Chapter 50 Ecology and the Biosphere
Key Vocabulary Terms: ecology, biosphere, biotic, abiotic, organism, population, community, ecosystem,
global winds, doldrums, prevailing westerlies, trade winds, convection cell, rain shadow, windward vs. leeward,
turnover, stratification, photic zone, aphotic zone, thermocline, benthic zone, detritus, littoral zone, limnetic
zone, profundal zone, eutrophic vs. oligotrophic lakes, wetland, estuary, intertidal zone, neritic zone, pelagic
zone, coral reefs, terrestrial biome, tropical rainforest, savanna, desert, temperate deciduous forest, temperate
grassland or prairie, tiaga, tundra, permafrost
Chapter Outline
THE GENERAL CIRCULATION OF THE ATMOSPHERE
Distribution of Biomes Are a Result of the Earth`s Features
Presence of mountains or valleys
Soil type
Amount of heat reaching surface
Global atmospheric circulation
The Sun and Atmospheric Circulation
Heat energy transferred in various forms
Receives short-wave radiation from sun
Radiates long-wave radiation back into space
Ultraviolet radiation absorbed by oxygen and ozone
Climate depends on amount of energy received from sun`s rays
Perpendicular at equator, more intense over given area
Greater angle at poles, energy spread over greater area
Variation results from spherical shape of earth
Earth`s rotation on axis and annual orbit affect climate
Inclination of axis tilted 23.5%
Orbit and angle of inclination produce seasons
Major Atmospheric Circulation Patterns
Equatorial north/south pattern of air flow
Warm air at equator rises and flows to poles
Called doldrums
Draws air from north and south latitudes
Air cools as it rises, thus loses moisture to tropics
Air sinks at 30% latitude, is reheated at surface
Results in zone of lesser precipitation
Warm air continues northward to poles
Rises at 60% latitude and flows to equator
Results in zone of very low precipitation near poles
Earth`s rotation causes an east/west air flow
Trade winds at 30% latitude
From east-southeast to west in southern hemisphere
From east-northeast to west in northern hemisphere
Prevailing westerlies at 30 to 60% latitude
Blow from west to east
Dominate climate patterns
Weak zones of east to west winds at extreme latitudes
Atmospheric Circulation, Precipitation, and Climate
Precipitation related to air temperature
Warm air holds more moisture than cool air
Greater rainfall when air rising and being cooled
Lesser rainfall when air falling and being warmed
All great deserts at near 60% latitude
Other major deserts at continental interiors
Other deserts on leeward side of mountain ranges
Rain shadow effect: drier on windward side of mountain
Areas with climate resembling the Mediterranean
Small, isolated and widely separated areas
California, southwestern Oregon
Central Chile
Southwestern Australia
Cape region of South Africa
Prevailing westerlies blow from cool ocean to warm land
Air holds moisture, thus precipitation limited during summer
Monsoon conditions of India and southern Asia
Winter trade winds blow east-northeast onto ocean
Summer winds blow east-southeast onto land
Results in heavy rains in certain regions
Patterns of Circulation in the Ocean
Oceanic air circulation modified by land masses
Surface gyrals dominate ocean circulation
Clockwise in north, counterclockwise in south
Redistribute heat and affect continental climates
Gulf Stream carries warmth to England and western Europe
Humboldt Current carries cold water up the west U.S. coast
FRESH WATER
Limited in Area, About 2% of Earth`s Surface
Strongly connected to terrestrial habitats
Marshes and swamps constitute intermediate zones
Supplied with nutrients from nearby land communities
Freshwater organisms generally restricted to that habitat
Ponds and Lakes Subdivided into Three Zones
Littoral zone: shallow waters along edge of land
Limnetic zone: top layer of open water
Profundal zone: deep-water areas with no light penetration
Large Lakes Exhibit Thermal Stratification
Summer conditions
Upper epilimnion layer
Lower, cooler hypolimnion layer
Layer of temperature change called thermocline
Fall conditions
Epilimnion temperature drops; layers mix
Called fall overturn
Winter conditions
Water most dense at 4% C, thus cooler surface water freezes
Water below ice remains between 0% and 4%
Spring conditions
Water warms and mixes with cool water below
Called spring overturn
Lakes Divided into Two Productivity Categories
Eutrophic lakes
Abundant minerals, organic matter
In summer oxygen is depleted below the thermocline
Overturns redistribute nutrients and oxygen
Oligotrophic lake
Organic matter and nutrients relatively scarce
Frequently very deep
Deep water always rich in oxygen
More drastically affected by pollution and algal blooms
THE OCEANS
Dominate Earth`s Surface Composition
Three quarters of surface covered by water
Average depth of three kilometers
Photosynthetic organisms limited to upper surface
Water density affects mineral and gas solubility
Warm water holds less oxygen than cold
Carbon dioxide not limited in oceans
Mineral distribution more uniform than on land
Fewer number of species in ocean than on land
Greater variety of niches on land
All phyla represented in oceans, but few species of each
Few phyla represented on land, but many species of each
Three Major Kinds of Oceanic Habitats
Neritic zone: shallow waters along coasts
Surface zone: top layer of open ocean
Abyssal zone: deep-water areas of ocean
The Neritic Zone
