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Date November 2019 Marks available 2 Reference code 19N.3.HL.TZ0.17
Level Higher level Paper Paper 3 Time zone TZ0 / no time zone
Command term Outline Question number 17 Adapted from N/A

Question

The figure below shows the effects of soil pH on nutrient availability. Thicker bars indicate higher nutrient availability.

[Source: diagram drawn from Emil Truog, 1947, The Liming of Soils, USDA Yearbook of Agriculture 1943–1947,
and N.A. Pettinger, 1935, A Useful Chart for Teaching the Relation of Soil Reaction to the Availability of Plant
Nutrients to Crops, Virginia Cooperative Extension, Virginia Tech, and Virginia State University]

 

Identify which element is more available in strongly acid conditions.

[1]
a.

Outline the roles of Rhizobium bacteria in the nitrogen cycle.

[2]
b.

Describe the major characteristics of a eutrophic lake.

[2]
c.

Markscheme

iron/Fe ✔

a.

a. «Rhizobium» forms mutualistic/symbiotic relationship with roots/legumes ✔

b. «Rhizobium» fixes «atmospheric» nitrogen ✔

c. converts it into ammonia «to be used by plants» ✔

b.

a. normally shallow ✔

b. low water visibility
OR
high levels of nutrients/phosphates/potassium
OR
low oxygen concentration
OR
high BOD ✔

c. high net primary productivity
OR
algal bloom
OR
low biodiversity ✔

c.

Examiners report

[N/A]
a.
[N/A]
b.
[N/A]
c.

Syllabus sections

Option C: Ecology and conservation » Option C: Ecology and conservation (Additional higher level topics) » C.6 Nitrogen and phosphorus cycles
Option C: Ecology and conservation » Option C: Ecology and conservation (Additional higher level topics)
Option C: Ecology and conservation

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