Free Ecology Ecosystem Energy Flow Questions and Answers — Questions and Answers
Question 1: In a terrestrial ecosystem, if the primary producers generate 10,000 kcal/m²/year of energy, approximately how much energy would be available to the tertiary consumers?
- 1,000 kcal/m²/year
- 100 kcal/m²/year
- 10 kcal/m²/year (Correct answer)
- 1 kcal/m²/year
Correct answer: 10 kcal/m²/year
The 10% rule of energy transfer states that only about 10% of the energy from one trophic level is transferred to the next. Primary producers (10,000 kcal) are eaten by primary consumers (10% of 10,000 = 1,000 kcal). Primary consumers are eaten by secondary consumers (10% of 1,000 = 100 kcal). Secondary consumers are eaten by tertiary consumers (10% of 100 = 10 kcal).
Question 2: Which of the following best defines Net Primary Production (NPP)?
- The total rate of photosynthesis, including the energy used by producers for respiration.
- The energy that is transferred from primary producers to primary consumers.
- The rate at which decomposers break down organic matter.
- The rate of energy stored as biomass by producers and made available to consumers. (Correct answer)
Correct answer: The rate of energy stored as biomass by producers and made available to consumers.
Net Primary Production (NPP) is the Gross Primary Production (GPP) minus the energy lost by producers for their own respiration (R). Therefore, NPP represents the energy stored as new biomass that is available to the next trophic level.
Question 3: The pyramid of energy in an ecosystem is always upright and can never be inverted. What is the fundamental reason for this?
- The biomass of producers is always greater than the biomass of consumers.
- Energy is lost as heat at each successive trophic level according to the laws of thermodynamics. (Correct answer)
- Decomposers are not included in the pyramid, which skews the shape.
- The number of individual organisms always decreases at higher trophic levels.
Correct answer: Energy is lost as heat at each successive trophic level according to the laws of thermodynamics.
The pyramid of energy is always upright because energy transfer between trophic levels is inefficient. A significant amount of energy is lost as heat during metabolic processes at each level, as described by the Second Law of Thermodynamics. This means that the total energy available at a higher trophic level is always less than the total energy at the level below it.
Question 4: In a deep-sea hydrothermal vent ecosystem, which type of organism forms the base of the food web by harnessing chemical energy?
- Photosynthetic algae
- Detritivores
- Chemoautotrophic bacteria (Correct answer)
- Bioluminescent fungi
Correct answer: Chemoautotrophic bacteria
In deep-sea hydrothermal vents, there is no sunlight for photosynthesis. Instead, chemoautotrophic bacteria form the base of the food web. They derive energy from the oxidation of inorganic compounds, such as hydrogen sulfide, released from the vents to produce organic matter.
Question 5: A lake is contaminated with a persistent, fat-soluble pesticide. Which of the following organisms would likely have the HIGHEST concentration of this pesticide in its tissues?
- Phytoplankton
- A large predatory fish that eats other fish (Correct answer)
- A small fish that feeds on zooplankton
- Zooplankton that feeds on phytoplankton
Correct answer: A large predatory fish that eats other fish
This scenario describes biomagnification, where the concentration of a toxin increases at successively higher levels in a food chain. The pesticide accumulates in the fatty tissues of organisms at each trophic level. The large predatory fish, being at the top of this food chain, consumes many smaller fish, each containing the pesticide, leading to the highest concentration in its own body.
Question 6: What is the crucial role of decomposers, such as bacteria and fungi, in the flow of energy through an ecosystem?
- They convert solar energy into chemical energy for producers.
- They are the primary food source for all tertiary consumers.
- They release stored energy and nutrients from dead organic matter, making them available to producers. (Correct answer)
- They create energy through the process of chemosynthesis.
Correct answer: They release stored energy and nutrients from dead organic matter, making them available to producers.
Decomposers break down dead organisms and waste products from all trophic levels. In doing so, they release the energy stored within this organic matter and, more importantly, return essential nutrients (like nitrogen and phosphorus) to the soil and water, where they can be taken up by primary producers, thus completing the nutrient cycle.
Free Ecology Ecosystem Energy Flow Questions and Answers
In a terrestrial ecosystem, if the primary producers generate 10,000 kcal/m²/year of energy, approximately how much energy would be available to the tertiary consumers?