Oxford AQA IGCSE · CORE Biology (9221)
5 multiple-choice questions marked as you go, and 4 written questions with worked solutions. All on Energy transferred in ecosystems.
A coastal ecosystem receives an average of \( 6,000,000 \text{ kJ} \) of incident light energy from the Sun per day. The energy flows through the following food chain:
Phytoplankton → Zooplankton → Small Fish → Large Predatory Fish
Using the standard syllabus percentages for energy transfer from sunlight to producers (\( 1\% \)) and between subsequent trophic levels (\( 10\% \)), calculate the amount of energy that would be available in the biomass of the Large Predatory Fish.
In a simple food chain: Grass → Grasshopper → Frog → Snake, the grass receives \( 2,000,000 \text{ kJ} \) of incident light energy from the sun. Based on the standard percentage of energy transfer for photosynthesis, calculate the energy available in the biomass of the Frogs, assuming a \( 10\% \) efficiency at each subsequent trophic level.
In a food chain, only about \(10\%\) of the biomass from one trophic level is transferred to the next. Which of the following is a reason for this loss of biomass?
A group of students measured the biomass of different trophic levels in a stable woodland ecosystem. They found that only about \(10\%\) of the biomass is transferred from the primary consumers to the secondary consumers.
What is the most likely reason for this loss of biomass?
In an ecosystem, energy is transferred between trophic levels. A community receives \( 8,500,000 \text{ kJ} \) of incident light energy from the Sun per day.
Calculate the energy stored in the primary consumers, assuming producers transfer \( 1\% \) of incident energy and there is a \( 10\% \) efficiency of transfer to the next level.
A food chain consists of a producer, a primary consumer, and a secondary consumer. Explain two distinct biological reasons why only approximately \(10\%\) of the biomass is transferred between these trophic levels.
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Energy enters most ecosystems via photosynthesis. If a field of crops receives \( 8,000,000 \text{ kJ} \) of incident light energy, calculate the energy stored in the producers and then the energy transferred to primary consumers, using standard syllabus percentages.
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A farmer investigates the movement of energy through a small ecosystem on her land. She estimates that the total incident energy from sunlight hitting a field of clover plants is \( 2,500,000 \text{ kJ} \).
a) Calculate the amount of energy stored in the clover plants through photosynthesis, assuming they transfer the standard percentage of incident light energy as stated in the OxfordAQA syllabus.
b) If a population of rabbits eats the clover, and a fox then eats the rabbits, calculate the approximate energy available to the fox.
c) Explain two reasons why such a small percentage of the energy from the rabbits is actually transferred to the biomass of the fox.
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A small island ecosystem receives \( 4,500,000 \text{ kJ} \) of incident solar radiation every day. This energy supports a food chain consisting of seaside grass, grasshoppers, and insect-eating birds.
a) Calculate the energy stored in the biomass of the seaside grass, assuming the standard percentage of incident light energy transfer for photosynthesis as defined in the syllabus. Give your answer in \( \text{kJ} \).
b) If all of this seaside grass is consumed by grasshoppers, calculate the amount of energy that would be transferred to the biomass of the grasshopper population.
c) State two specific ways in which energy is lost from the grasshopper population before it can be transferred to the birds.
d) Based on the efficiency of energy transfer, suggest one way the efficiency of food production could be improved for human consumption according to the syllabus principles.
Write your answer out first, then check it against the worked solution.
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