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Volume I · MMXXVI AP Environmental Science
Library› AP Environmental Science› Unit 1: The Living World: Ecosystems
⁂   AP Environmental Science · Unit 1

1. The Living World: Ecosystems

6–8% of the AP exam. 11 key topics. 4 common errors analyzed.

6–8% exam weight

Unit 1: The Living World: Ecosystems

Unit 1 (The Living World: Ecosystems) addresses environmental systems and human impacts. FRQs in this unit typically ask you to identify problems, propose specific solutions, and explain environmental consequences.

Key topics in this unit

  1. Ecosystem types and structure
  2. Terrestrial biomes (tropical rainforest, temperate deciduous forest, grassland, desert, tundra, taiga)
  3. Aquatic biomes (freshwater, marine, estuaries, wetlands)
  4. Biogeochemical cycles: carbon cycle
  5. Biogeochemical cycles: nitrogen cycle
  6. Biogeochemical cycles: phosphorus cycle
  7. Biogeochemical cycles: hydrologic (water) cycle
  8. Gross primary productivity (GPP) and net primary productivity (NPP)
  9. Trophic levels and energy flow
  10. Food chains and food webs
  11. Energy transfer efficiency (10% rule)

Common errors — what the rubric penalizes

These are the most frequently penalized mistakes on AP exam FRQs and MCQs. Review each before your next practice session.

Common error

Confusing GPP and NPP: students often forget that NPP = GPP minus the energy lost to plant respiration, not a separate measurement independent of GPP

Common error

Misapplying the 10% trophic energy rule by multiplying instead of dividing when moving up trophic levels, or applying it to biomass rather than energy

Common error

Treating biogeochemical cycles as independent when they are tightly coupled — for example, failing to connect the nitrogen cycle to eutrophication consequences in aquatic systems

Common error

Mixing up producers and decomposers in food web diagrams, particularly placing decomposers within a trophic chain rather than recognizing their cross-level role

Study checklist

  • Can you list all key topics from memory without this page?
  • Have you worked through at least one FRQ-style question per topic?
  • Can you explain each common error above — and why the correct answer differs?
  • Have you reviewed the relevant College Board CED section and formula sheet entries?
The Living World: Biodiversity →
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Our worked solutions and practice questions are original instructional content created by Tian2 AP. They are aligned to the concepts and skills described in College Board’s Course and Exam Description and are not reproductions of, or affiliated with, College Board’s official materials.