Skip to content
Dabour HubLEARN · PRACTICE · EXPLORESign inStudent

3.4.1Unit 3 — Life on Earth

Energy Transfers

5 min read 4 parts Lesson 21 of 31

0%read

Section 1 of 4Energy Flow in Food Chains

3.4.1 Energy Transfers
Arrows
  • Arrows in a food chain show the direction in which energy stored in biomass is transferred.
Source
  • The energy in a food chain originally comes from the sun and is captured by producers in photosynthesis.
Transfer
  • When an animal eats its food, energy stored in the food organism's tissues passes to the consumer.
Most energy is lost
  • Only a small part of the energy transferred is turned into new biomass available to the next level.

Section 2 of 4Where Energy Is Lost

Where Energy Is Lost
Heat
  • Respiration releases energy as heat, which passes to the surroundings and cannot be stored by the consumer.
Movement
  • Energy used for movement ends up as heat and is no longer stored in the animal's biomass.
Undigested material
  • Parts of the food that are not digested leave the body in faeces, taking their energy with them.
Growth
  • Only the small amount of energy left over goes into growth and new biomass.

Section 3 of 4Following the Energy Along a Chain

Following one example shows why energy available falls at every step.

1
Grass captures light energy and stores it as chemical energy in its biomass.
2
A rabbit eats the grass but loses much of that energy as heat, in movement and in faeces.
3
A small part of the energy becomes new rabbit biomass, so less is available for the fox.
4
The fox eats the rabbit and again loses most of the energy it receives.
5
Because less energy is available at each stage, food chains are short and top predators are few.

Section 4 of 4Exam Checklist & Tips

3.4.1 – Key Points for the Exam

  • Biomass The mass of living material, which stores energy.
  • Energy transfer The movement of energy from one organism to the next along a food chain.
  • Producer An organism, such as a plant, that makes its own food by photosynthesis.
  • Consumer An organism that obtains energy by feeding on other organisms.
  • Trophic level A feeding position in a food chain.

Common Mistakes

  • Writing that energy is used up or disappears; it is lost to the surroundings, mostly as heat.
  • Saying all energy in food is passed on; most of it is lost at each step.
  • Forgetting undigested material in faeces as one way energy is lost.
  • Mixing up the arrow direction; arrows point from the food to the feeder.
\n