1
1 mark
1 markA food chain is shown below.
tree ➔ small insects ➔ small birds ➔ birds of prey
One of the pyramids of number below represents this food chain.
Which one would be correct?
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Energy Flow (Cambridge O Level Biology)
Topic Questions
21 mark
1 markWhich of the following diagrams show a pyramid of biomass for a forest?
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31 mark
The diagram shows a pyramid of biomass for a food chain.
Which level represents the producers?
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11 mark
1 markWhich statement gives the best explanation for why most food chains have no more than five trophic levels?
Because 20% of the energy is transferred at each level and after 5 levels, all the energy is used up (5 × 20% = 100%).
The numbers of organisms are insufficient because the top predator has to have a count of 1 in a pyramid of numbers.
The biomass transferred from a consumer to the next-level consumer is too little.
There is a large amount of energy loss at each level so insufficient energy can be passed up to the sixth trophic level.
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21 mark
1 markLook at the information about a food chain.
| Organism | Number | Biomass / kg |
| Oak tree | 1 | 400,000 |
| Aphids | 9,000 | 900 |
| Predatory midges | 120 | 45 |
What is the percentage biomass of the aphids transferred to the midges?
0.05 %
1.3 %
5%
0.225 %
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31 mark
The graph shows changes in the populations of plant and animal plankton (microscopic organisms) in a lake. 
Consider the following statement in relation to the data provided by the graph.
‘Population changes in animal plankton occur after similar changes in plant plankton because the animals feed on the plants.’
Which description fits this statement?
It is a possible interpretation of the data.
The data do not support the statement.
The data are too random to be interpreted.
It is the only way to interpret the data
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11 mark
1 markThe image below shows a pyramid of biomass for a food chain in a rainforest ecosystem.
What would be an appropriate pyramid of numbers for this food chain?
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21 mark
1 markThe image shows a food web.
Which organism, from the food web, feeds on the greatest variety of organisms?
Whelks
Crabs
Limpets
Mussels
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31 mark
1 markWhich letter shows the path of the energy from the sun?
chemical energy in sugars → stored in plants → trapped in chlorophyll
trapped in chlorophyll → chemical energy in sugars → stored in plants
stored in plants → chemical energy in sugars → trapped in chlorophyll
stored in plants → trapped in chlorophyll → chemical energy in sugars
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41 mark
These processes occur in living organisms in a food chain.
| 1 | excretion |
| 2 | photosynthesis |
| 3 | respiration |
Which processes would result in a loss of energy from a food chain?
1 and 2
1 and 3
2 only
3 only
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51 mark
Which statements are correct?
| 1 | Energy cannot be recycled in food webs. |
| 2 | Producers make their own organic nutrients. |
| 3 | The Sun is the principal source of energy input to biological systems. |
1, 2 and 3
1 and 2 only
1 and 3 only
2 and 3 only
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61 mark
When untreated sewage flows into a river, why does the oxygen concentration decrease?
Less oxygen is absorbed from the air
There is a decrease in the number of plants
There is an increase in the number of bacteria
There is an increase in the number of fish
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