Overview
This lecture covers terrestrial (land-based) biomes, focusing on their global distribution, environmental conditions, and the adaptations of organisms found within them. It also explores how climate and nutrient availability shape biomes and discusses the impact of climate change on biome distribution.
Characteristics and Definition of Biomes
- Biomes are geographic areas defined by average yearly temperature and precipitation (climate).
- The main defining characteristics of biomes are their temperature and precipitation ranges.
- Climate is the combination of average temperature and precipitation trends over a year.
Major Biomes and Their Distribution
- Tropical rainforests have high annual rainfall and warm temperatures.
- Deserts are defined by very low precipitation and often high temperatures.
- Tundra and boreal forests are cold, dry biomes found farther from the equator (~60° latitude).
- Temperate biomes, like grasslands and seasonal forests, are found at mid-latitudes (30°–60°) with moderate rainfall and temperatures.
- Tropical biomes, including rainforests and savannas, occur near the equator with high temperatures and precipitation.
Adaptations of Organisms
- Organisms are uniquely adapted to their biome's climate.
- Camels store fat in their humps and cacti have waxy coatings to survive deserts.
- Plants like shrubs and wildflowers have deep roots to store energy and regrow after disturbances like wildfires.
Nutrient Availability in Biomes
- Soil nutrient levels affect which plants and animals can survive in each biome.
- Tundra has low nutrients due to frozen soils that limit decomposition and water availability.
- Tropical rainforests have nutrient-poor soils because intense plant growth quickly absorbs nutrients.
- Boreal forests also have nutrient-poor soils due to slow decomposition caused by cold temperatures.
- Temperate forests have nutrient-rich soils due to leaf litter and moderate temperatures promoting decomposition.
Changes in Biome Distribution
- The distribution of biomes is shifting due to climate change.
- As global temperatures rise, biomes like the boreal forest are moving northward.
- Areas previously too cold for certain species are becoming habitable, while southern regions may become too warm.
Key Terms & Definitions
- Biome — A large geographic region characterized by specific climate conditions and communities of organisms.
- Climate — The average yearly pattern of temperature and precipitation in an area.
- Adaptation — A trait that helps an organism survive in its environment.
- Nutrient Availability — The amount of soil nutrients accessible for plant growth.
- Permafrost — Permanently frozen soil found in the tundra.
Action Items / Next Steps
- Identify one characteristic of a biome and explain how it determines the community of organisms found there.