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    The Abiotic Earth

    The sun is the primary source of earth's energy.
    It drives and generates climate.

    Global variations in topography interact with wind, water,
    and other abiotic factors to create different types of soils.

    Global variations in climate and geology
    lead to diversity of biological systems.

    Climate and soils are the foundations of the biosphere.

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By NASA Earth Observatory

    Earth's Atmosphere

    The atmosphere is the layer of gases ("air")
    surrounding earth and retained by Earth's gravity.

    The atmosphere

    • retains heat
    • reduces temperature extremes
    • generates pressure needed for liquid water to form on earth
    • absorbs harmful short-wavelength solar and cosmic radiation

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(click on pic for source)

    Atmospheric Gases

    Air composition, temperature,
    and pressure vary with altitude,
    but its essential composition
    (by volume) is

    primary gases:
    • 78% nitrogen
    • 21% oxygen
    • 1% argon

    greenhouse gases:
    • 0.04% carbon dioxide
    • 0.4 - 1.0% water vapor
    • trace amounts of other gases
      (not all are greenhouse gases)

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    Atmospheric Regions

    The atmosphere can be divided into two main regions:
    • troposphere
      • from earth's surface to ~12km
    • stratosphere
      • from ~12km to 50-55km above earth's surface

    The tropopause is the interface
    between trophosphere and stratosphere
    .

    It is the altitude at which air ceases cooling with height,
    and is almost completely devoid of water vapor.

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    Solar Energy

    Solar Irradiance is
    • the flux of radiant solar energy per unit area
    • an instantaneous measurement of solar power per unit area
    • usually expressed as kilowatts/m2

    Insolation is

    • cumulative solar energy measured over per unit area
    • measured for a defined period of time (e.g., annual, monthly, daily)
    • usually expressed as kilowatt hours/m2
    • (a kilowatt hour = 1,000 watts/hour)

    Sunlight reaching Earth's surface ranges from
    ~250nm (ultraviolet) to ~1500nm (infrared).

    Solar irradiance is most intense when the sun is directly overhead
    in a cloudless sky, peaking near 540nm ("green").

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    The Greenhouse Effect

    Not to be confused with global warming, the Greenhouse Effect
    is a natural phenomenon that allows life on earth to exist.

    Greenhouse gases:

    • H2O vapor
    • CO2

    • CH4
    • N2O
    • O3
    • hydrofluorocarbons (anthropogenic)
    Greenhouse gas molecules absorb and reflect solar energy
    • arriving from the sun
    • being reflected from Earth's surface

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(source: NASA)

    Small Change, Big Effect

    The warming effect is similar to that of the glass panes in a greenhouse.
    • higher concentration of greenhouse gases --> higher temperatures
    • lower concentration of greenhouse gases --> lower temperatures

    Oxygen and nitrogen, the two most abundant atmospheric gases,
    are not greenhouse gases.

    Because greenhouse gases comprise such a small fraction
    of the atmosphere
    (required link!), a small change
    in their concentration can have significant effect.

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(click for larger image)


(click for larger image)

    Is it me, or is it getting warm in here?

    If you were born after 1977, you have not experienced
    a colder-than-average year.

    February 1985 was the last month with below average temperatures.

    In the 20th century...

    • The average global temperature anomaly was zero. HOWEVER...
    • Most colder-than-average years occurred in the first 50 years.
    • Most warmer-than-average years occurred in the last 50 years.

    February 2019 was the 34th consecutive February
    with temperatures above the 20th century average.

    December 2018 marked more than 400 consecutive months
    of temperatures above the 20th century average.

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    Sunlight Quality and Quantity

    Terrestrial sunlight's
    • spectral distribution (quality)
    • irradiance (quantity)

    depend on
    • insolation angle of incidence
    • environmental conditions

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    Sunlight Varies with Latitude

    Because of Earth's curvature, insolation varies with latitude.

    Latitudes away from the equator receive oblique insolation,
    which spreads sunlight over a larger area.

    Thus, northern and southern latitudes receive
    less energy per unit area than equatorial latitudes.

    The difference varies over the course of the year.

