IB Biology Topic D4.2: Sustainability and Change Key Definitions

Biochemical Oxygen Demand (BOD) measures the oxygen required by microorganisms to decompose organic matter.

Biomagnification is the increase in toxin concentration at each successive trophic level in a food chain.

A climax community is a stable, mature ecosystem that has reached equilibrium with its environment.

Cyclical succession is a type of ecological succession where ecosystems repeatedly cycle through a series of stages.

Ecological succession describes the process of gradual changes in species composition and abiotic factors in an ecosystem over time.

Ecosystem stability is the ability of an ecosystem to maintain structure and function over time, even when faced with disturbances like climate change, natural disasters, or human activity. High biodiversity plays a critical role in promoting this stability.

Eutrophication is a process that occurs when a body of water becomes enriched with nutrients, which causes excessive plant and algae growth

Fertilizers refer to natural or artificial substance containing the chemical elements that improve growth and productiveness of plants

A greenhouse gas is a gas that contributes to the greenhouse effect by absorbing infrared radiation

A species whose effect on its ecosystem is disproportionately large relative to its abundance or biomass. Removing it produces large changes in community structure and function.

Leaching refers to the loss of water soluble plant nutrients from the soil due to rain and irrigation.

Large, visible debris such as fishing nets and ropes, plastic bottles, caps, and grocery bags.

Mesocosms are controlled experimental systems that replicate natural ecosystems, allowing scientists to study how variables like nutrient cycling and energy flow affect stability.

Plastic fragments smaller than 5 mm in size.

pH is a measure of how acidic or basic a solution is, ranging from 0 (very acidic) to 14 (very basic).

Primary succession is the process by which life gradually colonizes and transforms a previously uninhabitable area.

Rewilding is the process of restoring ecosystems to their natural state by reducing human interference and reintroducing key species to allow nature to recover.

Soil erosion is a gradual process of movement and transport of the upper layer of soil (topsoil) by different agents – particularly water, wind, and mass movement – causing its deterioration in the long term

A tipping point is the critical threshold where a small change in conditions (like temperature or moisture) causes a dramatic shift in an ecosystem.

Transpiration is the loss of water vapor from the aerial parts of a plant, primarily through tiny pores in the leaves called stomata.