Ecosystems Chapter 14

Pyramids of numbers = relative numbers of each organism at each trophic level

Numbers usually decrease - 90% of energy is used for growth, movement, some is excreted

These are the trophic levels of a pyramid of numbers.    However some pyramids of numbers can be irregular.

There are usually no more than  five trophic levels in a food chain.

Pyramids of biomass = quantity of biomass at each trophic level

Biomass is the total  dry quantity or weight of organisms.

Pyramids of biomass are always regular.

Compare:

The pyramid of numbers is unbalanced and the pyramid of biomass is balanced.

Only around  10% of the energy is transferred to the next trophic level.

Key terms

Producers - plants which photosynthesise to produce food.

Consumers - Animals that eat plants and/or other animals.

Decomposers - Organsims that decay dead material and help to recycle nutrients.

Physical Environment - the sum total of non-biological components in an eco-system - e.g. water

Ecosystem - A distinct, self-supporting system of organisms interacting with each other and their physical environment

Population - All the organisms in a particular species living in an eco-system at any particular time

Community - All the populations of living organisms in an eco-system at any particular time

Habitat - A place where specific organisms live - their home

Quadrats - used to sample the distribution of organisms, or estimate the population size of an organism

1. Heat from sun à evaporation (water) + transpiration (plants) à Water vapour in the air

2. Water vapour à  condensation (clouds) 

3. Clouds à precipitation (rain/snow) [when clouds go over high ground - air cools]

4. Water à run-off into streams + absorbed by plants

5. Run off à  lakes and seas

6. Starts again