37 exam-style questions on Climate and biomes — topic 2.4 of Ecology in the IB Environmental Systems and Societies syllabus — with answers and explanations. Samples below; the full set is free with an account.
Air over the equator is heated strongly, rises and cools. This rising limb of the Hadley cell is the main reason why equatorial regions have
Answer: low pressure and high annual rainfall
Rising air produces low pressure at the surface, and as it expands and cools the water vapour it carries condenses, giving heavy convectional rainfall. The same circulation cell delivers the opposite result at about 30 degrees, where the descending limb creates high pressure and deserts.
Tundra receives continuous daylight for several weeks in summer, yet its net primary productivity is among the lowest of all terrestrial biomes. The main reason is that
Answer: low temperatures and a short growing season limit photosynthesis
Light is only one input; in tundra the limiting factors are temperature and the length of the frost-free period, and waterlogged, frozen ground also slows the decomposition that would release nutrients. Tundra precipitation is in fact low, comparable with a cold desert.
Warming causes Arctic sea ice to melt, exposing open ocean water. The effect of this change on the climate system is best described as
Answer: a positive feedback, because the darker ocean absorbs more radiation
Albedo falls from roughly 0.6 for sea ice to about 0.06 for open ocean, so more shortwave radiation is absorbed, which drives further melting: the change reinforces itself and is therefore positive. Positive does not mean beneficial, and negative feedback would damp the change rather than amplify it.
Mean annual temperatures in a high-latitude region rise over several decades while annual precipitation stays much the same. The most likely change in biome distribution is that
Answer: boreal forest advances into land currently occupied by tundra
Biome boundaries track the envelope of temperature and precipitation that a vegetation type can tolerate, so warming lets trees establish beyond the present treeline and squeezes tundra towards the pole and coast. Soil development lags behind the climate shift but does not hold the boundary in place.
A beam of sunlight of a given width delivers more energy per square metre of ground at the equator than at 60 degrees north. The reason is that at the higher latitude the beam
Answer: strikes at a low angle and is spread over more surface
Latitude changes the angle of incidence, so the same beam is smeared across a larger area and the insolation per square metre falls; it also passes through more atmosphere on the way. That difference in energy input at the surface is the engine that drives the whole tricellular circulation.
Moist prevailing winds cross a mountain range. Annual rainfall on the leeward side is a fraction of that on the windward side. The reason is that air on the leeward side
Answer: descends, warms and its relative humidity falls
Descending air is compressed and warms, so it can hold more vapour than it carries and cloud evaporates instead of forming. This rain shadow is why deserts and dry grasslands so often lie immediately downwind of a mountain range.
That was 6 of 37 Climate and biomes questions.
Practise all 37 freeA student writes: 'Hot deserts lie near 30 degrees north and south because these latitudes receive the most intense solar radiation on Earth.'
See the correction →OutlineAO2 · 1–4 marks
A brief account or summary: the main points in two or three sentences, no evaluation.
DrawAO1 · 1–2 marks
A labelled, accurate drawing with a ruler where lines are straight; axes and units on a graph.
DescribeAO2 · 1–4 marks
Give a detailed account of what it is or how it happens — steps, features, pattern — without saying why.
37 Climate and biomes questions — free with an account. Spaced repetition, streaks and full exam simulations included.
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