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Lecture Outline
Does a Cactus Grow in Brooklyn?
A. Unrelated species in distant regions often show striking similarities.
B. The distribution of species is related to climate, topography, and species
interactions.
C. Biosphere Defined
1. Biosphere = earth regions where organisms live.
2. Hydrosphere = all water on or near the earth’s surface.
3. Lithosphere = the earth's outer, rocky layer.
4. Atmosphere = gases, particles, and water vapor enveloping the earth.
D. Global Patterns of Climate
1. Climate includes temperature, humidity, wind velocity, cloud cover, and rainfall.
2. Climate is shaped by four factors:
a. variations in the amount of incoming radiation,
b. the earth’s daily rotation and annual revolution,
c. the world distribution of continents and oceans,
d. the elevation of land masses.
49.1
Air Circulation Patterns and Regional Climates
A. The atmosphere exerts mediating effects.
1. Ultraviolet radiation is absorbed by ozone and oxygen in the upper atmosphere.
2. Clouds, dust, and water vapor in the atmosphere absorb and reflect solar
radiation.
3. Radiation warms the earth’s surface and generates heat that drives the earth’s
weather systems.
B. The sun differentially heats equatorial and polar regions creating the world's major
temperature zones.
1. Warm equatorial air rises, cools, releases its moisture, and spreads northward
and southward where it descends at 30o latitudes as very dry air (results in
deserts).
2. The air is warmed again and ascends at 60o latitudes; as it moves toward the
poles, regional areas receive varying amounts of rainfall that in turn influence
ecosystems.
C. Seasonal variations in climate result from the earth's revolution around the sun.
1. The amount of solar radiation reaching the earth’s surface changes in the
Northern and Southern hemispheres; this results in seasonal changes in climate.
2. In temperate regions, organisms respond most to changes in daylength and
temperature; in deserts and tropical regions, they respond more to seasonal
changes in rainfall.
49.2
The Ocean, Land Forms, and Regional Climates
A. Ocean Currents and Their Effects
1. Ocean water covers about three-fourths of the earth's surface.
2. Latitudinal and seasonal variations in solar heating cause ocean water to warm
and cool on a vast scale.
a. Surface waters tend to move from the equator to the poles, warming the air
above.
b. Currents form because of the earth’s rotation, winds, variations in
temperature, and distribution of land masses.
c. Immense circular water movements in the Atlantic and Pacific Oceans
influence the distribution of ecosystems.
B. Regarding Rain Shadows and Monsoons
1. Topography refers to physical features of a region, such as elevation.
2. Mountains, valleys, and other features influence regional climates.
a. Monsoon rains occur when warm winds pick up ocean moisture and release
it over the cooler land masses of Asia and Africa.
b. The mountains of the western United States cause the winds from the ocean
to rise, cool, and lose their moisture.
c. As the winds descend on the leeward (eastern) slopes, they gain moisture
from the earth and its vegetation causing a rain shadow effect.
49.3
Realms of Biodiversity
A. Biogeography is the study of the global distribution of species, each of which is
adapted to regional conditions.
1. By convergent evolution, species living in the same place undergo natural
selection resulting in modified organisms that resemble one another very closely.
2. Biogeographic realms are broad land regions with characteristic types of plants and
animals; there are six of these.
a. Climatic factors determine patterns of vegetation and explain why unrelated
species may have similar adaptations.
b. Barriers isolate species and restrict dispersal.
B. A biogeographical realm may be divided into biomes:
1. Biomes are broad vegetational subdivisions including all animals and other
organisms.
a. Biome distribution corresponds with climate, topography, and soil type.
b. The form of the dominant plants tells us something of the weather
conditions.
2. Ecoregions are portions of biomes which have identified as possessing species
vulnerable to extinction.
49.4
Soils of Major Biomes
A. Soil is a mixture of rock, mineral ions, and organic matter.
1. The size of the rock can range from gravel, to sand, silt, and clay.
2. The organic matter, in variable stages of decomposition, is called humus.
B. Soil profiles are define the composition of soil from the surface downward.
1. Topsoil has the most humus and is the most vulnerable to weathering.
2. Loam topsoils have the best mix of sand, silt, and clay for agriculture.
49.5
Deserts
A. Deserts are areas where evaporation exceeds rainfall.
1. Most deserts lie between 30o north and south latitudes.
2. Vegetation is scarce but there is some diversity; day/night temperatures fluctuate
widely.
