2.2 Energy and biomass in ecosystems

Food chain

A simple linear sequence showing the flow of energy through organisms by feeding

Food web

A complex network of interconnected food chains showing multiple feeding relationships.

Producers (autotrophs)

Organisms that convert solar energy into chemical energy via photosynthesis.

Consumers (heterotrophs)

Organisms that obtain energy by eating other organisms

Decomposers

Break down dead organic matter and recycle nutrients into the ecosystem

Productivity

The rate at which biomass or energy is produced per unit area per unit time

Gross Primary Productivity (GPP)

The total energy captured by producers via photosynthesis

Net Primary Productivity (NPP)

The energy available to consumers after plant respiration.

NPP = GPP - R

Gross Secondary Productivity (GSP)

The total energy assimilated by consumers

Food eaten - fecal lost

Net Secondary Productivity (NSP)

The energy available for growth and reproduction in consumers after respiration losses.

NSP = GSP - R

Trophic efficiency

The percentage of energy transferred from one trophic level to the next

(energy at higher trophic level)/(energy at lower trophic level) x 100

Pyramid of numbers

Shows the number of organisms at each trophic level

Pyramid of biomass

Shows total dry mass of organisms at each level

Pyramid of energy

Shows energy content at each trophic level