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Food Chain Quiz 26 (2 MCQs)

This set of multiple-choice questions evaluates understanding of energy transfer in ecosystems, including trophic levels, food chain efficiency, and bioaccumulation of toxic chemicals. It tests knowledge of how energy flows through a food chain and the concentration of toxic substances at different trophic levels.

Quiz Instructions

Select an option to see the correct answer instantly.

1. Consider the following food chain:Algae > Mayfly > Minnow > Trout In a polluted ecosystem, which organism is likely to have the HIGHEST level of toxic chemicals in its body?

Correct Answer: Correct answer is: (D) Trout.

Exam Relevance: AP Environmental Science, IB Environmental Systems and Societies, MCAT

Difficulty: Moderate

Concept notes: In a food chain, toxic chemicals tend to bioaccumulate, meaning they increase in concentration as they move up the trophic levels.

Common Mistakes: A common misunderstanding is that the organism at the bottom of the food chain would have the highest concentration of toxic chemicals, but this is incorrect because bioaccumulation increases the concentration at higher trophic levels.

Explanations: Toxic chemicals in the environment are absorbed by primary producers like algae. These chemicals are then passed up the food chain. Each organism at a higher trophic level consumes multiple organisms from the lower trophic level, leading to a higher concentration of toxic chemicals in their bodies. Therefore, the trout, being at the top of the food chain, would have the highest level of toxic chemicals.

Option Analysis:

Option A: Algae are primary producers and do not bioaccumulate toxic chemicals to the same extent as higher trophic levels.
Option B: Mayflies consume algae and thus have some toxic chemicals, but not as much as organisms at higher trophic levels.
Option C: Minnows consume mayflies and thus have a higher concentration of toxic chemicals than mayflies, but not as high as trout.
Option D: Trout consume minnows and thus have the highest concentration of toxic chemicals due to bioaccumulation.

2. Given below is a food chain of a terrestrial ecosystem.Grass $\rightarrow$ Grasshopper $\rightarrow$ Frog $\rightarrow$ SnakeIf the energy available to heterotrophs at the level of grass is 100 KJ, what will be the amount of energy available to frogs?

Correct Answer: Correct answer is: (B) 1000 J.

Exam Relevance: AP Environmental Science, IB Biology, SAT Subject Test in Biology

Difficulty: Moderate

Concept notes: In a food chain, energy transfer efficiency between trophic levels is typically around 10%. This means that only about 10% of the energy available at one trophic level is transferred to the next higher trophic level.

Common Mistakes: A common mistake is to assume that energy transfer efficiency is higher or lower than 10%, leading to incorrect calculations of energy available at each trophic level.

Explanations: Given that the energy available to heterotrophs at the level of grass is 100 KJ, we need to calculate the energy available to frogs, which are at the third trophic level (grasshopper being the second trophic level). 1. Energy available to grasshoppers (second trophic level) = 10% of 100 KJ = 10 KJ. 2. Energy available to frogs (third trophic level) = 10% of 10 KJ = 1 KJ = 1000 J. Thus, the amount of energy available to frogs is 1000 J.

Option Analysis:

Option A: 10,000 J is incorrect because it is too high, as only 10% of the energy is transferred at each trophic level.
Option B: 1000 J is correct as it follows the 10% energy transfer rule from one trophic level to the next.
Option C: 100 J is incorrect because it is too low, as it would imply a much lower energy transfer efficiency than the typical 10%.
Option D: 10 J is incorrect because it is too low, as it would imply a much lower energy transfer efficiency than the typical 10%.

Frequently Asked Questions

What is a food chain?

A food chain is a linear sequence of organisms through which nutrients and energy pass as one organism eats another.

How does energy transfer efficiency work in a food chain?

Energy transfer efficiency in a food chain is typically low, with only about 10% of energy from one trophic level being transferred to the next.

What are trophic levels?

Trophic levels are the feeding positions in a food chain, such as producers, primary consumers, and secondary consumers.

How does bioaccumulation affect organisms in a food chain?

Bioaccumulation occurs when toxic chemicals build up in organisms over time, often increasing in concentration at higher trophic levels.

Why is it important to understand food chains?

Understanding food chains helps in comprehending the interdependence of organisms and the flow of energy in ecosystems.

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