Food chains, sampling and cycles

The idea

Food chains begin with a producer that makes glucose by photosynthesis, followed by primary, secondary and tertiary consumers. Quadrats and transects are used to sample organisms: estimated population = mean number per quadrat × (total area ÷ quadrat area). Materials are recycled: microorganisms decompose dead matter, returning carbon dioxide and mineral ions. The water cycle and carbon cycle move materials through living and non-living parts.

1. Place quadrats randomly to avoid bias.
2. Find the mean per quadrat.
3. Scale up to the whole area.

Watch out A transect shows how a population changes across an area; random quadrats estimate the total population.