Energy for life
All living things are active. Not just animals, but plants too.
All living things move. Plants can fold up their petals, shed their leaves, and move towards water or light. OK, so they’re usually slower than animals. But they often grow much faster than us – and growth is also an activity. In fact, it’s the most important activity of all.
Activity comes from energy, and energy comes from the sun. Plants capture that energy through photosynthesis, and bring it into the food chain.
Food chains are really all about energy. In a food chain, the same food doesn’t actually move from one living thing to the next. The food is turned into energy to help the animal that ate it to grow and maintain its own body. It is this growth that becomes the food for the next link in the food chain.
The arrows in a food chain show the direction in which the energy moves.
Not all energy from sunlight enters the food chain. Lots of it gets used in powering wind, waves and water evaporation. But the energy left over gets into plants. As it passes along the chain, a little more is used up at each stage. In fact, animals convert only about 10 per cent of their food energy into growth. The animal uses the rest just to stay alive.
End of the chain
Food chains rarely have more than five links. That is as many as the sun’s energy can power through living creatures. This is because most energy has been used up by the time it reaches the last one.
They usually end in a mammal or bird, which are both warm-blooded. Warm-blooded animals use up a lot of energy in generating enough heat to keep their bodies warm and working.