Ecosystems 3

Biomass

The total mass of living material in a specific area at a given time. Usually measured in gm-2. Fresh mass is quite easy to assess

Calorimetry

The chemical energy store in a dry mass can be estimated using this technique. When a sample of dry material is weighed and then burnt in pure oxygen within a sealed container (bomb). The bomb is surrounded by a water bath and the heat of combustion causes a temperature rise. This can be used to work out the energy released from the mass of burnt biomass.

Producer

Photosynthetic organism that manufacture organic substances using light energy

Consumer An organism that obtains its energy by feeding on (consuming) other organisms. Primary consumers eat producers. Secondary consumers eat primary consumers. Tertiary consumers eat secondary consumers.

Extracellular digestion

When saprobionts release enzymes externally which break down large biological molecules into smaller ones which are then absorbed by digestion or active transport.

Trophic level

Each stage in a food chain

GPP

Gross primary production which is the total quantity of the chemical energy store in plant biomass

NPP

Gross primary production – respiratory losses. The chemical energy store which is left when these losses to respiration have been taken into account. This is available for plant growth and reproduction and available to other trophic levels in the ecosystem (such as consumers and decomposers).

Respiratory losses

Taken away from GPP to calculate NPP.

Food chain

Describes a feeding relationship in which the producers are eaten by primary consumers

Food web

How food chains link together in a habitat to form a food web.

Pyramid of number

A pyramid drawn with bar lengths proportional to the numbers of organisms present

Pyramid of biomass

A pyramid drawn with bar lengths proportional to the mass of plants/animals

Pyramid of energy

A pyramid drawn with bar lengths proportional to the energy stored in organisms

Productivity

The rate of generation of biomass in an ecosystem. Usually measured in units of mass per area put unit time (gm-2y-1). Farming practices try to improve this by increasing yields by increasing the efficiency of energy transfer along the food chains which produce our food.

Intensive farming

A type of farming which uses processes

Percentage efficiecy

Can be calculated by dividing the energy available after the transfer by energy available before the transfer x 100.

Energy transfer

(Energy available after the transfer / energy available before the transfer) x 100

Biological control

Controlling pests by introducing predators

Selective breeding

Breeding of organisms by human selection of parents for certain characteristics