IB Biology SL B4.1.3 Abiotic Variables Affecting Distribution Questions

Explore how temperature, pH, light, moisture and other abiotic gradients limit organisms and shape distribution, abundance and cover in IB Biology SL B4.1.3.

Exam points

Identify temperature, salinity, pH, light, rainfall, humidity, moisture, wind, substratum, nutrients or carbon dioxide as abiotic variables and explain how deficiency or excess can limit survival, growth or reproduction.
Relate a named abiotic variable such as temperature, pH, light or moisture to changes in species distribution, abundance or cover using data, graphs or ecological examples.
Use a transect or other field method to measure an abiotic gradient and correlate it with the distribution or abundance of organisms.

[Maximum number: 2]

The tundra ecosystem in Finnish Lapland has a short growing season and a mean temperature of $-2.0^{\circ} \mathrm{C}$ . It is also naturally grazed by herbivores such as reindeer (Rangifer tarandus). Different quadrats were set up to include and exclude the reindeer in both normal and warmed temperatures. Open-topped warming chambers were used to heat both the soil and air in the warmed quadrats. The graph shows the changes in plant richness over five years.

Figure for Question IB Biology SL B4.1.3 Abiotic Variables Affecting Distribution Questions question 1 — IB Biology SL

Identify two abiotic limiting factors on plant growth in a tundra ecosystem.

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IB Biology SL B4.1.3 Abiotic Variables Affecting Distribution Questions question 1