Biology

20.1 - Food Production

1 min

note 1 of 1

Crops versus livestock - Energy efficiency

Energy is lost at every step up a food chain.
When an organism is eaten, only about a tenth of the energy stored in it becomes body mass in the organism that eats it.
The rest is lost - mostly as heat from respiration and in waste.
This makes each transfer of energy between trophic levels very inefficient.

If a person eats meat from an animal fed on plants, there is an extra trophic level - the animal - between the person and the original plants, so most of the energy is lost in that extra step.
If the person eats the plants directly, that energy loss is avoided.
So it's more energy-efficient for people to eat crops than to eat livestock that have been fed on crops.
Farming crops to feed humans directly produces far more food from a given amount of plant material than farming the same crops to feed animals that are then eaten.

end of notes

Biology

1 min

note 1 of 1

Energy is lost at every step up a food chain.
When an organism is eaten, only about a tenth of the energy stored in it becomes body mass in the organism that eats it.
The rest is lost - mostly as heat from respiration and in waste.
This makes each transfer of energy between trophic levels very inefficient.

If a person eats meat from an animal fed on plants, there is an extra trophic level - the animal - between the person and the original plants, so most of the energy is lost in that extra step.
If the person eats the plants directly, that energy loss is avoided.
So it's more energy-efficient for people to eat crops than to eat livestock that have been fed on crops.
Farming crops to feed humans directly produces far more food from a given amount of plant material than farming the same crops to feed animals that are then eaten.

end of notes