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AP Environmental Science
• Different climates lead to different communities of organisms,
especially vegetation.
• Biomes – large terrestrial (land) regions characterized by similar
climate, soil, plants, and animals.
• Each biome contains many ecosystems whose communities have adapted
to differences in climate, soil, and other environmental factors.
• Weather: physical conditions of the lower atmosphere that occur over
hours or days.
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Temperature
Precipitation
Humidity
Cloud coverage
Etc.
• Climate: long term differences in temperature and precipitation
• 3 decades (30 years) to 1000s of years
• This distinction is important when discussing climate change/global
warming. Long term data should be used. Climate matters because it
determines where humans and other species can survive.
• Tropical – areas near the
equator, receives the most
intense sunlight
• Polar – areas near the poles,
receives the least intense
sunlight
• Temperate - between
tropical and poles
• Climate varies in different
parts of Earth because of an
uneven distribution of heat
and precipitation around the
world by air and ocean
currents.
1. Uneven heating of the
Earth’s surface by the sun
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Air is heated more at the
equator where the sun
strikes directly, strikes the
poles at an angle and
covers a larger area.
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Tropical = hot
Polar = cold
Temperate = hot and cold
seasons
More solar radiation =
more evaporation = more
condensation = more
precipitation
2. Rotation of Earth on its
axis.
• Spins faster at the equator
than the poles
• Hot air collects, rises and
moves north & south to cooler
areas
• Cells- huge areas
distinguished by direction of
air movement
• Prevailing Winds – different
directions of air movement
• Blow continuously, distribute
heat & moisture around Earth,
drive ocean currents
3. Properties of air, water,
& land
• Sun evaporates water 
transfer of heat from
oceans to atmosphere 
creation of convection cells
 vertical circulation of
air, heat, moisture
• Mass movement of surface water in the oceans
• Created by heat from the sun and changes in water density
• Warm currents are shallow and less salty
• Cold currents are deeper and salty
• Driven by
prevailing winds
and Earth’s rotation
• Interrupted by
continents
• Air circulation patterns,
prevailing winds, the
configuration of continents,
and ocean currents form 6
giant cells (3 above/3
below the equator)
• These lead to the uneven
distribution of heat &
moisture, resulting in
varying climates, and
biomes
• Deserts, grasslands, forests,
etc.
1. Climate near Large Bodies of Water
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Water absorbs /releases heat slower than land
Oceans/Lakes moderate weather & climate of nearby land by
absorbing solar radiation
2. Climates of Cities
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Bricks, concrete, asphalt absorb & hold heat
Building block wind flow
Vehicles & heating/cooling systems release large amounts of heat &
pollutants
All these cause more haze/smog  increase temperatures  decrease
in wind speeds
3. Climate near Mountains
• Mountains interrupt the flow of prevailing winds/storms forcing them
upwards
• Upward = cooling  moisture condenses/falls on the windward slope
• Dry air passes over mountain and flows down the leeward slope & warms
• Rain shadow effect  formation of deserts (Death Valley)
• Greenhouse gases: water, carbon dioxide, nitrous oxides,
methane present in the lower atmosphere.
• Natural Greenhouse effect: natural warming effect of the
troposphere.
• Allows life to be sustained on Earth
• Human acts are increasing the amount of greenhouse gases in
the atmosphere by:
• Burning fossil fuels
• Clearing forests (deforestation)
• Growing crops/raising cattle
• Front: a boundary between two air masses with different
temperatures and densities.
• Warm Front
• Warm air advances on cool air  warm air is less dense at slide atop the
cool air forms condensation (clouds)  clouds thicken & descend 
precipitation
• Causes cloudy skies and drizzle
• Cold Front
• Cold air advances on warm air  cold air is more dense and wedges
below the warm air  produces tall thunderbolt clouds
• Causes high winds and thunderstorms but leaves clear skies and cooler
temps
• Jet streams: rapidly flowing air current (strong winds) that
move east to west in a wavy pattern.
