A Food Web

Here's a food web of some of the species that live in the Great Barrier Reef. A food web is a diagram that shows the transfer of energy in an ecosystem. For example, the fish eats the algae, so it gains the energy contained in the algae. This specific food web doesn't include all of the organisms living in the Reef, but it helps to get a general idea. 

When you look at a food web, it's important to understand trophic levels. A trophic level is a position that an organism occupies in a food chain. The first trophic level is the producer. In this diagram, the producers are the algae and the seagrass. Producers are organisms that can do photosynthesis to produce their own food. The second trophic level is the consumers. These consumers consist of the organisms that eat the producers. In this diagram, those are fish, sea turtles, and dugongs. The third trophic level, aka. the secondary consumers consist of the animals that eat the first level of consumers. In this case, the secondary consumers are the white-bellied sea eagles, the dolphins, and the sea snakes. Finally, the fourth trophic level, tertiary consumers, are the ones that eat the lower level consumers. In our diagram, this is the tiger shark. It's cool to think that at each level of the food chain, there is a transfer of energy and that originally, all of this energy came from the sun!

Click here to learn more about the flow of energy in an ecosystem.

Sources: Wikipedia, Scitables