C4.2 Transfers of Energy and Matter

Open system

A system where resources can enter or exit, including both chemical substances and energy

Closed system

A system which only allows an exchange of energy

Sunlight

The principal and initial source of energy that sustains most ecosystems. It is needed to produce glucose in photosynthesis

Photosynthesis

Carried out by cyanobacteria, plants, and eukaryotic algae

Bacteria

The main source of energy in the deep sea. They use sulfides as a source of energy

Energy

Enters as light, flows as nutrients through the food chains, and usually leaves as heat

Examples of recycled nutrients

Carbon, nitrogen, and phosphorus

Primary consumers

Herbivores

Secondary consumers

Carnivores

Decomposers

They are supplied with energy from carbon compounds in dead organic matter, such as faeces, dead plant material, and shed exoskeletons

Food chain

A model that shows the flow of energy through a sequence of organisms, each of which feeds on the previous one

Food web

A model that summarises all of the possible food chains in a community

Saprotrophs

They secrete digestive enzymes into the dead organic matter and digest it externally. They then absorb the products of digestion, including sugars and amino acids

Photoautotrophs

Organisms that carry out photosynthesis (eg. plants, eukaryotic algae, cyanobacteria)

Chemoautotrophs

Organisms that take inorganic chemicals and transform it into energy (eg. prokaryotic bacteria)

Autotrophs

Organisms that can produce their own food using light, water, carbon dioxide, or other chemicals

Heterotrophs

Organisms that eat other plants or animals for energy and nutrients

ATP

The source of energy for use and storage at the cellular level. In both autotrophs and heterotrophs, it is produced by cell respiration

Trophic level

The relative position of an entity in the food chain. Energy is lost between them, limiting the number of levels

Energy pyramids

A model that shows the flow of energy from one trophic level to the next

Energy transfer percentage

10%

Incomplete consumption

The organisms in a trophic level are not entirely consumed by organisms in the next trophic level, causing a loss of energy

Incomplete digestion

Not all parts of food ingested by organisms are digested and absorbed, the indigestible material is egested in faeces. Energy in faeces does not pass on along the food chain

Cell respiration

A process that all living things use to convert glucose into energy. The waste products, carbon dioxide and water, do not supply energy to the next trophic level

Biomass

A measure of the total mass of a group of organisms within one trophic level.

Gross primary production (GPP)

The total biomass of carbon compounds made in plants by photosynthesis

Net primary production (NPP)

GPP minus the biomass lost due to the respiration of the plant. This is the amount of biomass available to consumers

Secondary production

The accumulation of carbon compounds in biomass by animals and other heterotrophs (consumer level)

Carbon sink

When photosynthesis exceeds respiration (more carbon dioxide absorbed than released)

Carbon source

When respiration exceeds photosynthesis (more carbon dioxide released than absorbed)

Carbon

Found in pools: Biosphere, hydrosphere, atmosphere, sediments

Pool

A reserve of the element, it can be organic or inorganic

Flux

The transfer of the element from one pool to another

Three main types of carbon flux due to living organisms

Photosynthesis, feeding, respiration

Keeling curve

Shows two trends: Annual fluctuations and long term trend

Quaternary consumers

Top of the food chain

Carbon, hydrogen, and oxygen

Needed to make carbohydrates, lipids, and other carbon containing compounds

Nitrogen cycle

The recycling phase of the nitrogen which includes nitrogen fixation, ammonification, nitrification, and denitrification