AS91190 Earth and Space Science 2.4 - Organisms Surviving in an Extreme Environment
What this standard tests
AS91190 assesses how organisms survive in an extreme environment. You explain adaptations and link them to specific environmental stresses, using biological evidence rather than just describing the habitat.
Core rules and concepts
- Extreme conditions include high or low temperature, salinity, pressure, acidity, radiation, desiccation and low nutrients.
- Adaptations are inherited features that increase survival and reproduction. They can be structural, behavioural or physiological. Acclimatisation is a short-term adjustment, not an adaptation.
- Organisms may avoid the stress (migration, dormancy, shelter) or tolerate it (heat-stable enzymes, antifreeze proteins, modified membranes).
- Limiting factors and energy source matter: photosynthesis, chemosynthesis or consumed organic matter. Symbiosis can extend a host’s range.
Worked example
A cyanobacterial mat persists in a 70°C hot spring. Structural: the mat and biofilm reduce exposure and hold cells together. Physiological: heat-stable enzymes and membrane lipids maintain function at high temperature. Behavioural: cells reposition within the mat to balance light and heat. Ecological: heterotrophic microbes in the mat may consume oxygen and modify the local chemistry. Each trait maps to a named stress, and a test would compare growth at 50°C, 70°C and 85°C. Saying “it adapted to the heat” is not enough; the explanation must identify the mechanism and the evidence.
Traps that cost marks
- Calling acclimatisation an adaptation.
- Listing one trait as if it solves every stress.
- Ignoring trade-offs, such as heat stability reducing enzyme speed at low temperature.
- Using anthropomorphic language instead of mechanism.
- Describing the environment without linking each adaptation to survival.