B1.5 Energy and biomass in food chains



Radiation from the Sun is the source of energy for most communities of living organisms.

Green plants and algae absorb a small amount of the light that reaches them.
The transfer from light energy to chemical energy occurs during photosynthesis.
This energy is stored in the substances that make up the cells of the plants.

The mass of living material (biomass) at each stage in a food chain is less than it was at the previous stage.

The biomass at each stage can be drawn to scale and shown as a pyramid of biomass.

Biomass means the dry mass of living material at a stage in a food chain (that is body mass without water).

Biomass at a particular stage = dry mass of a single organism  × the number of that organism (population)


Biomass decreases as you go up the pyramid and move to the next stage in the food chain because:

■ some materials and energy are always lost in the organisms’ waste materials
respiration supplies all the energy needs for living processes, including movement. Much of this energy is eventually transferred to the surroundings
■ some of the available energy goes into growth and the reproduction of offspring.




Some practice questions

This slideshow requires JavaScript.

Lesson Notes (7.11.2014)

Key words

Word Meaning
producers green plants and algae; they make food by photosynthesis
primary consumers usually eat plant material – they are herbivores; for example rabbits, caterpillars, cows and sheep
secondary consumers usually eat animal material – they are carnivores; for example cats, dogs and lions
predators kill for food; they are either secondary or tertiary consumers
prey the animals that predators feed on
scavengers feed on dead animals; for example, crows, vultures and hyenas are scavengers
detritivores feed on dead and decaying organisms, and on the undigested parts of plant and animal matter in faeces. Examples include:
earthworms that help break down dead leaves; maggots that feed on animal tissue; woodlice that break down wood


Simulations from Boardworks (Quiz) (Missing Words Quiz)


Simulations from Footprints Science (click here)











BBC Bitesize video (click here)



My GCSE Science video (click here)