B. More than a third of the world’s total land area is arid or semiarid due to drought
and overgrazing, which can lead to desertification.
49.6
Dry Shrublands, Dry Woodlands, and Grasslands
A. Dry shrublands and dry woodlands prevail in western and southern coastal regions
between the latitudes of 30° and 40°.
1. The climates is semiarid; rains occur during mild winter months; summers are
long, hot, and dry; dominant plants have tough, evergreen leaves.
2. Dry shrublands prevail when rainfall is less than 25–60 cm (example: the highly
flammable California chaparral).
3. Dry woodlands occur when rainfall is about 40–100 cm; there are trees but not in
dense forests.
B. Grasslands sweep across much of the interior of continents, in the zones between
deserts and temperate forests.
1. Characteristics include: flat or rolling land, high rates of evaporation, limited
rainfall, grazing and burrowing animals, and few forests.
2. There are three basic types in North America:
a. Shortgrass prairie of the American Midwest is typified by short, droughtresistant grasses that have been replaced by grains that require irrigation.
b. Tallgrass prairie was originally found in the American West where water was
more plentiful.
C Savannas such as the African savanna are hot, dry and bear small bushes among the
grass.
D. The monsoon grasslands of southern Asia experience seasons of torrential rain
alternating with near drought.
49.7
Tropical Rain Forests and Other Broadleaf Forests
A. Evergreen broadleaf forests lie across the tropical zones of the world.
1. These occur between 20° N and S latitude.
2. Most typical is the tropical rain forest where high temperatures, rainfall, and
humidity promote luxuriant plant growth, competing vines, and incredible
animal diversity.
B. Deciduous broadleaf forests lie farther from the equator; the regions are more mild
in temperature with moderate rainfall
1. In the tropical deciduous forest, many trees drop some or all of their leaves during
the pronounced dry season.
2. The monsoon forests of Southeast Asia also have such trees.
3. In the temperate deciduous forests of North America, conditions of temperature and
rainfall do not favor rapid decomposition; thus, nutrients are conserved to
provide fertile soil.
49.8
Coniferous Forests
A. The typical “tree” in these forests is some variety of evergreen cone-bearer with
needlelike leaves.
B. These forests are found in widely divergent geographic areas:
1. Boreal forests (or taiga) are found in the cool to cold northern regions of North
America, Europe, and Asia; spruce and balsam fir are dominant.
2. Montane coniferous forests extend southward through the great mountain ranges;
fir and pine dominate.
3. Temperate rain forest parallels the west coast of North America and features
sequoias and redwoods.
4. Southern pine forests grow in the sandy soil of several Atlantic and Gulf coast
states.
49.9
Arctic and Alpine Tundra
A. Arctic tundra lies to the north of the boreal forests; it is a vast treeless plain, very
cold, with low moisture; it is characterized by permafrost, which prevents growth of
large trees.
B. Alpine tundra occurs at high elevations in mountains throughout the world.
49.10
Freshwater Provinces
A. Lake Ecosystems
1. A lake is a body of standing freshwater produced by geologic processes, as when
an advancing glacier carves a basin in the Earth.
a. The littoral zone extends from the shore to where rooted plants stop growing.
b. The limnetic zone includes open, sunlit waters beyond the littoral to a depth
where photosynthesis is no longer significant; plankton life is abundant.
c. The profundal zone is the deep, open water below the depth of light
penetration; detritus sinks from the limnetic and is acted upon by
decomposers.
2. Seasonal Changes in Lakes
a. In temperate regions, lakes undergo changes in density and temperature.
b. In winter, ice (less dense) forms on the surface over water that is warmer,
much of it at 4o C (greatest density), and heavier.
c. During the spring overturn, warming and winds cause oxygen to be carried
downward and nutrients to the surface.
d. By midsummer a thermocline between the upper warmer layers and lower
cooler layers prevents vertical warming.
e. During autumn, the upper layers cool and sink causing a fall overturn.
