c hapter 48 the biosphere. i mpacts, i ssues : s urfers, s eals, and the s ea el niño and the...
TRANSCRIPT
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