ESS 2.4 - Climates and Biomes

distinguish the difference between weather and climate

weather - atmospheric conditions over a short period

climate - average atmospheric conditions over a long period

define biomes

a group of comparable ecosystems that have developed in similar climatic conditions, wherever they occur

list the six main factors that govern the distribution of biomes

• insolation - the amount of solar radiation received by an area

  • influenced by axis tilt

• precipitation - amount and distribution of rainfall/snowfall in an area

• temperature - average and seasonal variation in temperature

• latitude + altitude

• rain shadow - a region with significantly lower precipitation on the leeward side of a mountain due to the obstruction of moist air by the mountain range

• differential heating - the variation in temperature due to differing surface properties and angles of sunlight

draw the tricellular model and explain its function

how Earth's atmosphere circulates air in three distinct cells per hemisphere—the Hadley, Ferrel, and Polar cells—driven by uneven solar heating between the equator and poles

identify the characteristics of each cell within the model

Cell	Latitude Range	Air Movement Pattern	Surface Winds	Climate Impact
Hadley	0° to ~30°	Warm air rises at equator, sinks at 30°	Trade winds (easterly)	Tropical rain near equator; deserts at 30°
Ferrel	~30° to ~60°	Air moves poleward at surface, rises at 60°	Westerlies	Mid-latitude stormy, variable weather
Polar	~60° to 90°	Cold air sinks at poles, rises at 60°	Polar easterlies	Cold, dry polar climate

list the 5 categories of biomes

aquatic (freshwater/marine)

forest

grassland

desert

tundra

describe the 3 characteristics for aquatic biomes

limiting factors

• water absorbs light = limits photosynthesis

• deep oceans = no light for photosynthesis

• freshwater = freeze in temperate + polar winters

biodiversity

• coral reefs = very high

• temperate freshwater = moderate to low

• deep oceans = low

productivity

• tropical coral reefs = high

• temperate freshwater = mid

• deep oceans = very low

describe the 3 characteristics for forest biomes

limiting factor

• nutrients locked in biomass instead of soil (TRF)

• high rainfall = leach nutrients (TRF)

• thin soil (TRF)

• temperate forests = cold dry winters

biodiversity

• very high

• TRF = highest on earth

• temperate = 2nd highest

productivity

• TRF = very high

• temperate = high productivity lower in autumn/winter

describe the 3 characteristics for grassland biomes

limiting factors

• less precipitation than forest, higher than desert

• seasonal temperature extremes

• low decomposition + nutrient cycling

biodiversity

• high

• diverse plant life

• rich nutrient soils

• supports extensive food webs

productivity

• moderate - low

• slow nutrient cycles + season temperatures

describe the 3 characteristics for desert biomes

limiting factors

• little precipitation

• high evaporation

• extreme day/night temp differences

• photosynthesis limited = low water

biodiversity

• low

• extremes of precipitation + temp = low plant + animal survival

productivity

• low

• water needed for photosynthesis

• good nutrient soils bcs minimal leaching

describe the 3 characteristics for tundra biomes

limited factors

• short days = limited photosynthesis + productivity

• frozen water in winter + post-thaw soil = limited photosynthesis

• slow nutrient cycles

biodiversity

• limited

• too cold for cold blooded species

productivity

• low

• same as limiting factors

identify the reasons behind biome shift

biomes are moving because of

1. increase in mean global temperature

2. changes in precipitation

3. climate change

list ways the climate is changing

• temp increase of 1.5-4.5 Celsius by 2100

• higher latitudes = greater warming

• more warming in winter

• drier or warmer areas

• stronger storms

• organisms lack adaptability = have to migrate

provide an example of a biome shift

The Sahara Desert has expanded by about 10% during the 20th century, largely due to a combination of natural climate variability and human-driven climate change. This expansion is linked to the widening of the Hadley cell, which causes dry, sinking air to extend further poleward, creating more desert conditions in subtropical regions. The desert's southern boundary has moved into the Sahel, a semi-arid zone, reducing rainfall and causing drying of water bodies like Lake Chad, which signals broader regional drying. About one-third of this expansion is attributed directly to climate change, while natural cycles explain the rest. This biome shift threatens ecosystems and agriculture in affected countries, illustrating how Hadley cell changes drive desertification.