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
Lesson Notes (7.11.2014)
|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 Footprints Science (click here)
BBC Bitesize video (click here)
My GCSE Science video (click here)