Major Biomes: Ecosystems of the World

A biome is a large, relatively distinct terrestrial region with similar climate, soil, plants, and animals, regardless of where it occurs in the world.

A treeless biome in the far north with harsh, cold winters and extremely short summers.
Precipitation: 10-25 cm/yr.
Warmer temperature: short growing season of 50-160 days.
Frost can occur even in summer.
Plant diversity is low.
Low primary productivity.
Nutrient-poor soils with little organic material.
Permafrost present.

Forest biome that occurs in temperate areas with a moderate amount of precipitation.
Precipitation: 75-150 cm/yr.
Temperature: seasonality, hot summers, and cold winters.
Topsoil is rich in organic matter and clay-rich lower layer.
Vegetation is primarily deciduous.
Animals: deer, bear, and other small animals.

Grasslands with hot summers, cold winters, and too little precipitation to support trees.
Precipitation: 25-75 cm/yr.
Includes tall grass prairies and short grass prairies.
90% of this biome has been lost to farmland.
Soil has a thick organic matter rich organic horizon.
Periodic fires keep the dominant vegetation.
Animals: once covered with bison, smaller animals are still present.

Biome composed of thickets of drought-adapted evergreen shrubs and small trees, and grasses.
Mediterranean climate: mild, moist winters, and hot dry summers.
Soil is thin and often not fertile.
Vegetation: dense growth of evergreen shrubs with small sclerophyllous leaves.
Periodic fires are a major factor in plant succession.
Animals: mule deer, chipmunks, many species of birds.

Lush, species-rich biome that occurs where climate is warm and moist throughout the year.
Precipitation: 200-450 cm/yr.
Very productive biome.
Most species-rich biome.
Occurs in areas with ancient, highly weathered, nutrient-poor soil.
Nutrients are tied up in vegetation, not soil.
Forest has three distinct canopy layers.
Animals: most abundant insect, reptiles, and amphibians on earth.

Represent 2% of Earth's surface.
Rivers and Streams: features of a typical river.
Marshes and Swamps: land that is shallow, fresh water covers for at least part of the year.
Water-logged soil.
Water-tolerant vegetation.
Estuaries: a coastal body of water, partly surrounded by land, with access to the open ocean and a large supply of freshwater from a river.
Highly variable environment.
Highly productive.

The variety of living species on Earth, including plants, animals, bacteria, and fungi.
Kinds of Diversity: genetic, species, and ecological.
Benefits of Diversity:
- Ecological stability.
- Helps biological communities withstand environmental stress and recover from disturbances.
- Economic benefits for humans.
- Provides food and medicines.
- Provides cultural, ecological, educational, historical, recreational, aesthetic, and scientific value.
Biodiversity Hotspot: areas with high species richness and high threat levels.

Extinction: mass extinction through history.
Habitat destruction and fragmentation: example, Cadiz Township in Wisconsin.
Global climate change.
Over exploitation: market hunting, medicinal and pet trades, cyanide fishing-tropical fish.
Pollution: example, Bald eagles and other bird species were decimated by DDT in the 1960s.
Introduced/Invasive species.
Disease.

Hunting and fishing laws.
Endangered Species Act (1973).
Habitat Conservation Plan (HCP) is a required part of an application for an Incidental Take Permit.