IB Environmental systems and societies 2.4B Biomes Notes

Biomes: Global Ecosystems Shaped by Temperature and Rainfall

1. Biomes are global-scale communities defined by a distinctive climate, vegetation structure, and adapted organisms.
2. Each biome is a unique combination of temperature, precipitation, and insolation, which shapes its biodiversity and productivity.
3. Ecosystems within the same biome often evolve parallel structures because they face similar environmental pressures.

What Determines Where Each Biome Forms

1. Insolation
   1. The amount of sunlight drives temperature and photosynthesis.
   2. Equatorial regions receive high insolation and support lush vegetation; polar regions receive little and support only tundra.
2. Temperature
   1. Low temperatures give cold biomes such as tundra and boreal forest (Siberia, Canada).
   2. High temperatures give warm biomes such as deserts and rainforests.
3. Precipitation
   1. High rainfall (over 2,000 mm/year) supports dense rainforest.
   2. Low rainfall (under 250 mm/year) gives desert.
   3. Seasonal rainfall produces grassland and savanna.

Parallel Features Across Similar Biomes

1. Similar climates in different parts of the world produce analogous ecosystems through convergent evolution.

Reading Biomes from a Climate Graph

1. For any given temperature and rainfall, one natural biome tends to develop.
2. This is shown on a climograph (or Whittaker diagram): mean annual temperature on the horizontal axis, mean annual precipitation on the vertical axis, with each biome occupying a distinct zone.

The Major Terrestrial Biomes

1. Biomes are grouped by their shared abiotic conditions.
2. Each one differs in its limiting factors, productivity, and biodiversity.

Tropical Rainforests