Biology - Section D: Ecology and Environment

Ecosystems

An ecosystem is a self-supporting system of organisms interacting with each other and their environment. The population size of the organisms in an ecosystem is affected by the physical environment such as temperature, amount of rainfall and amount of sunshine. 

Plants are named producers because the produce food by photosynthesis. Animals are named consumers because they eat plants and other organims to get their energy and bacteria and fungi are named decomposers because the break down and decompose dead material and waste products.

Feeding Relationships

Food chains are used to show feeding relationships. They always start with a producer. 

Grass ----> Grasshopper ----> Lizard

Plankton ----> crustacean ----> fish ----> seal ----> polar bear

Many food chains over lap to form a foodweb however both food chains and foodwebs over simplify the situation. They do not tell you the numbers or mass of organisma involved and they do not show the role of decomposers. 

Ecololgical Pyramids

• Pyramids of Numbers represents the numbers of organisms at each trophic leel in a food chain. They have many limitations and for example a tree can…