GCSE Biology Unit 2 (10)

Energy Transfer and Decay

• Energy from the Sun is the source of nearly all life on Earth.
• Plants use a small percentage of the light energy from the Sun to make food during photosynthesis.
• This energy's stored in the substances which make up the cells of plants, and then works its way through the food web as animals eat the plants and each other.
• Respiration supplies the power for all life processes, including movement.
• Most energy is eventually lost to the surroundings as heat.
• This is especially true for mammals and birds, whose bodies must be kept at a constant temperature which is normally higher than their surroundings.
• Some of the material which makes up plants and animals is inedible, so it doesn't pass on to the next stage of the food chain.
• Material and energy are also lost from the food chain in excretion.
• This explains why you hardly ever get food chains with more than about 5 trophic levels.
• So…