Key Idea: Topic 2.1 explains how we define and classify life, how we identify organisms, and why populations are found where they are (because of abiotic + biotic limiting factors and tolerance ranges).
✅ Must-know definitions
🧬 Classification (why it matters)
🔍 Identification (field skills)
Evaluation question? Give one strength + one limitation of dichotomous keys, with a short example (e.g., damaged wing spots).
👥 Populations (exam favourite)
🌡️ Abiotic vs biotic limiting factors
Abiotic (non-living): Temperature (enzyme activity/metabolism). Light (photosynthesis). Water availability (all life processes). pH (enzyme function). Salinity (freshwater vs marine tolerance).
Biotic (living): Producers / consumers / decomposers. Predation. Competition. Disease / parasites.
The most limiting factor is the one that has the greatest effect on population size or distribution.
📈 Tolerance curves (range of tolerance)
Graph questions: read optimum from the peak x-value, then give the tolerance range, and identify stress vs lethal zones.
1) Define species (include fertile offspring). 2) Define population (same species/area/time). 3) Name 3 abiotic + 2 biotic factors. 4) Label a tolerance curve.