• Located at the top of the troposphere
• Strong influence on weather patterns
• Atmospheric Pressure- caused by the collision of high speed
molecules in the air
• Mostly oxygen & nitrogen
• Greater at the Earth’s surface because they are squeezed under the air
above them
• High – air mass with high pressure
• Cool dense air that slowly descends becoming warmer
• Causes clear skies and fair weather
• Low – air mass with low pressure
• Warm air with low density rises and cools  condensation  clouds form
 precipitation
• Causes cloudy, stormy weather
• Dew point – temperature at which condensation takes place
• Condensation nuclei – particles of dust, smoke, sea salts, or
volcanic ash that serve as surfaces for rain to form on
• Upwelling – upward movement of ocean water, mixes the
upper levels and lower levels of sea water
• Upper levels – warm, phytoplankton
• Lower levels – nutrient rich
• El Nino – Southern
Oscillation (ENSO) – the
weakening or reversal of the
tropical trade winds that
normally blow east to west
(Pacific Ocean)
• Causes drought in Australia, S.
East Asia & storms in W. United
States
• Can be tracked
• La Nina – reverse of ENSO,
normal conditions
• More Atlantic hurricanes, colder
winter in Canada and NE United
States, rains SE Asia
• Tornadoes – over land
• Form when large, dry
cold front runs into a
mass of warm, humid air
• Tropical Cyclones –
over ocean
• Hurricanes (Atlantic),
Typhoons (Pacific)
• Form when low pressure
cells grow over warm
tropical waters
• The most important factors in a biome are temperature and
precipitation.
• Biomes tend to converge around latitude lines on the globe.
• The evaporation is greater than the precipitation (usually less
than 25 cm/year).
• Covers 30% of the earth.
• Variations in annual
temperature (red) and
precipitation (blue) in
tropical, temperate and
cold deserts.
• The rainfall is erratic & fires are common. It has & shrubs that
are good for grazing animals.
• Variations in annual
temperature (red) and
precipitation (blue) in
tropical, temperate and
cold deserts.
• The tropical &
subtropical grassland.
• It is warm all year long
with alternating wet &
dry seasons.
• Temperate Grasslands
• These are coastal areas.
Winters are mild & wet,
w/ summers being long,
hot, & dry.
• Chaparral has a
moderate climate but its
dense thickets of spiny
shrubs are subject to
periodic fires
• Temperate Grassland
• The cold winters and hot
dry summers have deep
and fertile soil that make
them ideal for growing
crops and grazing cattle.
• Polar Grassland
• Covers 10% of earth’s
land. Most of the year,
these treeless plains are
bitterly cold with ice &
snow. It has a 6 to 8
week summer w/ sunlight
nearly 24 hours a day.
• covered with ice and
snow except during a
brief summer.
• Forests have enough
precipitation to support
stands of trees and are
found in tropical,
temperate, and polar
regions.
• Just south of the tundra
(northern part of N.
America), it covers 11%
of earth’s land. Its
winters are long, dry &
cold. Some places have
sunlight 6 to 8 hours a
day. The summers are
short and mild, w/
sunlight 19 hours a day.
• High-elevation islands of
biodiversity
• Often have snowcovered peaks that
reflect solar radiation
and gradually release
water to lower-elevation
streams and ecosystems.
• Consist mostly of conebearing evergreen trees
that keep their needles
year-round to help the
trees survive long and
cold winters
• Near the equator. It has
warm temperatures, high
humidity & heavy rainfall.
• Tropical rain forests have
heavy rainfall and a rich
diversity of species.
• Found near the equator.
• Have year-round uniformity
warm temperatures and
high humidity
• Coastal areas support
huge cone-bearing
evergreen trees such as
redwoods and Douglas
fir in a cool moist
environment
• It has moderate
temperatures, long, warm
summers, cold winters &lots
of rain. Trees include oaks,
hickory, maple, and beech.
• Most of the trees survive
winter by dropping their
leaves, which decay and
produce a nutrient-rich soil.
