Biology › Ecology, populations and environmental change

Ecology, populations and environmental change

Unit B20 · 5 lessons.

Notes

Illustrated notes for each topic in this unit, with worked examples and a checklist of objectives.

• Populations and their limits
  Population, community and habitat as separate terms; the sigmoid growth curve and its lag, log, slowing and stationary phases; carrying capacity…
• Nutrient cycles: nitrogen, phosphorus and eutrophication
  Why nitrogen matters and why nitrogen gas is useless to plants; the four bacterial processes of the nitrogen cycle, which are nitrogen fixation…
• Succession and environmental change
  Primary and secondary succession; pioneer species and the changes they make to the abiotic environment; seral stages and the climax community; how…
• The carbon cycle and climate change
  The carbon cycle assembled from photosynthesis, respiration, decomposition and the exchange between air and sea, with fossil fuels as a store of…
• Managing ecosystems sustainably
  Sustainable yield read off the logistic growth curve, and why the largest catch a population can replace comes at about half the carrying capacity.

Practical work

The practical capabilities this unit's work belongs to, each with its techniques, its calculations and the errors that cost marks.

• Field sampling, distribution and behavioural response