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(click on pic for source)

    Unequal Solar Heating
    Creates Climate Zones

  • The polar regions lie above 60oN and S
  • The temperate regions lie between
    • 30oN and 60oN in the Northern Hemisphere
    • 30oS and 60oS in the Southern Hemisphere.
  • The subtropics lie between
    • Tropic of Cancer (23.5oN) and 30oN
    • Tropic of Capricorn (23.5oS) and 30oS
  • The tropics lie between the
    • Tropic of Cancer (23.5oN)
    • Tropic of Capricorn (23.5oS)

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(click on pic for larger image)

By USDA-ARS and Oregon State University (OSU)

    Agricultural Growth Zones

    The tropics
    • receive the highest annual input of solar energy
    • are the only place on earth where the sun
      ever shines directly overhead
    • This occurs on the equinoxes
      • March 21
      • September 21

    <-- Topography creates smaller climatic regions
    xxx within the global zones.

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    Albedo

    Terrestrial surfaces do not all reflect solar energy to the same degree.

    Albedo is the percentage of solar radiation striking a surface that is reflected back by that surface

    Light colored surfaces have higher albedo than dark colored surfaces.
    Surface textures and humidity can affect albedo.

    Albedo magnifies the effects of unequal insolation on a global level.

    • equator: low albedo of ocean and forests
    • poles: high albedo of ice

    Albedo also can have strong effects at a local level.

    • Low albedo of concrete and asphalt increase heat.
    • Unlike on soil or vegetated areas, surface water evaporates rapidly.
    • Unlike on soil or vegetated areas, surface water cannot be absorbed.
    • This contributes to lower atmospheric humidity over concrete/asphalt.
    • Regions with large areas of concrete/asphalt receive lower rainfall.

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(click on pic for larger image)

    Equinoxes and Solstices

    The earth is tilted 23.5o on its axis, defining the tropics.

    Because of this tilt, insolation varies over the course of the year
    in each hemisphere.

    Flora and fauna are profoundly affected by these changes.

    • equinoxes - day and night are the same length
    • solstices - days when the sun reaches its highest
      xxxxxxxxxxor lowest point at noon (depending on hemisphere)

    The Tilt of Earth's Axis is the Reason for the Seasons.

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(click on pic for source)

    Perihelion and Aphelion

    The earth is not always equidistant from the sun

    • Perihelion
      • ~ January 3 - earth is closest to the sun
      • ~ 147,500,000 km between earth and sun
    • Aphelion
      • ~ July 4 - earth is farthest from the sun
      • ~ 152,500,000 km between earth and sun

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    Days of Greatest Irradiance

    The sun is directly overhead only the solstices and equinoxes
    at high noon, and only at specific latitudes.

  • on the Summer Solstice (~ June 21)
  • at the Tropic of Cancer (23.5o N)

  • on the Winter Solstice (~ Dec 21)
  • at the Tropic of Capricorn (23.5o S)

  • on the Vernal Equinox (~ March 20)
  • at the equator

  • on the Autumnal Equinox (~ Sept 22)
  • at the equator

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    Four Properties of Air Generate Air Currents

    Unequal solar warming generates atmospheric convection currents.

    Four properties of air influence the generation of these currents:

    • density
      • Warm air expands, and is less dense than cool air
      • Warm air rises; cool air descends

    • water vapor saturation point
      • As air temperature increases, it's capacity to hold water vapor increases.
      • When it reaches saturation point, water condenses and falls.
      • Cool air has a lower saturation point.
      • When warm wet air cools, you get precipitation.

    • latent heat release
      • Liquid water --> water vapor requires high energy input.
      • Water vapor --> liquid water releases the stored energy as heat.
      • At saturation point, air is warmed by this conversion.

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    Adiabatic Cooling and Heating

    Near earth's surface, gravity concentrates atmospheric molecules.
    At higher altitudes, molecules are less dense.
    Thus, lower altitudes have higher pressure than higher altitudes.

  • When air molecules move from earth's surface to higher altitude
    • they expand (pressure decreases)
    • they undergo fewer collisions
    • This process results in cooler air temperatures,
      and is known as adiabatic cooling.

  • When air molecules move from higher altitude to earth's surface
    • then condense (pressure increases)
    • they undergo more collisions
    • This process results in warmer air temperatures,
      and is known as adiabatic heating.

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    Atmospheric Circulation Cells

    Adiabatic heating and cooling around the earth's surface
    results in the generation of air circulation cells.

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    Atmospheric Circulation Cells

    At the equator
    • intense sun heats air at the earth's surface.
    • Hot air rises and and undergoes adiabatic cooling.
    • As air cools, its capacity to hold water vapor decreases.
    • Water precipitates as rain near the equator.
    • As rain precipitates, latent heat energy is released.
    • Air continues to warm and rise.

