Biology - Energy and Biomass

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.

 Photosynthesis = water + carbon dioxide --> glucose + oxygen

A food chain shows what eats what in a particular habitat. Pyramids of biomass reveal the mass of living material at each stage in a food chain. The amount of biomass (and energy) decreases from one stage to another. This is because:

• some materials and energy are lost in the organism's waste material
• respiration supplies all the energy for living processes, including movement and heating (in warm-blooded animals). Much of this energy is eventually transferred to the surroundings

An example of a food chain:

Oak tree  ---->   Caterpillar      ---->       Blue ***     ---->     Sparrowhawk

Producer      Primary Consumer  Secondary Consumer  Tertiary Consumer

Biomass is the dry mass of a living material (at a stage in the food chain). Biomass decreases from one trophic level to another, just like the amount of energy. The bars become narrower as you reach the top of the diagram.

The efficiency of food production can be improved by:

• reducing number of stages in food chain
• restricting energy loss from animals through limiting movement and controlling temperature of their surroundings

Managing Food Production

Fish stocks in the ocean are declining - it is important to maintain the at a point where breeding can continue, otherwise certain species may become extinct - two important factors in managing this are net sizes and fishing quotas.

Compromises of managing food production/distribution

• Differences in efficiency between animal and plants in terms of production
• Ethical issues associated with the 'factory farming' of animals
• Implication of 'food miles'