Topic 2 – The Ecosystem

California redwoods, John Muir Woods, USA

California redwoods, John Muir Woods, USA (photo credit: author)

Topic 2 – The Ecosystem covers the essentials of ecology: the structure and function of ecosystems and biomes around the world, the living and non-living characteristics of those systems, and measurements of those characteristics. Some of the most important internal assessments (IAs) we carry out in ESS will focus on one of the components of ecosystem science.

“Chapter 3 – The Ecosystem” in the ESS Course Companion corresponds with the material in Topic 2. It’s a long chapter, so read it thoroughly more than once, and make sure you take note of all the key words and case studies.

Objectives (Students will be able to…)

  • Distinguish between biotic and abiotic (physical) components of an ecosystem, including trophic levels in food chains and food webs selected from the local environment.
  • List, describe and evaluate methods for measuring abiotic (physical) factors within an ecosystem.
  • Discuss how pyramids of numbers, biomass, and productivity affect the functioning of an ecosystem.
  • Construct and use dichotomous keys to identify, describe, and evaluate the biomass of trophic levels in a community.
  • Define biome and explain the distribution, structure and relative productivity of tropical rainforests, deserts, tundra and any other biome.
  • Describe and explain the transfer and transformation of energy and matter in ecosystems, through photosynthesis, respiration, producers, consumers, and decomposers.
  • Describe and evaluate the factors regulating change within ecosystems, including populations, energy, productivity, and succession.
  • Describe and evaluate methods for measuring changes in abiotic and biotic components of an ecosystem due to specific human activity along an environmental gradient.

 Resources and Notes

ESS Topic 2.2 – Measuring Abiotic Components of the Ecosystem

  • The video below describes the line transect method used to monitor animal populations.

  • ESS Topic 2.4 – Biomes
    • Terrestrial Biomes – This page from The Knowledge Project at has a ton of excellent information linking temperature and precipitation patterns tothe distribution of terrestrial biomes and the diversity of organisms living in each one.
    • Biomes Matrix.pdf – This document summarizes the climate, distribution, structure, and productivity of the world’s major terrestrial biomes.
    • There are 2 biome presentations below, which I found on, and they cover all the major terrestrial biomes on Earth.

Click on the image below for an animation of secondary succession in a bog forest.

 Animation & image source:

Animation & image source:


Of Interest…