Chapter Notes: Arctic Tundra Biome

Arctic Tundra Biome

• Location and Definition: North Pole and northern regions (Canada, Alaska, Greenland, Iceland, Europe, Russia); characterized by similar climates and organisms.

• Formation: Youngest biome, formed ~10,000 years ago post-ice age.

• Coverage: Covers 20% of Earth’s surface; barren landscape with poor soil and no trees.

Climate and Seasons

• Seasons: Two predominant seasons.

• Winter: Lasts up to 10 months; temperatures can reach -56 °C, with snow cover.

• Permafrost: Underground layer frozen all year; can be up to 600 meters deep.

The Active Layer

• Description: Thin layer of thawed soil (~30 cm) during summer; below it lies the permafrost.

• Summer Conditions: Temperatures can rise to 24 °C with continuous sunlight; significant melting of snow.

• Soil Characteristics: Active layer becomes waterlogged due to poor drainage; surface ponds form as runoff feeds into streams and the Arctic Ocean.

• Growing Season: Brief 10-week period for plants and animals to thrive and reproduce before winter.

Caribou are well-suited for life in the Arctic due to several adaptations:

• Physical Adaptations:
  
    - Thick Fur: Provides insulation against extreme cold temperatures, including a soft underlayer that traps air for warmth.
  
    - Body Size: Generally larger bodies minimize heat loss relative to their surface area (Bergmann’s rule).
  
    - Hoof Structure: Broad, concave hooves provide stability and support on snow and uneven terrain, helping them travel in harsh conditions.

• Behavioral Adaptations:
  
    - Migration: Caribou undertake long migrations to find food, which helps them cope with seasonal changes when food availability varies.
  
    - Social Behavior: They often travel in herds, which provides protection from predators and warmth through group huddling.

These traits have evolved over thousands of years through natural selection, adapting to their cold environments for survival and reproductive success.