Chapter 5 Outline: Ecosystems and the Physical Environment
Intro:
 Organisms interact with the abiotic environment to produce and maintain
the chemical composition of the atmosphere
 Dynamic equilibrium: the steady state that earth’s environment and
organisms are in (rate of change is in the opposite direction)
 Feedback occurs when a change in one part of the earth’s system leads to a
change in another part
o Negative feedback mechanism- a change in some condition triggers
a response that counteracts, or reverses, the changed condition
(works to keep a system in dynamic equilibrium
o Positive feedback mechanism- a change in some condition triggers
a response that intensifies the changing condition (leads to greater
change from the original condition)
 Gaia Theory: the hypotheses that Earth’s organisms adjust the environment
to keep it habitable for life
o First proposed by a British chemist named James Lovelock and a U.S
biologist named Lynn Margulis in the 1970s
o Geophysiology- the field of study based on the Gaia Theory
 Biochemical cycles: process by which matter cycles from the living world to
the nonliving physical environment and back again
o Five different cycles: (important because these make up the
chemical compounds in cells)
 Carbon-form gaseous compounds
 Nitrogen-form gaseous compounds
 Phosphorus- does not form gaseous compounds
 Sulfur-form gaseous compounds
 Hydrologic-readily evaporates
The Carbon Cycle
 Carbon
o Makes up approx. 0.038% of the atmosphere as a gas, cardon
dioxide
o Present in the ocean in several forms: dissolved carbon
dioxide(carbonate and bicarbonate)
o Carbon cycle: the movement of carbon between organisms
and the abiotic environment (includes the atmosphere, ocean,
and sedimentary rock)
 Photosynthesis: plants, algae, and certain bacteria remove their
carbon dioxide from the and fix it into chemical compounds then
those compounds are used for cellular respiration where it returns
the carbon dioxide to the atmosphere
 Fossil Fuels: combustible deposits in earth’s crust, composed by the
remains of ancient organisms
 Combustion: when organic molecules are rapidly oxidized

Carbon Silicate Cycle: the worldwide circulation of carbon from the
abiotic environment into organisms then back into the abiotic
environment
o Step1: the weathering process- atmospheric carbon dioxide
dissolves in rainwater to form carbonic acid/ as it moves
through the soil hydrogen ions and bicarbonate ions
o Step2: the hydrogen ions enter silicate rich minerals releasing
calcium ions
o Step3: the calcium and bicarbonate ions wash to the surface
and reach the ocean
o Step4: marine organisms incorporate calcium ions into their
shells and when these die their deposits will cement together
to form sedimentary rock limestone
 Nitrogen:
o Crucial for all organisms because it is part of biological
molecules such as proteins and nucleic acids
o Atmosphere 78% nitrogen gas (doesn’t usually combine with
other elements)
Nitrogen Cycle: the worldwide circulation of nitrogen from the abiotic
environment into organisms and back into the abiotic environment
 Bacteria driven cycle
o Step1: nitrogen fixation: the conversion of gaseous nitrogen to
ammonia
o Step2: nitrification: the conversation of ammonia to nitrate
and this step furnishes the bacteria with energy (nitrifying
bacteria)
o Ammonification: the conservation of biological nitrogen
compounds into ammonia and ammonium ions- begins when
organisms produce nitrogen contining waste products such as
urea of uric acid
o Denitrification- the reduction of nitrate to gaseous nitrogen
Phosphorous Cycle: the worldwide circulation of phosophorous from the
abiotic environment into organisms and back into he abiotic environment
 Land to sediments in the ocean and back to the land
Sulfur Cycle: the worldwide circulation of suflur from the abiotic
environment into organisms and back into he abiotic environment
 Most sulfur is underground in sedimentary rocks and minerals,
which over time erode to release sulfur-containing compounds
in the ocean
 Sulfur gases enter the atmosphere from natural sources in both
the ocean and the land
 Sea spray delievers sufates into the air as do forest fires and
dust stroms

Sulfur gases are minor parts in the environment and are not
long lived because theyr are reactive
 Sulfur plays a key role in plants and animals lives because the
