standard Grade Biology - topic one : Biosphere

  • Created by: Bethany
  • Created on: 08-10-11 15:55

How it works

  Habitat The place where an organism lives

Population All of the members of one species living in an area

Community All the living things, animals and plants, living in a particular habitat

Ecosystem Habitat + Community

Producer An organism that can make its own food e.g. green plants change light energy into chemical energy (food) by the process of photosynthesis. All food chains start with a producer.

Consumer An organism that must eat other organisms to get energy. All animals are consumers.

Food Chain A simple diagram showing the feeding relationship between organisms in a habitat.

Floating algae → Water fleas → Minnows

Food Web A complex diagram showing the interconnecting food chains in a habitat.

→ Shows the direction of energy flow in a food chain/web

Producer a green plant that makes its own food by photosynthesis

Consumer an organism that can not make food and so needs to feed on another organism

Biomass the total mass of organisms at each stage of a food chain C

ompetition when two organisms need the same resource

Recycling where a nutrient such as nitrogen is used over and over again


Here is an example of part of a food web in a Scottish loch.

Food web. The arrows show the direction of energy flow. (

If one species is lost from a food web all the others are affected. In the web above, if the mosquito larvae were removed the ducks will have less food and the floating algae will be eaten less. So the duck population is likely to decrease and the floating algae population may increase.

Other populations will also be affected. For instance, the water flea population might be expected to increase as there will be more floating algae to eat. The snails do not appear to have any connection to the mosquito larvae, and yet their population may decrease if the hungry ducks eat more of them.

Energy Loss form a Food Chain/Web

Energy is lost at each stage of a food chain or web. This is due to the organisms using some of the energy they get to survive. Energy is lost from food chains/webs because the organisms need to:

  • move
  • heat
  • reproduce
  • carry out chemical reactions

The energy that is passed on is that from growth. The bigger the organism eaten the more energy the next organism can get.

Pyramids of Numbers and Biomass

A pyramid of numbers (a diagram to show the numbers of organisms within a food chain or web) shows the relative number of organisms at each stage of a food chain.

Here is an example of a food chain:

Grass Plant (producer)  → Vole (primary consumer)  → Barn owl (secondary consumer)

The pyramid of numbers for this food chain would look like this:

Food pyramid which consists of grass plant at the bottom of pyramid, above this is the vole, and at the top is the barn owl. (

Pyramid of Biomass

Sometimes a pyramid of numbers is not the best way…


No comments have yet been made

Similar Biology resources:

See all Biology resources »