DP Biology (first assessment 2025)

Test builder »

Question 20N.2.SL.TZ0.c

Select a Test
Date November 2020 Marks available [Maximum mark: 7] Reference code 20N.2.SL.TZ0.c
Level SL Paper 2 Time zone TZ0
Command term Explain Question number c Adapted from N/A
c.
[Maximum mark: 7]
20N.2.SL.TZ0.c

Explain the transformations of carbon compounds in the carbon cycle.

[7]

Markscheme

a. autotrophs/producers convert carbon dioxide into carbohydrates/carbon compounds in photosynthesis;

b. carbon dioxide diffuses/moves from the atmosphere /water into autotrophs/plants;

c. carbon compounds are transferred through food chains/OWTTE;

d. carbon dioxide produced by respiration diffuses out of organisms into water/atmosphere;

e. decomposers release carbon dioxide during decay/putrefaction;

f. methane is produced from organic matter in anaerobic conditions (by methanogens);

g. some methane diffuses into the atmosphere/accumulates in the ground;

h. methane is oxidized to carbon dioxide (and water) in the atmosphere;

i. peat forms when organic matter is not fully decomposed because of acidic/anaerobic conditions in waterlogged soils;

j. partially decomposed organic matter from past geological eras/fossils was converted into coal/oil/gas that accumulated in rocks;

k. carbon dioxide is produced by the combustion of biomass/fossilized organic matter/fuels;

i. hard parts of some animals/corals/molluscs are composed of calcium carbonate

m. can become fossilized in limestone;

As this is an “explain” question, simply drawing a labelled diagram is not enough for [7]. Diagram would need sufficient annotations to meet the command term.

If carbon compounds are referred to instead of carbon dioxide, penalise once then ecf.

Syllabus sections