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Pre AP Biology -ECO 2.3 Food Webs and Transfer of Energy in Ecosystems- MCQ Exam Style Questions -New Syllabus

Pre AP Biology -ECO 2.3 Food Webs and Transfer of Energy in Ecosystems- MCQ Exam Style Questions – New Syllabus 2025-2026

Pre AP Biology -ECO 2.3 Food Webs and Transfer of Energy in Ecosystems- MCQ Exam Style Questions – Pre AP Biology – per latest Pre AP Biology Syllabus.

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Question

Suppose you want to create an experimental grazing food web. Which of the following would you need to include so that it closely resembles a real grazing food web?
a. carnivores and decomposers
b. producers, herbivores, and detritivores
c. producers, herbivores, and carnivores
d. detritivores and decomposers
▶️ Answer/Explanation
Detailed solution

The correct answer is c.

A grazing food web is defined by its start with living photosynthetic producers.

Primary consumers (herbivores) must be present to graze upon these living plants.

Secondary consumers (carnivores) are needed to represent the higher trophic levels.

Options including detritivores or decomposers refer to the detrital food web.

In a grazing web, energy flows from producers $\rightarrow$ herbivores $\rightarrow$ carnivores.

Including all three groups ensures the experimental model mimics natural energy transfer.

Question

Use the trophic pyramid diagram to answer the questions below.
Q. The energy for use by organisms in Level A originally comes from
A. producers.
B. the Sun.
C. Level B.
D. Level D.
Q. If \(200,000\) joules of energy are found in Level C, the amount of energy transferred to Level D is approximately __________________ joules, while __________________ joules is lost as heat waste energy.
A. \(5,000\) ; \(195,000\)
B. \(20,000\) ; \(180,000\)
C. \(100,000\) ; \(100,000\)
D. \(190,000\) ; \(10,000\)
▶️ Answer/Explanation
Detailed solution

A: B. the Sun.
Level A is at the bottom of the pyramid, representing the producers.
Producers are autotrophs that synthesize their own food.
They utilize light energy to power photosynthesis.
Thus, the original source of energy is the Sun.

A: B. \(20,000\) ; \(180,000\)
According to the \(10\%\) rule, only \(10\%\) of energy transfers to the next level.
Energy transferred to Level D \(= 200,000 \times 0.10 = 20,000 \text{ J}\).
The remaining \(90\%\) is lost as heat or waste.
Energy lost \(= 200,000 – 20,000 = 180,000 \text{ J}\).

Question

A biologist analyzed a sample of pond water and recorded the different organisms in the sample. This table shows the number of each organism in the pond sample.
Why does the sample contain more phytoplankton than trout?
A. A trout requires less energy than a phytoplankton organism.
B. Phytoplankton receive energy from the other organisms.
C. Insect larvae obtain energy directly from the sun and transfer energy to the other organisms.
D. Phytoplankton obtain energy directly from the sun and transfer energy to the other organisms.
▶️ Answer/Explanation
Correct Answer: D
Detailed solution

Phytoplankton are producers that convert solar energy into chemical energy via photosynthesis.
In an ecological pyramid, producers must have the largest biomass and population to support higher levels.
As energy moves up the food chain (from larvae to frogs to trout), approximately $90\%$ of energy is lost as heat.
Because only $10\%$ of energy is transferred to each succeeding level, fewer organisms can be supported at the top.
Therefore, a massive base of phytoplankton is required to sustain a very small number of apex predators like trout.

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