Background reading · Science
Food chains: following the energy
Every food chain starts with the Sun, and most of the energy is lost at each step.
Plants and algae are producers. They use sunlight to make food by photosynthesis. Everything else is a consumer: it gets energy by eating something else.
Arrows show the energy
In a food chain the arrow points from the food to the feeder: algae → mayfly larva → kōaro (a native fish) → shag. The arrow shows where the energy goes.
Why chains are short
At each step most of the energy is used for moving, growing and keeping warm, or is lost as heat. Only about a tenth passes on to the next feeder. That is why there are far more plants than plant-eaters, and far more plant-eaters than top predators.
Webs, not chains
Real ecosystems are food webs: most animals eat several things and are eaten by several others. If one link disappears, for example when a weed shades out the algae, the change ripples through the whole web.
People are part of the web
Clearing bush, adding fertiliser, introducing predators and removing weeds all change food webs. Your investigation is about finding out which changes matter most in your place.
Sources and further reading
Written for Kōkiri Learn students in our own words. Check facts against the sources.