• Forests = ~ 30% of Earth’s land surface
• Types of Forests:
• Old-growth/Primary Forests: uncut or regenerated forest that has not
been seriously disturbed
• Very diverse
• Second-growth Forests: resulting from secondary ecological succession
• Tree plantation/tree farm/commercial forest: managed forests
containing one or two species of trees, all the same age
• Less diversity
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Ecological Services
Support energy flow and
chemical cycling
Reduce soil erosion
Absorb/release water
Purify water/air
Influence climate
Store atmospheric carbon
Provide wildlife habitats
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Economic Services
Fuel wood
Lumber
Pulp for paper
Mining
Livestock grazing
Recreation
Jobs
• Clearing for agriculture, livestock grazing, timber, and
urban development
• Conversion of diverse forests to tree plantations
• Damage from off-road vehicles
• Pollution of forest streams
• Forest fires
• Insects
• Climate change
• Selective Cutting: older trees cut singularly or in small groups
• Clear-Cutting: removing all trees from an area
• Advantages: higher timber yields, maximum profits, reforest with fast
growing trees, good for trees needing full/moderate sunlight
• Disadvantages: reduces biodiversity, destroys/fragments habitats,
increases water pollution, flooding, erosion, eliminates recreational value.
• Surface fires: burn undergrowth and leaf litter on forest floor
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Kills seedlings, small trees, mature trees and most animals escape
Helps prevent more serious fires
Free up valuable nutrients
Release seeds from cones
Control disease & insects
• Crown fire: extremely hot fire that goes from treetop to treetop,
burning whole trees
• Destroy most vegetation/wildlife, increase soil erosion, burn human structures
• Not major long term threat, promotes secondary succession
• Serious short term threats- habitat loss, increased CO2 & other
pollutants
• Temporary for permanent removal of large areas of forest
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Decreased soil fertility from erosion
Runoff leads to more soil in aquatic ecosystems
Premature extinction of specialized species
Loss of habitat
Regional climate change
Increase of CO2 in atmosphere
Acceleration of flooding
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Roads
Fires
Settler Farming
Cash crops
Cattle ranching
Logging
Tree plantation
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Identify & protect areas with higher biodiversity
Rely more on selective cutting and strip cutting
No clear cutting on steep slopes
No logging old-growth forests
Leave dead trees/fallen timber for nutrient recycling
New tree plantations only on already deforested/degraded
land
• Certify timber
• Forest fire management
• Prescribed burns, awareness
• Most widely used & altered by human activities after forests
• Ecological Services
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Soil formation
Erosion control
Chemical cycling
Storage of CO2
Biodiversity
• Rangelands: unfenced
grasslands in temperate
& tropical climates that
supply forage for
grazing (grass-eating)
and browsing (shrubeating) animals.
• Cattle, sheep, goats graze
42% of grasslands
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• Pastures: managed
grasslands or fenced
meadows planted with
domesticated
grass/crops
• Overgrazing: when too many animals graze for too long,
damaging grass & their roots
• Exceeds carrying capacity of the land area
• Leads to soil erosion, soil compacting (drying out of soil), invasive species
that animals will not eat
• Sagebrush, cactus, mesquite
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Conversion to cropland
CO2 release from burning grasslands
Oil production/off-road vehicles
Urbanization
• Rotational grazing: cattle are confined to an area for a short
time to graze (1-2 days), then moved to another section of
land.
• Providing supplemental cattle feed, supply water tanks/ponds,
& salt licks
• Suppressing the growth of invader plants by use of herbicides,
mechanical removal, controlled burning
• More expensive, used less
• Allowing short term trampling in areas of invader plants by
animals
• Replanting severely degraded areas with native grass/seeds
• expensive
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Large desert cities
Off-road vehicles
Soil salinization from irrigation
Depletion of ground water
Land disturbance & pollution from mineral extraction
• Because deserts are ecosystems with slow plant growth, low
diversity, slow chemical cycling, and little water, it takes them a
very long time to recover from degredation.
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Agriculture
Timber/mineral extraction
Dams
Air pollution
Off-road vehicles
Glacial melthing
• Map the world’s terrestrial ecosystems and create an inventory
of the species in each & the services they provide
• Locate and protect the most endangered species, especially
plant biodiversity
• Restore degraded ecosystems
• Make it worth it to people to protect biodiversity
• Tax breaks, technical help, etc.
• Restoration: returning an area
back to its natural state (as close
to)
• Rehabilitation: returning an area
back into a function ecosystem, but
not its natural state
• Replanting trees, removing pollutants
• Replacement: replacing an
ecosystem with another type of
ecosystem
• Degraded forest becomes tree
plantation or pasture
• Creating artificial ecosystems:
artificial wetlands to reduce
flooding, etc.
• How?
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Identify causes
Eliminate or sharply reduce the causes
Reintroduce key species
Protect the area from further
degradation & allow secondary
succession to occur