IB Environmental systems and societies Topic 2: Ecology Key Definitions

Abiotic factors are the non-living physical and chemical elements, such as temperature, sunlight, and soil composition.

Ammonification (a type of decomposition) converts organic nitrogen (e.g., amino acids, urea) into ammonia or ammonium ions.

Body structures that look or work alike in different species but evolved independently under similar pressures, not from a common ancestor. They are not evidence of close relationship.

Autotrophs are organisms that can synthesize their own food from inorganic sources of carbon (typically carbon dioxide, CO₂) and other essential elements.

Bioaccumulation refers to the process by which the concentration of non-biodegradable pollutants increases in an organism over time.

Biogeochemical cycles are the natural pathways through which essential elements like carbon, nitrogen, and phosphorus circulate between the biotic (living) and abiotic (non-living) components of Earth.

Biomagnification refers to the process by which the concentration of non-biodegradable pollutants increases as you move up trophic levels in a food chain or food web.

Biomass is the total mass of living organisms in a given area or volume.

A biome is a group of ecosystems that share similar climatic conditions, regardless of their geographic location.

The biosphere is the global ecological system that includes all living organisms and their interactions with the atmosphere, hydrosphere, and lithosphere.

Biotic factors are the living components of an ecosystem, such as plants, animals, and microorganisms, as well as their interactions.

Species with traits between r-strategists and K-strategists, combining fairly rapid reproduction with moderate parental care and competitive ability. They often dominate mid-successional stages.

Carbon sequestration is the process of capturing atmospheric carbon dioxide (CO₂) and storing it in solid or liquid form.

Carrying capacity is the maximum number of individuals of a species that an environment can sustainably support over time.

Cellular respiration is the conversion of stored chemical energy in glucose into a usable chemical form that fuels metabolic processes in living cells.

Chemoautotrophs are organisms that use inorganic chemical reactions to obtain energy, typically through exothermic reactions, to drive the process of chemosynthesis.

A clade is a group of organisms that includes a common ancestor and all its descendants.

Cladistics is the branch of biology that classifies organisms according to their evolutionary relationships, not just physical similarities.

Classification is the systematic arrangement of organisms into groups based on shared characteristics.

Climate describes the average weather conditions in a region over a long period, typically 30 years or more.

A climax community is the final, stable community in succession, in equilibrium with its environment and characterized by high biodiversity, complex food webs, and efficient nutrient cycling.

A community is a collection of interacting populations of different species living in the same area and at the same time.

Competition occurs when two or more organisms require the same limited resource, resulting in a negative effect on all participants’ growth, survival, or reproduction.

If two species compete for exactly the same limited resources, one will always be the better competitor, so the two cannot occupy the same niche indefinitely. The weaker competitor is eliminated from that niche.