Environmental Systems and Societies · Topic 2: Ecology

ES2.2 — Energy and biomass in ecosystems

Environmental Systems and Societies · SL / HL · syllabus-mapped notes

1. The laws of thermodynamics and two key processes

   Energy and matter as ecosystem inputs, the first and second laws, and how photosynthesis and cellular respiration transform them.

2. Producers, consumers and food chains

   Autotrophs and heterotrophs, the range of consumer strategies, and how energy and biomass flow along food chains and webs.

3. Energy losses, productivity and ecological pyramids

   Why transfer is never complete, gross and net productivity, the 10% rule, measuring biomass, and pyramids of number, biomass and energy.

4. Pollutants and human impacts on energy flow

   Bioaccumulation and biomagnification, microplastics as carriers, and how fossil fuels, deforestation, urbanization and agriculture disrupt flows.

5. HL: Chemoautotrophs and measuring productivity

   Photoautotrophs versus chemoautotrophs, and defining and measuring primary and secondary productivity from lab and field data.

6. HL: Sustainable yield, efficiency and entropy

   NPP as the basis for food chains, maximum sustainable yields, ecological efficiency calculations, and entropy in ecosystems.