DP Biology (first assessment 2025)

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Question 22N.2.SL.TZ0.a

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Date November 2022 Marks available [Maximum mark: 4] Reference code 22N.2.SL.TZ0.a
Level SL Paper 2 Time zone TZ0
Command term Outline Question number a Adapted from N/A
a.
[Maximum mark: 4]
22N.2.SL.TZ0.a

Outline how energy flows in an ecosystem.

[4]

Markscheme
  1. energy from the sun is captured by plants/autotrophs;
  2. light energy is converted to chemical energy by photosynthesis;
  3. energy is passed to animals/consumers/along the food chain;
  4. at each stage in the food chain energy is lost by respiration/as heat;
  5. much less energy/only about 10 % is available at each stage/trophic level of the food chain;
  6. some energy is made available to decomposers when organisms die/parts fall to the ground;
  7. energy cannot be recycled;
Examiners report

Explaining the energy flow in part (a), was one of the best answered questions on the paper. However, the 
conversion of light energy to chemical energy was missed by many. Some weaker candidates are still confusing energy with biomass, and lost marks due to contradictory statements such as saying that in the end the energy goes into the soil and is taken up by the plants again.

In both (a) and (b) many students drew diagrams, Carbon cycles etc. Some of these aided the explanation, but the majority contributed nothing.

Syllabus sections