chapter3

Ecosystem boundaries

The limits or borders that define where one ecosystem ends and another begins, which can often be unclear.

Biosphere

The region of our planet where life resides; the combination of all ecosystems on Earth.

Photosynthesis

The process by which producers use solar energy to convert carbon dioxide and water into glucose and oxygen.

Cellular respiration

The process by which cells unlock the energy of chemical compounds.

Producer (Autotroph)

An organism that uses the energy of the Sun to produce usable forms of energy.

Consumer (Heterotroph)

An organism that is incapable of photosynthesis and must obtain its energy by consuming other organisms.

Trophic levels

The successive levels of organisms consuming one another in an ecosystem.

Gross primary productivity (GPP)

The total amount of solar energy that producers in an ecosystem capture via photosynthesis over a given time.

Net primary productivity (NPP)

The energy captured by producers in an ecosystem minus the energy producers respire.

Ecological efficiency

The proportion of consumed energy that can be passed from one trophic level to another.

Trophic pyramid

A representation of the distribution of biomass, numbers, or energy among trophic levels.

Biogeochemical cycle

The movements of matter within and between ecosystems.

Nitrogen fixation

The process that converts nitrogen gas in the atmosphere into forms of nitrogen that producers can use.

Denitrification

The conversion of nitrate into nitrogen gas, which is emitted into the atmosphere.

Phosphorus cycle

The movement of phosphorus around the biosphere.

Intermediate disturbance hypothesis

The hypothesis that ecosystems with intermediate levels of disturbance are more diverse than those with high or low disturbance levels.

Watershed

All land in a given landscape that drains into a particular stream, river, lake, or wetland.