CHAPTER 48

The Biosphere

IMPACTS, ISSUES: SURFERS, SEALS, AND THE SEA El Niño and the winter of 1997-1998

was an excellent season for surfers and disastrous for seals and sea lions

Displaced currents along the Pacific coast failed to churn up nutrients important to primary producers and marine food webs

Effects moved through the food web to fishes and squid, the main food of seals and sea lions

BIOGEOGRAPHY

The study of the distribution of

organisms and the processes that

underlie distribution patterns

FACTORS THAT AFFECT DISTRIBUTION

Geologic history

Topography

Climate

Species interactions

BIOSPHERE

Sum total of the places in which organisms

live

Includes portions of the hydrosphere,

lithosphere, and atmosphere

CLIMATE

Average weather condition in a region

Affected by: amount of incoming solar radiation

prevailing winds

elevation

THE ATMOSPHERE

Three layers

Outer mesosphere

Middle stratosphere (includes ozone layer)

Inner troposphere (where air is warmed by

the greenhouse effect)

OZONE LAYER

Region 17 to 27 kilometers above sea level in

the stratosphere

Molecules of ozone absorb most layers of

ultraviolet light

Protects living organisms from excess exposure

to UV light

THERMAL INVERSION

Weather pattern in which a layer of cool, dense air is trapped beneath a layer of warm air

cool air

warm inversion air

cool air

Figure 48-7 Page 870

ACID DEPOSITION

Affects much of eastern North America

Caused by the release of sulfur and nitrogen

oxides

Coal-burning power plants and motor vehicles

are major sources

BIOMES

Regions of land characterized by habitat conditions and community structure

Distinctive biomes prevail at certain latitudes and elevations

HOT SPOTS Portions of biomes that show the greatest

biodiversity

Conservationists are working to inventory and protect these regions

24 hot spots hold more than half of all terrestrial species

SOIL CHARACTERISTICS

Amount of humus

pH

Degree of aeration

Ability to hold or drain water

Mineral content

DESERTS

Less than 10 centimeters annual

rainfall, high level of evaporation

Tend to occur at 30 degrees north and

south and in rain shadows

One-third of land surface is arid or

semiarid

Fig. 48-14a, p.877

DRY SHRUBLANDS AND WOODLANDS

Semiarid regions with cooler, wet winters and hot, dry summers

Tend to occur in western or southern coastal regions between latitudes of 30 and 40 degrees

Fig. 48-16, p.878

EFFECTS OF DEFORESTATION

Increased leaching and soil erosion

Increased flooding and sedimentation of downstream rivers

Regional precipitation declines

Possible amplification of the greenhouse effect

TROPICAL RAIN FORESTS

Have the greatest variety of insects,

most bird species

Some tropical forest species may prove

valuable to humans

Forests are in areas with fast-growing

human populations

ARCTIC TUNDRA

Occurs at high

latitudes

Permafrost lies

beneath surface

Nutrient cycling

is very slow

 Arctic tundra in Russia in summer

Fig. 48-21b, p.883

LAKES

Bodies of standing freshwater

Eutrophic: shallow, nutrient-rich, has

high primary productivity

Oligotrophic: deep, nutrient-poor, has

low primary productivity

LITTORALLIMNETIC

LITTORAL

PROFUNDAL Figure 48.28Page 886

Lake Zonation

THERMAL LAYERING

In temperate-zone lakes, water can form distinct layers during summer

THERMOCLINE

Figure 48-28Page 886

SEASONAL OVERTURN

In spring and fall, temperatures in the lake

become more uniform

Oxygen-rich surface waters mix with deeper

oxygen-poor layers

Nutrients that accumulated at bottom are

brought to the surface

EUTROPHICATION

Enrichment of a body of water with nutrients

Can occur naturally over long time span

Can be triggered by pollutants

Fig. 48-29, p.887

ESTUARY

Partially enclosed area where saltwater

and freshwater mix

Dominated by salt-tolerant plants

Examples are Chesapeake Bay, San

Francisco Bay, salt marshes of New

England

ESTUARINE FOOD WEBS

Primary producers are phytoplankton and salt-

tolerant plants

Much primary production enters detrital food

webs

Detritus feeds bacteria, nematodes, snails,

crabs, fish

PHYTOPLANKTON

Floating or weakly swimming photoautotrophs;

form the base for most oceanic food webs

Ultraplankton are photosynthetic bacteria

PRIMARY PRODUCTIVITY

Primary producers are usually the phytoplankton

Productivity can vary seasonally

north temperatenorth polar

tropical

HYDROTHERMAL VENTS

Openings in ocean floor that spew mineral-rich, superheated water

Primary producers are chemoautotrophic bacteria; use sulfides as energy source

Tube worms at hydrothermal vent

Figure 48-38 Page 893

UPWELLING

Upward movement of water along a coast; replaces surface waters that move away from shore

Figure 48-37Page 892