IB Biology Topic C4.2: Transfer of Energy and Matter Key Definitions

An autotroph is an organism that uses external energy sources to synthesize carbon compounds from simple inorganic substances.

An ecosystem that absorbs more carbon than it releases.

An ecosystem that releases more carbon than it absorbs.

Cell respiration is a series of metabolic processes that convert energy stored in carbon compounds, such as glucose and fatty acids, into ATP.

The process by which certain organisms (like sulfur bacteria) use energy from inorganic molecules (such as hydrogen sulfide) to produce food in the absence of sunlight.

A system that only exchanges energy with its surroundings, not matter.

Decomposers are organisms that break down dead organic matter, releasing energy and nutrients back into the ecosystem.

An ecosystem is an ecological unit consisting of living organisms (biotic components) interacting with their physical environment (abiotic components).

The process by which the plasma membrane pinches inward to form a vesicle that brings external materials into the cell.

A food chain is a linear sequence of organisms, each feeding on the previous one, illustrating the flow of energy and nutrients in an ecosystem.

A food web is a complex network of interconnected food chains, representing all the feeding relationships within a community.

Organisms that obtain energy and carbon by consuming other organisms or organic matter.

Lignin is a complex, strong polymer deposited in the walls of xylem vessels.

A system that exchanges both energy and matter with its surroundings.

Primary production refers to the synthesis of organic carbon compounds from carbon dioxide by autotrophs, such as plants and algae, using external energy sources like sunlight.

Secondary production is the accumulation of carbon compounds in biomass by animals and other heterotrophs, which ingest food and build these compounds into proteins and other macromolecules.

A trophic level represents a group of organisms that share the same position in a food chain, based on how they obtain energy.