Science Focus Topic 4 Notes: How Organisms Interact | Print |

Living organisms make up the biotic components of the ecosystem, while non-living things make up the abiotic parts of the same ecosystem.

The Roles of Organisms in an Ecosystem

All of the organisms within an ecosystem have different roles. These roles are called niches. Organisms can have more than one niche and knowing the niches of an organism can help to explain why they act and interact the way they do. To determine an organism's niche, you need to identify what it eats, where it lives and how it interacts with the other organisms in the same ecosystem.

Niches include:

  • Producers - produce food energy for themselves and others
  • Consumers - consume the food made by the producers
  • Herbivores - eat producers (plant eating niche)
  • Carnivores - eat other consumers (meat eating niche)
  • Predators eat prey
  • Omnivores - eat both producers and consumers

Food Chains

A food chain is a model that shows how energy stored in food passes from organism to organism.

Energy flow is the movement of energy, starting with the sun, and passing from one organism to another.

As energy flows from one organism to another
a food chain is established. Food chains usually involve more than three organisms.

Food Webs
A food web is a combination of many different food chains, showing the interrelationships between and amony many difeerent producers and consumers in an ecosystem.

Food Pyramid is a model representing the numbers of organisms consumed at each successive level of the pyramid. The size of the level indicates the number of organisms at that level. There are always more animals being eaten than are eating.
To find out how much energy is being transferred from one level of the pyramid to the other, Biomass needs to be calculated. Biomass is the total of all the organisms in the ecosystem. As you move up the pyramid, there is less biomass. The most biomass is found at the base, where the producers are.

The Clean-Up Squads:
Scavengers are organisms that feed on dead or decaying plant or animal matter.




Decomposers are different from scavengers because they do not actually eat dead material. They grow on or in the dead or waste matter, absorbing the nutrients directly into their cells, which are then recycled back into the environment.