3. Trophic Nature of Lakes
a. Glaciers carve out basins, which become filled with water to form lakes.
b. Interactions of soils, basin shape, and climate produce a continuum of
trophic structure.
c. Oligotrophic lakes are deep, nutrient-poor, and low in primary productivity.
d. Eutrophic lakes are shallow and nutrient-rich often due to agricultural and
urban runoff wastes.
B. Stream Ecosystems
1. Three kinds of habitats form along a continuum from head waters to river’s end.
a. Riffles are shallow, turbulent stretches where water flows swiftly over sand
and rock.
b. In pools, deep water flows slowly over a smooth, sandy or muddy bottom.
c. Runs are fast-flowing waters with a smooth surface and a bottom of bedrock
or rock and sand.
2. Various factors have an impact on streams:
a. Average flow and temperature are influenced by geography, altitude, and
forest shade.
b. Volume and temperature vary with rainfall, snow melt, drought, and the
seasons.
c. Chemistry and pollution of the water depend on materials leached into, or
added to, the stream.
d. Streams erode their valleys and participate in cycles of erosion and
redeposition of sediments and nutrients.
49.11
The Ocean Provinces
A. The open ocean covers about three-fourths of the Earth's surface.
1. The benthic province includes all the sediments and rocky formations of the ocean
bottom; its zones begin with the continental shelf and extend downward to the
deep-sea trenches.
2. The pelagic province includes the entire volume of ocean water and is subdivided
into two zones:
a. The neritic zone constitutes the relatively shallow water overlying the
continental shelves.
b. The oceanic zone is the water over the ocean basins; photosynthetic activity is
restricted to the surface.
B. Primary Productivity in the Ocean
1. Photosynthesis proceeds on a vast scale and varies seasonally.
2. As much as 70 percent of the ocean's primary productivity may be due to
ultraplankton, tiny photosynthetic bacterial cells.
C. Hydrothermal Vents
1. Here very cold water at the ocean bottom seeps into fissures, is heated, then
spewed forth mixed with minerals.
2. Bacteria provide the starting point for complex communities of tube worms,
crustaceans, clams, and fishes.
49.12
Wetlands and the Intertidal Zone
A. Mangrove Wetlands and Estuaries
1. "Mangrove" refers to forests in sheltered regions along tropical coasts.
a. Ocean waves cannot reach these regions so anaerobic sediments and mud
accumulate.
b. Salt-tolerant plants with shallow, spreading roots abound here.
c. The net primary productivity of mangrove wetlands depends on the volume
and flow rate of the water moving in and out with the tides.
2. Estuaries are partially enclosed regions where fresh and salt water meet.
a. Estuaries are incredibly productive feeding and breeding grounds for many
animals.
b. Many estuaries are declining because of upstream diversion of the
freshwater that is necessary for their maintenance.
B. Rocky and Sandy Coastlines
1. The inhabitants of the intertidal-zone are alternately exposed and submerged;
existence is difficult.
2. Rocky shores have three vertically arranged zones:
a. The upper littoral is submerged only during the highest possible lunar tide; it
is sparsely populated.
b. The mid-littoral is submerged during the regular tide and exposed at the
lowest tide of the day.
c. The lower littoral is exposed only during the lowest lunar tide.
3. Sandy and muddy shores are rather unstable stretches of loose sediments;
detrital food webs occur; invertebrates are plentiful.
49.13
El Nino and the Biosphere
A. Upwelling Along the Coasts
1. Upwelling is the upward movement of deep, nutrient-rich water along the
margins of continents.
a. Under the influence of northern winds and the earth's rotation, water along
the western coasts of the Northern Hemisphere move westward where cold,
deep water moves in vertically to replace it.
b. At places where currents stir the ocean water and circulate nutrients,
primary productivity increases.
B. Oscillating Currents and Weather Patterns
1. Every three to seven years, the warm surface waters of the western equatorial
Pacific move eastward to the coasts of South and Central America to cause
"downwelling"—a phenomenon known as El Niño.
2. The currents affect the weather patterns over land.