    At the tropopause

    • cold, dry air moves horizontally away from the equator

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    Hadley Cells

    At 30oN and 30oS
    • Hadley Cells form between the equator and 30o (N and S).
    • cool air falls back to earth.
    • Falling air undergoes adiabatic heating.
    • By the time it reaches earth's surface, it is hot and dry.
    • Most of the world's deserts are located at 30oN and 30oS
    • The region where the two Hadley Cells meet
      is known as the intertropical convergence zone (ITCZ).

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(click on pic for source)

    The Doldrums

    The doldrums (equatorial calms)
  • The ITCZ extends about 5o to the north and south of the equator.
  • Here, northern and southern trades collide, neutralizing each other.
  • Intense insolation causes air to rise with little lateral movement.
  • There is often very little wind in the ITCZ.
  • Sailing ships can be stuck there for weeks.
  • The region is named for the personal sluggishness
    known as "the doldrums".

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    Polar Cells

    At 90oN and 90oS (poles), cold, dry air falls.
    • Polar Cells form between 90o and 60o(N and S).
    • A polar vortex (~1000km in diameter) forms at each pole.
    • The vortex can consist of one or two cells.
    • Because this air is dry, very little precipitation falls at the poles.
    • Land masses at the poles are frozen deserts.

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    Ferrell Cells

    Between 60oand 30o(N and S) air circulates between the two other cells.
    • Ferrell cells form between the Hadley and polar cells.
    • Ferrell cell air movement is driven by that in the adjoining two cells.
    • Ferrel cell is like a "gear" between the Hadley and polar cells.
    • At 60o N and S, warmed, moist air rises and condenses.
    • High rainfall and cool temperatures at 60oN allow
      temperate rainforests to flourish in some areas.

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    Cells and the ITCZ Move Seasonally

    Because of earth's tilt, the solar equator moves
    between 0o and 23.5o N and S over the course of the year.
    The ITCZ shifts along with the cells.

    Seasonal movement of the ITCZ causes
    seasonal changes in rainfall patterns.

    Rainy season occurs when the ITCZ is on or close to a particular region.

    The regions encompassed by the Ferrell cells
    have less distinct convection currents
    than the Hadley and Polar cells.

    In these areas, wind direction can change dramatically.
    This results in greater variation in temperature and precipitation.

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    Coriolis Effect Generates Wind Currents

    Because the earth is spherical, speed of rotation varies with latitude.
    • equator - 1670km/hr
    • 30o N or S - 1445 km/hr
    • 80o N or S - 291 km/hr

    Because of this, anything not firmly attached to the earth itself
    (air, water) is deflected to the east or west it moves north or south.

    Surface winds are deflected, causing the Coriolis Effect.

    • to the right in the northern hemisphere
    • to the left in the southern hemisphere

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    Coriolis Effect: Prevailing Winds

    The Coriolis Effect is responsible for
    • semi-permanent high and low pressure regions
    • generation of prevailing winds

    • Northeast trade winds (northern Hadley cell)
      • blow from east to west
    • Southeast trade winds (southern Hadley cell)
      • blow from east to west
    • Westerlies
      • occur in northern and southern Ferrell Cells
      • more variable than trade winds
      • generally blow from west to east
    • Polar Easterlies
      • dry, cold prevailing winds at northern and southern poles
      • polar high pressure forces air towards the equator
      • Coriolis deflects winds from east to west.

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    Hurricane Spin

    Coriolis Effect also explains why hurricanes rotate
    • counterclockwise in the northern hemisphere
    • clockwise in the southern hemisphere

    (But the thing about water spiraling down the drains?
    That's a myth.)

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    Jet streams

    The physical processes that produce global air cells
    also produce jet streams.

    The temperature gradient between polar air and warmer air
    from lower latitudes draws air towars the poles.

    Jet streams are relatively shallow, narrow
    fast-moving air currents at various levels in the atmosphere.

    Four global jetstreams formed just below the tropopause
    have major impacts on global climate and weather.

    • polar jet streams
    • subtropical jet streams

    Coriolis, geography and shifting temperatures
    create a complex, constantly changing pattern of wind currents.

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(modified from original art by Fred the Oyster)

    Rossby Waves

    Rossby waves form in the polar jet stream when

    • polar air moves toward the Equator while
    • tropical air moves toward the poles

    These waves generate

    • low pressure cells (cyclones)
    • high pressure cells (anticyclones)
    ...within the Ferrel cells.

    Cyclones and anticyclones are important generators of weather
    in the Ferrell cell latitudes.

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(modified from original art by Fred the Oyster)

    Rossby Waves and the Polar Vortex

    Unusual heat waves and flooding have been occurring
    in Eurasia with increasing frequency.

    Major, crippling, winter cold spells have hit
    the northern U.S. with increasing frequency.

    Rather than "disproving global warming",
    these spells are a direct result of anthropogenic climate change.

    The explanation lies in the destabilization of the polar vortex
    and the resulting increase in Rossby wave amplitude
    .

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(modified from original art by Fred the Oyster)

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(click on pic for source)

    Ocean Currents

    Ocean currents move
    • warm water from the equator towards the poles
    • cold water from the poles towards the equator

    The Coriolis Effect generates a gyre in each major ocean

    • clockwise in the northern hemisphere
    • counterclockwise in the southern hemisphere

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    Surface and Deep Currents

    Currents are generated and affected by
    • tides (gravitational pull of moon and sun on earth)
    • wind
    • thermohaline circulation
    • ocean floor topography
    • Coriolis Effect

    • Surface currents
      • comprise the upper 10% of water mass
      • are generated primarily by wind and tides
    • Deep currents
      • comprise the lower 90% of water mass
      • are generated primarily by thermohaline circulation

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(click on pic for source)

    The Great Ocean Conveyor Belt

    This deep current is generated primarily by thermohaline circulation.
      1. Warm Gulf Stream water flows to the Norwegian Sea.
      2. Freezing increases water salinity.
      3. Cold, salty water is more dense, and sinks.
      4. Warm Gulf Stream water moves in to take its place.
      5. Warm water cools, sinks, and the cycle continues.

      6. Cold water on the bottom flows south, past the equator,
      xx Antarctica.

      7. Wind-driven upwelling brings cold water to the surface.
      8. A "conveyor belt" is generated, encircling the globe.

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By NOAA (click on pic for larger image)

    The Conveyor Belt is Slowing Down

    The conveyor belt is slow (a few cm/sec).
    A drop of water staying in the belt
    would take about 1000 years to complete the circuit.

    Ocean warming due to anthropogenic climate change
    is causing the conveyor belt to slow down even more.

    Possible effects of this change are uncertain.

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By NOAA (click on pic for source)

    Upwelling

    Strong winds blowing from continents
    can push surface ocean water out to sea.

    Deep, cold water from below rises up to replace it,
    a phenomenon known as upwelling

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By NOAA

Downside: upwelling can push planktonic larvae
out to open ocean, away from their productive "nursery" coastal habitat.

    Upwelling: Nutrients and Biodiversity

    Water and sediments at the bottom of the ocean
    are rich in nutrients.

    Upwelling brings these nutrients to the surface.

    The result is an increase in

    • algae, plant, and phytoplankton biomass
    • marine consumer biomass
    • terrestrial (coastal) consumer biomass
    • biodiversity

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By NOAA

    Global Upwelling Regions

    Coastal upwelling regions
    • occupy about 1% of the ocean surface
    • provide ~50% of world's fisheries catch

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    ENSO: El Niño, La Niña

    Perhaps the most famous upwellings
    is the El Niño-Southern Oscillation (ENSO),
    and its counterpart, La Niña which normally
    occur every 10-12 years.

    These events can affect weather patterns
    thousands of miles away.

    El Niño conditions usually commence in late December
    ("El Niño" = Christ Child), and may last for several months.

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(click on pic for source)

    El Niño vs. La Niña

    El Niño
    • reduced trade winds
    • reduced upwelling
    • increased precipitation outside the tropics
    • drought in So America, SE Asia, Australia
    • loss of nutrients disrupts food chains

    La Niña
    • increased trade winds
    • increased upwelling
    • return to "normal"

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(click on pic for source)

    A Fragile Ecosystem

    Small, fragile ecosystems are most strongly affected by El Niño,
    perhaps none moreso than The Galapagos Islands.

    Under normal conditions, the Cromwell Countercurrent
    on the west side of the archipelago brings up cold, nutrient-rich water.

    Phytoplankton blooms, providing plentiful food for animals.

    The Cromwell Countercurrent upwelling has allowed
    this ecosystem to become a hotspot of evolution and biodiversity.

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Galapagos penguin in 2016, during El Niño (left)
Galapagos penguin in 2017, post-El Niño (right)
(click on pic for source)

    El Niño is Hard on the Galapagos

    But in an El Niño cycle...
    • upwelling is reduced
    • precipitation increases
    • increased terrestrial plant growth, production
    • marine nutrients diminish
    • phytoplankton and algae die
    • Die-offs move up the food chain

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By Citynoise

    Land and Water Hemispheres

    Large-scale, global factors can affect local climate.

    The Northern and Southern Hemispheres are very different
    in terms of water vs. landmass surface coverage.

    This creates very different climates in the two hemispheres.

    1. Continental land mass vs. water mass.
    Ocean and lakes cover

    • 81% of southern hemisphere
    • 61% of northern hemisphere

    2. Proximity to the ocean

      Inland areas and coastal areas differ significantly in
      overall annual temperature, humidity, and wind patterns.

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By Citynoise

    Local Geographic Features

    Other, smaller scale features also can affect local climate.

    1. Coastal mountain ranges
    • ocean wind blowing inland meets mountain
    • as air rises, it cools and precipitates.
    • dry air crosses to the leeward side
    • rain shadow is a dry area on the leeward side of a coastal range

    2. Topography
    • steep slopes drain well --> xeric conditions
      • desert
      • chaparral
      • dry forest
    • level areas tend to retain water --> wet conditions
      • mesophyte forests
      • floodplains
      • riparian ecosystems

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Abiotic Factors and Organic Evolution

A region's climate determines the composition and diversity of its flora (plant life).
Climate and flora directly affect composition and diversity of the fauna (animal life).

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    Temperature

    • contributes to erosion and creation of soil
    • affects evolution of temperature tolerance in living organisms
    • has direct effects on biological macromolecules

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Hydrophytes:

Mesophytes:

Xerophytes:

    Water

  • contributes to soil erosion and creation.
  • is a vital component of organism habitats.
  • Natural selection can be driven by
    • lack of water in terrestrial environments
    • lack of solutes in fresh water

    Animals that have secondarily returned to marine environments
    face different osmotic challenges because the ocean is saltier
    than when their ancestors left it.

    Green plants have evolved water-related adaptations:

    • Hydrophytes are adapted for a very wet environment.
    • Mesophytes are adapted for a moderately wet environment.
    • Xerophytes are adapted for a very dry environment.

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    Sunlight

    Living organims are profoundly affected by sunlight
    • intensity
    • daily duration
    • angle of incidence (seasonal changes)

    Natural selection is driven by competition for light
    in many terrestrial plant communities.

    Aquatic community composition varies with depth,
    in response to natural selection resulting in
    different species having different light requirements and tolerances.

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(click on pic for larger image)

    Photoperiodicity Evolves in Response to Light

    Photoperiodicity is the pattern of biological phenomena
    driven by the regularly recurring (daily and seasonal)
    changes in light and dark.

    Photoperiodicity can cycle

    • on a 24-hour cycle (Circadian rhythm)
    • monthly
    • annually

    ...depending on the biological activity
    (mating, sleep cycle, hibernation, etc.).

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    Wind

    • contributes to erosion

    • affects desiccation rate in animals, plants, fungi

    • affects plant growth form
      • The photos on the left both show .
      • The top photo shows Pinus jeffreyi in a relatively windless habitat.
      • The bottom photo shows the same species in a very windy habitat.

    • affects animal and plant body temperature via
      • evaporation & evaporative cooling
      • convection

    Different forms of the same species generated by differences in
    environmental factors are called ecotypes of that species.

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(click on pick for SOIL HORIZONS)

    Rocks and Soil

    • Topography creates habitat
    • The pH and mineral content of rock affect
      flora composition and diversity.
    • Composition of aquatic soil substrate
      affects water quality (dissolved minerals, pH).

    Soil deposits can be

    • eluvium - soil/sediments derived in situ by
      weathering and/or gravity
      x(adjective = eluvial)
    • alluvium - soil/sediments deposited by running water
      x(adjective = alluvial)

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    Major Environmental Disturbances

    Natural disasters such as
    • fire
    • severe storms (hurricanes, tornadoes, etc.)
    • volcanic activity
    • insert your favorite environmental catastrophe here

    ...can have major effects on ecosystems.

    Such events can affect flora and fauna composition
    and diversity in many ways, even causing extinctions.

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