Food webs and ecosystem interactions

You are here

Food webs and ecosystem interactions

Trophic levels can also be described as food chains or energy chains. When a food chain is taken to its natural conclusion, humans are found at the end of it, meaning that we are dependant on an efficient transfer of energy along a food chain. Every link in the chain acquires food and feeds on the link prior to it. Each link is also consumed by the link that follows it, for example, blackbirds eat green plants, but in turn are eaten by tertiary consumers such as hawks. Food chains are the process whereby energy that is trapped in carbon compounds is transferred through an ecosystem.

A simple food chain is unlikely to be found within an ecosystem and a more complex food web is more common, as shown in the diagram below:

Food webs and ecosystem interactions

Food webs exist because as shown in the above diagram there is a wide variety of consumers operating at each level. In addition animals such as foxes eat plants and animals, meaning they cannot be placed solely on one category.

The transfer of energy through an ecosystem is in one direction, where light energy from the sun becomes heat energy, is fixed in plants via photosynthesis, and then lost as it moves through subsequent trophic levels. The movement of both materials (chemicals) and nutrients within an ecosystem is different.

The diagram below shows the main parts of the nitrogen cycle. Protein is synthesized from inorganic compounds found in the soil or free nitrogen in the air. This process is helped by nitrogen fixing bacteria in the soil. Certain bacteria have a symbiotic (beneficial) relationship with other plants. A smaller organism (symbionant) usually lives on the host (larger organism).

Food webs and ecosystem interactions

Chemicals are an important part of an ecosystem, as they are needed to produce organic material that is moved around the ecosystem and continually recycled. Examples include both carbon and nitrogen, which are absorbed by plants as gases and salts. The gases come from the atmosphere and the salts come from the soil. At the basic level in each cycle plants take up chemical nutrients, utilize them and then forward them to herbivores and then carnivores.

S-cool exclusive FREE TUTORIAL offer!