plants absorb the sulfur through their roots and make it into
plant proteins then when the animals eat the plant they
incorporate that into animal proteins
 Bacteria drive this cycle
Hydrologic Cycle: the worldwide circulation of water from the abiotic
environment into organisms and back into he abiotic environment
 Water continuously circulates from the ocean to the atmosphere to
the land and back to the ocean
 Provides a renewable supply of purified water for organisms
 Results in a balance between water in the ocean, on the land, and in
the atmosphere
 atmosphere to land- precipitation (rain, snow, sleet, hail)
 when water evaporates from the ocean suface and from the soil,
steams, rivers it forms clouds in the atmosphere
 transpiration: the loss of water vapor from land plants, adds water
to the atmosphere
o 97% of the water a plants roots absorbe from the soil is
transported to the leaves where it is transpired
 estuaries- where fresh water meets the ocean
 runoff- the movement of water from land to rivers, lakes, welands,
and ultimately the ocean
 watershed- the area of land drained by runoff
 groundwater- fresh water stored in underground caverns and
porous layers of rock
Some Human Effects on Biogeochemical Cycles
 when people burn fossil fuels and combust wood carbon dioxide is
released into the atmosphere at a greater rate then the carbon cycle
can handle
o the rise of CO2 may cause human induced global warming
which will result in a rising sea level, changes in percipitaion,
death of forests, extinction of animals, and problems for
agriculture
 percipitaion washes nitrogen fertilizer in the rivers, lakes, and costal
areas where it will stimulate the growth of algae. Once the algae dies
they will take the space of the water and cause the fish to suffocate
and die/ nitrogen fertilizer will also contaminate groundwater
 nitrogen oxides: he conversation of high temperatures of
combustion to atmospheric nitrogen/ this will produce
photochemical smog, which is a mixture of air pollutants that injures
plant tissues, irritates eyes, and causes respiratory problems

acid depostition: when nitrogen oxides react with water in the
atmosphere to form acids that leave the atmosphere as this and cause
the pH of surface waters and soils to decrease
o linked to the declining animal populations in aquatic
ecosystems and altered soil chemistry on land
 humans affect the phosphorous cycle by accelerating the long term
loss of phosphorous from the land
 aerosols- tiny particles of air pollution consisting mostly of sulfates,
nitrates, carbon, mineral dusts, and fly ash
o produced from fossil fuel combustion and burning of forests
 albedo- the proportional reflectance of solar energy from the earth’s
surface, commonly expressed as a %
Temperature Changes with Latitude:
 earth’s temp variation is produced because the sun’s energy does not
reach all places uniformly
 the suns rays hit the earth vertically near the equator maming the
energy more concentrated and producing higher temps
Temperature Changes with Season:
 seasons determined by the earths inclination on its axis
 the inclination on its axis is 23.5 degrees from a line drawn
perpendicular to the orbital plane
 March-September: the northern hemisphere tilts towards the sun
 September-March: tilts away from the sun
 The atmosphere is a invisible layer of gases that envelop the earth:
oxygen and nitrogen main gases
 Atmosphere:
o Protects earths surface fro the sun ultraviolent radiation
o Allows some infrared radiation to penetrate the surface and
warm it: this interaction is responsible for weather and
climate
o Animals depend on this
Layers of the Atmosphere:
 Five layers:
o Troposphere: closest to the earth/height:10km/temp
decreases and increases -6 degrees Celcius/weather:
turbulent wind, storms, clouds
o Stratosphere: found above the troposphere/ little water but
no turbulence/temp: -45 to-75 degrees celcius/ in its lover
part is where jets fly/10 to 45 km/contains a layer of ozone
ciritical to life because it absorbs much of the suns
damaging rays
o Mesosphere: above the stratosphere/45-80 km/temp can
get as low as -138 degrees Celcius
o Thermosphere: above the mesosphere/80-500 km/very
hot/
o Exosphere: outer most layer/begins at 500km/ contunies
to thin until it converges with space
Atmosphere Circulation:
