Ecosystems & Biodiversity is a core part of IB Environmental Systems. Revise the key concepts and common mistakes below, then lock them in with the free games.
BiomeLarge geographic region with characteristic climate, vegetation, fauna; e.g., tropical rainforest, tundra.
ProducersAutotrophs (mostly plants/algae) converting solar to chemical energy via photosynthesis.
Trophic pyramidStepped diagram of energy/biomass at each level; pyramid of energy always upright.
Gross/Net productivityGPP = total energy fixed; NPP = GPP minus respiration; available to higher trophic levels.
Carbon cycleC moves through atmosphere, oceans, biomass, soils; fluxes altered by fossil fuel combustion.
Nitrogen cycleN2 fixation (Rhizobium), nitrification (Nitrosomonas), denitrification (Pseudomonas); fluxes doubled by Haber-Bosch.
BiodiversityVariety of life: genetic, species, ecosystem (term popularised by Wilson 1988).
IUCN Red ListCategorises species: LC, NT, VU, EN, CR, EW, EX; founded 1964 by International Union for Conservation of Nature.
Edward O. WilsonHarvard biologist; theory of island biogeography (with MacArthur 1967); biophilia hypothesis 1984.
Habitat fragmentationContinuous habitat divided into smaller patches; reduces connectivity, edge effects, genetic flow.
Sixth mass extinctionCurrent human-caused extinction crisis; rates 100-1000x background (Ceballos et al. 2015 PNAS).
Convention on Biological Diversity1992 Rio treaty; targets in Aichi 2010 and Kunming-Montreal 2022 (30x30 by 2030).
Questions where students often pick the tempting wrong answer — make sure you know the right one: