Overview
This lecture covers the global distribution, defining characteristics, and adaptations of terrestrial biomes, as well as how climate change can shift biome locations.
Defining Terrestrial Biomes
- Biomes are regions defined by average yearly temperature and precipitation (climate).
- Major biomes include rainforests, deserts, tundra, boreal forest, temperate forest, and savanna.
- Temperature and precipitation are the main factors that determine biome type and location.
- Biomes follow predictable patterns across Earth, largely based on distance from the equator.
Adaptations in Biomes
- Organisms in each biome have unique adaptations to survive in their specific climate.
- Example: Camels store fat in humps and cacti have waxy coats to survive desert dryness.
- Example: Shrubs with deep roots can regrow after wildfires due to stored energy.
Global Distribution Patterns
- Tundra and boreal forest are cold, dry biomes found far from the equator (≈60° latitude).
- Temperate biomes (e.g., temperate grassland, temperate forest) are found in middle latitudes (30–60°).
- Tropical biomes (rainforest, savanna) are near the equator and have warm temperatures and high rainfall.
Nutrient Availability in Biomes
- Soil nutrient availability affects which plant species can survive in a biome.
- Tundra soils are nutrient-poor due to permanent freezing and limited decomposition.
- Tropical rainforest soils are nutrient-poor because nutrients are rapidly absorbed by dense vegetation.
- Boreal forest soils lack nutrients as cold temperatures slow decomposition.
- Temperate forests have nutrient-rich soils from leaf litter and moderate decomposition rates.
Biome Shifts Due to Climate Change
- Climate change can cause the geographic range of biomes (e.g., boreal forest) to move northward as formerly frozen soils thaw.
- Regions that become too warm may lose characteristic biome species.
Key Terms & Definitions
- Biome — A large region characterized by specific temperature and precipitation patterns and distinct plant and animal communities.
- Climate — The long-term average of temperature and precipitation in an area.
- Adaptation — A trait that helps an organism survive in its environment.
- Permafrost — Permanently frozen soil found in tundra regions.
Action Items / Next Steps
- Identify one characteristic of a biome and explain how it determines the community of organisms found there (concept explanation practice).