1.3 Energy and Equilibria

Energy enters (most) ecosystems from the sun. The amount of energy that is available to each organism decreases along the food chain due to losses at each trophic level. When we describe energy as lost, it is never “used up” or destroyed, but only transformed into other (less useful) forms.

Ecosystems can exist in a state which is not constant but stable in a state of dynamic equilibrium, maintained by negative feedback mechanisms.


1Energy in an ecosystem
2Positive and negative feedback
3Equilibrium, resilience and tipping points
Chapter Workbook
Vocabulary Sheet

  • (None for this chapter)

Full PSOW here.

Essay Task

“Explain the factors that determine the resilience of an ecosystem and describe scenarios that could push an ecosystem beyond a tipping point.” [9 marks]

View essay markbands

The essay should marked using the Paper 2, Section B essay markbands.

PDF Version

Google Docs Version

Google Docs 1.3 essay

Open the link and make a copy to your own drive. The doc can easily be shared as an “Assignment” on Google Classroom.

A markbands rubric designed for Google Classroom is available here.