 As warm air raises it cools and sinks again
 The constant movement of air transfers heat from the equator
toward the poles and as the air returns it cools the land which it
passes
 Surface Wind:
o Winds: when the atmosphere exhibits complex horizontal
movements
 Results from differences in atmospheric pressure
and from the earth’s rotation
 Influenced by the rotation of earth
 Blow from places of high to low pressure
o Air pressure is a variable that changes with altitude,
temperature, and humidity
o Coriolis Effect: the influence of earth’s rotation, which
tends to turn fluids toward the right of the northern
hemisphere and toward the left in the southern
hemisphere/ deflects air currents in the direction of the
earths rotation/ greater at higher altitudes and negligible at
the equator
o Prevailing winds: major surface winds that blow more or
less continually
 Polar easterlies-winds that blow from the
northeast or southeast
 Westerlies: winds that blow from the multitudes or
from the northwest
 Trade winds: tropical winds that blow from the
northeast or from the southeast
Patterns of Circulation on the Ocean Front:
 Currents: the persistent prevailing winds blowing over the ocean
creates this
o the prevailing winds create gyres, circular ocean surrents
 the position of the landmass affects the ocean circulation
Vertical Mixing of Ocean Water:
 density-mass per unit/ affects deep ocean currents
 ocean conveyor belt affects regional and possibly global climate
Ocean Interactions with the Atmosphere
 El Nino-Southern Oscillation- a periodic, large scale warming of
surface waters of the tropical eastern Pacific Ocean that temporarily
alters both ocean and atmospheric circulation patterns
o Responsible for much of the Earth’s interannual climate
variability
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o Has global implications because it results in unusual weather
in areas far from the tropical Pacific
o Has effect on fisheries off south America
o El nino refers to the Christ child because the warming usually
reaches the fishing grounds in Peru just before chritamas
o Last one to two years
o Upwells: where deeper water comes the surface
o during one of these events the colder water below the surface
in the Eastern Pacific, and the warmer surface temperatures
and weat trade winds prevent upwelling
o alters global air currents directing unusual weather to areas far
from the tropical pacific
La Nina: occurs when the surface water temperature in the eastern
Pacific Ocean becomes cool and west bound trade winds become
unusually strong
o Often occurs after el nino
Weather: refers to the conditions in the atmosphere at a given place
and time
o Includes temperature, atmospheric pressures, precipitation,
cloudiness, humidity, and wind
Climate: the average weather conditions that occur in a place over a
period of time
o Determined by temperature and precipitation
Rain Shadows: dry conditions, often on a regional scale, that occur on
the leeward side of a mountain barrier
Tornado: a powerful, rotating funnel of air associated with severe
thunderstorms
o form when a mass of cool, dry air collides with warm, humid
air, producing a strong updraft of spinning air on the underside
of a cloud
o have more concentrated energy
Tropical Cyclones: giant, rotating tropical stroms with winds of at
least 119 km per hour
o Form as strong winds that pick up moischure over warm
surface waters and start to spin as a result of earths rotation
o hurricanes-atlantic
o typhoons-pacific
o cyclones-indian ocean
o during the summers when the waters are the warmest
Plate tectonics- the study of the processes by which the lithospheric
plates move over the atmosphere
Plate boundary-where two plates meet is the site of intense
geological activity
Volcanoes
o Magma: molten rock

o Lava- magama that reaches the surface
o Occur in three locations:
 Subduction zones (ring of fire)
 Spreading centers
 Above hot spots
o Hot spot: a rising plume of magma that flowed from an
opening
Earthquakes:
o Seismic waves: vibrations that spread through the rocks
rapidly in all directions
o Focus: where the earthquake begins
o Faults: fractures where rocks move forward and back
o Epicenter: directly above the surface at the earths surface
o Richter scale- the measure of the magnitude of energy released
by an earthquake