Compare direct crop eating with livestock
Eating crop plants directly avoids an extra trophic transfer through livestock, so more of the crop’s energy can be available to people.
Mapped to the named 0654 section using teaching from the corresponding single-science course. A 0654-specific review of every Core and Supplement objective is still in progress. Written practice is self-checked; it does not demonstrate supervised laboratory competence or award an official Cambridge grade.
Before you begin
- Read energy-transfer arrows and distinguish energy from matter in the 19.1 Energy flow pathway.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
Why is eating crop plants directly more energy efficient in the syllabus comparison?
What you will learn
- Explain the energy advantage of eating crop plants directly
- Account for energy used or not transferred through livestock
Avoid an additional transfer
Crop plants store chemical energy in organic material. If people eat the crop directly, that energy enters the human food pathway without first passing through livestock. If livestock eat the crop, some energy is used in animal respiration, movement and other life processes; some material is not eaten or assimilated. Less energy from the crop is therefore available in animal material for people.
This is a comparison of energy efficiency in the stated food route: crop → human has fewer transfer steps than crop → livestock → human. It does not by itself compare nutrition, cultural choices, land use or the full environmental impact of diets.
Explain the direction, not a fixed percentage
Use an energy-flow argument: an additional trophic level means an additional transfer at which energy is used or not passed on. The exact amount depends on the crop, livestock and conditions; do not invent a universal percentage.
In a question, identify the crop energy source, the extra livestock step, and at least one route by which energy is not available to humans. Keep the conclusion within the comparison given.
Sources for this lesson
Pause and explain
Which explanation best supports the comparison?
Worked example
Explain why eating grain directly is more energy efficient for humans than feeding the grain to livestock and eating the livestock.
Show the worked solution
- Direct grain eating avoids an extra trophic transfer.
- Livestock use some energy in respiration and movement.
- Not all grain or animal material becomes food for humans.
Answer Eating grain directly avoids the livestock trophic level. Livestock use energy in respiration and movement, and not all crop energy is converted into edible animal material, so a smaller fraction is available to humans through the livestock route.
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Test this topic →From guided practice to a new situation
Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
A person can eat beans directly or feed them to livestock and later eat the livestock. Explain the energy advantage of the direct route.
Give me a hint
Compare the number of trophic transfers.
Compare my reasoning
- Beans → human has one feeding transfer.
- Beans → livestock → human has an extra transfer.
- Livestock use energy in life processes.
Eating beans directly avoids an extra trophic level. Livestock use energy in respiration and movement, and not all bean energy becomes edible animal material, so more crop energy is available through the direct route.
Look for these in your work
- Routes compared
- Loss pathway explained
A learner concludes “every crop-based meal is nutritionally better than every animal product.” Why does the energy argument not support this conclusion?
Give me a hint
Limit the conclusion to the syllabus comparison.
Compare my reasoning
- Energy efficiency concerns transfer through trophic levels.
- Nutrition depends on other information not supplied by this comparison.
The energy argument says direct crop eating avoids an extra transfer and can make more crop energy available to people; it does not compare nutritional quality or establish a universal diet recommendation.
Look for these in your work
- Claim bounded
- What energy comparison says included
A farmer reports no energy values but asks which route has fewer transfer losses: crop → people or crop → livestock → people. Answer without inventing a percentage.
Give me a hint
Count the transfers and state the general reason.
Compare my reasoning
- Direct crop eating avoids the livestock step.
- Livestock use some energy and do not transfer all crop material to people.
Crop → people has fewer trophic transfers. It avoids losses through an additional livestock level, though no exact percentage can be calculated from the information given.
Look for these in your work
- Fewer transfers identified
- No unsupported number
Common mistakes
- Claiming all crop energy transfers to humans directly
- Turning the energy comparison into a complete diet recommendation
- Inventing a universal percentage advantage
What can you explain now?
Why is eating crop plants directly more energy efficient in the syllabus comparison?
Compare with the explanation
It avoids an extra trophic transfer through livestock
Livestock use energy and do not pass all crop energy to people.
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Make it stick
Explain why people eating crop plants is more energy efficient than eating livestock fed on those crops.
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.