In a forest ecosystem, a deer eats plants, a wolf eats the deer, and fungi break down the wolf's remains after it dies. Which of the following correctly describes the flow of energy in this ecosystem?
- Energy flows from the plants to the deer, then to the wolf, and is finally recycled by the fungi back to the plants.
- Energy flows from the sun to the plants, then to the deer, and then to the wolf. The fungi do not use energy.
- Energy flows from the sun to the plants, then to the deer, and then to the wolf. Energy is transferred to the fungi from the wolf's remains. (Correct answer)
- Energy flows from the plants to the sun, is absorbed by the deer and wolf, and is destroyed by the fungi.
Correct answer: Energy flows from the sun to the plants, then to the deer, and then to the wolf. Energy is transferred to the fungi from the wolf's remains.
Energy in most ecosystems originates from the sun and is captured by producers (plants) through photosynthesis. This energy is then transferred to primary consumers (deer) and then to secondary consumers (wolf). When the wolf dies, decomposers (fungi) obtain energy by breaking down its organic matter. Unlike matter, energy is not recycled; it flows through the ecosystem and is lost as heat at each transfer.
Question 2: A biomass pyramid models the amount of living organic matter at each trophic level. In a stable grassland ecosystem, which trophic level would be expected to have the greatest amount of biomass?
- Secondary consumers (e.g., snakes)
- Producers (e.g., grasses) (Correct answer)
- Tertiary consumers (e.g., hawks)
- Primary consumers (e.g., grasshoppers)
Correct answer: Producers (e.g., grasses)
Producers form the base of the biomass pyramid and have the largest amount of living organic matter. This is because only a fraction of the energy and biomass from one trophic level is transferred to the next level above it. Therefore, the total mass of producers must be greater than the primary consumers they support, and so on up the pyramid.
Question 3: A student is designing a model to illustrate the cycling of carbon in an ecosystem. To accurately represent the process, which of the following components is essential to include as a mechanism that returns carbon dioxide to the atmosphere?
- Photosynthesis
- Transpiration
- Cellular Respiration (Correct answer)
- Nitrogen Fixation
Correct answer: Cellular Respiration
Cellular respiration is a process by which organisms (including plants, animals, and decomposers) break down organic compounds (like glucose) to release energy, with carbon dioxide being a primary waste product released back into the atmosphere. Photosynthesis removes CO2 from the atmosphere, transpiration releases water vapor, and nitrogen fixation converts nitrogen gas.
Question 4: If the primary producers in a marine food web store 25,000 kcal of energy, approximately how much energy would be available to the tertiary consumers in that same food web?
- 2,500 kcal
- 25 kcal (Correct answer)
- 250 kcal
- 2.5 kcal
Correct answer: 25 kcal
Only about 10% of the energy from one trophic level is transferred to the next. Therefore, primary consumers would receive about 2,500 kcal (10% of 25,000). Secondary consumers would receive about 250 kcal (10% of 2,500). Tertiary consumers would receive approximately 25 kcal (10% of 250).
Question 5: Which of the following statements best describes the primary difference between how matter and energy move through an ecosystem?
- Matter flows in one direction, while energy is recycled.
- Energy is created by producers, while matter is created by consumers.
- Matter and energy are both fully recycled by decomposers.
- Matter is cycled within the ecosystem, while energy flows through it. (Correct answer)
Correct answer: Matter is cycled within the ecosystem, while energy flows through it.
The key principle of ecosystem dynamics is that matter (like carbon, nitrogen, and water) is continuously cycled between living and nonliving components. In contrast, energy flows in one direction: from the sun, through the trophic levels, and is eventually lost as heat. It is not recycled.
Question 6: In an aquatic ecosystem, a sudden increase in agricultural runoff leads to eutrophication and a subsequent 'dead zone' where dissolved oxygen levels are extremely low. This condition is known as hypoxia. Which process is most directly inhibited in organisms living in this dead zone?
- Anaerobic respiration
- Photosynthesis
- Chemosynthesis
- Aerobic cellular respiration (Correct answer)
Correct answer: Aerobic cellular respiration
Aerobic cellular respiration is the process that uses oxygen to break down food molecules and release energy. In a hypoxic (low oxygen) environment, organisms that rely on this process cannot survive. Anaerobic respiration does not require oxygen. While the causes of the dead zone relate to photosynthesis (algal blooms), the direct process inhibited in animals by the lack of oxygen is aerobic respiration.
MISA - Maryland Integrated Science Assessment Ecosystems Matter and Energy Questions and Answers
In a forest ecosystem, a deer eats plants, a wolf eats the deer, and fungi break down the wolf's remains after it dies.
Which of the following correctly describes the flow of energy in this ecosystem?