Inhabited by comparatively large number of species
Intense, violent interactions between land and sea
Intertidal (littoral) region exposed when tide recedes
Inhabitants generally well-secured
Provided transition from ocean to land habitats
Organisms adapted to resist desiccation
Abundant nutrients from land support great continental shelf fisheries
Heavily populated areas, like Chesapeake Bay, damaged
Coral reefs occur in tropical waters
Highly-productive ecosystems in nutrient-poor waters
Productivity related to photosynthetic organisms
The Surface Zone
Composed of microscopic plankton and macroscopic nekton
Photosynthetic plankton accounts for 40% of all photosynthesis on earth
Heterotrophic organisms abundant
Largest animals (whales) feed directly on plankton
Great fluctuations in populations of plankton
Results in rapid turnover of nutrients
Productivity of region may be grossly underestimated
The Abyssal Zone
Area of sea floor twice that of exposed land masses
Sea floor covered by thick layer of fine mud
Initially expected to contain little life
High pressures, low temperature
Absence of light and lack of food sources
Recent discovery of wide array of life
Free-swimming frequently bioluminescent animals
Clusters of organisms around deep-sea thermal vents
Depend on chemosynthesis rather than photosynthesis
Superheated water rich in reduced compounds
Bacteria contained in animal tissue provides food
BIOMES
Biomes Are Terrestrial Communities Occurring Over Wide Areas
Classified by General Features of Vegetation
Climatically Delineated
If earth`s surface were uniform(nomountains or oceans), bands would be formed
Changes in altitude mimic changes in latitude
Tropical Rain Forests
Substantial rainfall throughout year
Richest biome in terms of number of species
Great diversity of life forms in well-lighted upper regions
Epiphytes in tree branches
Vines characteristic of tropical forests
Hemiepiphytes begin as epiphytes, later grow roots into soil
Life forms highly specialized and unusual
Composition of soils
Frequently acidic
Deficient in phosphorus, potassium and other nutrients
May contain toxic levels of aluminum
Most nutrients concentrated in trees and other life forms
Fragile regions readily damaged by human populations
Cleared land does not sustain continued agriculture
Increased populations cannot be supported
Cleared forests take decades to recover
Destruction accompanied by loss of vast diversity of life
Organisms of great scientific interest
Potentially important to the quality of human life
Desert
Extremely low rainfall
Concentrated within continents and at 20 to 30% latitudes
Greatly fluctuating daily temperatures
Extreme heat during day
Rapidly radiate heat at night, may drop 30 °C
Sparse vegetation, primarily annual plants
May pass dry season in form of seeds
Germinate and grow rapidly after rainfall
Trees and shrubs exhibit deep root systems
May be deciduous or evergreen
Convergent evolution: unrelated organisms appear
superficially similar
Succulents common, exhibit CAM photosynthesis
Animal life may limit activity to specific seasons
Possess unique adaptations
Live in moist, deep burrows and emerge at night
Exhibit water-resistant cuticles and exoskeletons
May estivate to avoid hot, dry conditions
Savannas
Reduced rainfall with prolonged dry seasons
Open grassland with scattered shrubs and trees
Trees generally deciduous and lose leaves in dry season
Constitution maintained by periodic fires
Nutrient-poor soils are especially high in aluminum
Wider fluctuations in temperature than rain forests
Characteristic large grazing mammals
Widespread in North America during Pleistocene Epoch
Temperate Grasslands
Common in interior of Eurasia, South America,and pre-colonial
North America
Highly productive when converted to agriculture due to rich soil
Grasslands with long, cold winters
Variety of plant forms dependent on rainfall
Tall-grass prairies with moderate rainfall
Forests with abundant rainfall
Short-grass prairies with lower rainfall
Sensitive to overuse
Mismanagement results in desert formation
Populated by herds of grazing mammals
Maintained by grazing and periodic fires
Temperate Deciduous Forests
Exemplified by forests of Eastern U.S., Canada, Eurasia
Life forms changing with climatic conditions
World climate becoming cooler, drier and more seasonal
Eastern North America resembles western China
Moderate rainfall
Distributed throughout seasons
Moisture not available during cold winters
Many areas possess rapidly growing perennial herbs
Taiga
Northern coniferous forests of Eurasia and North America
Long, cold dry winters with most precipitation in summers
Deep blanket of snow in winter
Protects ground from freezing, allows for growth of forest
Changes in day length as a result of latitude
Short days in winter
Long days in summer
Rapid plant growth in summer months
Willows, birches common around lakes and marshes
Alders with nitrogen-fixing bacteria inhabit infertile
glacial soils
Variety of animal life
Large mammals: elk, moose, wolves
Small mammals: rodents
Tundra
Farthest north, excluding regions of permanent ice
Extremely uniform appearance
Types of vegetation
Small trees around open water
Mostly grasses, sedges, heathers and lichens
Grow rapidly in summer months
Very low precipitation
Water sits on frozen ground in summer
Permanent ice, permafrost near surface
Various animal life, especially during short summers