The BiosphereCHAPTER 21

A View of Earth from Space

• Biosphere: all the organisms on Earth, together with the physical environments in which they live

• Ecology: the scientific study of interactions between organisms and their biotic (living) and abiotic (nonliving) environment

Ecology: Understanding theInterconnected Web

• The organisms and physical environments of the biosphere can be thought of as forming a web of interconnected relationships

Ecology: Understanding theInterconnected Web

• Studying the interconnected relationships between organisms and their environments helps us understand our natural world and the impact we have on it

Climate• Climate: the prevailing weather conditions

experienced in a region over relatively long periods of time

• Organisms are more strongly influenced by climate than by any other feature of their environment. Why?

Incoming Solar Radiation Shapes Climate

• The angle at which the sun strikes Earth influences Earth’s different climates

• The increased solar energy at the equator promotes photosynthesis, resulting in more biomass

• Consumers depend on the productivity of producers

Water CurrentsAffect Climate

• Earth has four giant convection cells in which warm, moist air rises and cool, dry air sinks, generating relatively consistent wind patterns

• When cool, dry air from the polar regions collides with warm, moist air moving north, precipitation results in the temperate regions

Wind CurrentsAffect Climate

• Winds usually blow from a consistent direction in a given location and are called prevailing winds

Water Currents Affect Climate

• Ocean current formation is caused by:• The rotation of

Earth• Differences in

water temperature between the poles and the tropics

The Major Features of Earth’sSurface Also Shape Climate

• Large bodies of water absorb and release heat more slowly, creating a milder climate

• The climate of a place may also be affected by the presence of large lakes, the ocean, and mountain range.

What sites from the Cascades fieldtrip showed this?

The Major Features of Earth’sSurface Also Shape Climate

• Mountains often produce a rain shadow effect, in which little precipitation falls on the side of the mountain that faces away from the prevailing winds

This should look very similar to you. Why?

Biomes• Biomes can be categorized

based on the unique climatic and ecological features of each such region

• Terrestrial biomes • Land biomes• Classified by climate

• Aquatic biomes • Water biomes • Classified by physical and

chemical features (Ex. salt concentration)

Terrestrial Biomes

Which biome are we in?

The Location of Terrestrial BiomesIs Determined by Climate

• Climate is the most important factor controlling the location of natural terrestrial biomes– Especially

temperature and precipitation

The Location of Terrestrial BiomesIs Determined by Climate

• Climate is the most important factor controlling the location of natural terrestrial biomes– Especially

temperature and precipitation

Tundra

• Short Growing Season

• Covers nearly one-fourth of Earth’s land surface

• Frozen 10 months of the year

• Receives less precipitation than many deserts

• Permafrost: permanently frozen soil found below the surface layers of soil

• Trees are scarce • Dominated by: low-

growing flowering plants, such as grasses, sedges, moss, and lichens

Tundra Soil Peeled Back at Level of Permafrost - Alaska

Arctic Tundra-Alaska

Tundra

Boreal Forest• A few

coniferous species dominate

• Largest terrestrial biome

• Includes sub-Arctic landmass immediately south of the tundra

Boreal Forest

• Thin, nutrient-poor

• Rainfall is low in most boreal forests. – Where is an

exception?• Plant diversity is

relatively low and conifers dominate

Temperate Deciduous Forests

• Fertile soils. Why? • Relatively mild winters• By definition:– Winter lasts 4–5

months– Precipitation

distributed evenly through much of the year