Download chapter 5 ecosystems and the physical environment

CHAPTER 5
ECOSYSTEMS AND THE PHYSICAL
ENVIRONMENT
I. Cycling of Materials
• A. Matter moves between
ecosystems, environments,
and organisms
• B. Biogeochemical cycling
involves
– 1. Biological, geologic and
chemical interactions
• C. Five major cycles:
– 1. Carbon, Nitrogen,
Phosphorus, Sulfur and Water
(hydrologic)
D. The Carbon Cycle
– 1. photosynthesis – plants, algae, and certain
bacteria remove carbon dioxide from the air and
fix it into chemical compounds such as sugar.
– 2. cellular respiration – compounds from
photosynthesis are used as fuel – returns carbon
dioxide to the atmosphere
– 3. fossil fuels – carbon is not always recycled back
to the abiotic environment immediately – stored
as fossil fuels
– 4. combustion – carbon is returned to the
atmosphere by burning
– 5. human-induced changes to the carbon cycle
• a. industrial revolution – increasing in the burning of
fossil fuels
• b. more wood being burned
• c. burning of large sections of tropical forests
• d. more carbon dioxide is in the atmosphere – in the
1700s there was .029% in the atmosphere and now
there is 0.038% in the atmosphere – it is expected to
rise to .06% by the middle of this century
E. The Nitrogen Cycle
– 1. nitrogen is essential for proteins and nucleic
acids
– 2. nitrogen cycle is composed of five steps
• a. nitrogen fixation – conversion of gaseous nitrogen to
ammonia – nitrogen fixing bacteria (including
cyanobacteria) carry out biological nitrogen fixation in
soil and aquatic environments – also found on the roots
of plants (mutualism)
• b. nitrification – nitrifiying bacteria - conversion of
ammonia or ammonium to nitrate – soil bacteria
perform this in two steps
– (1) soil bacteria convert ammonia or ammonium to nitrite
– (2) other bacteria oxidize nitrite to nitrate
• c. assimilation – plant roots absorb nitrate, ammonia,
or ammonium – incorporate the nitrogen into plant
proteins and nucleic acids – when animals consume
plant tissues, they assimilate nitrogen by taking in plant
nitrogen compounds (amino acids) and converting
them to animal compounds (proteins)
• d. ammonification – conversion of biological nitrogen
compounds into ammonia and ammonium ions –
produce wastes such as urea and uric acid – decompose
to release the nitrogen into the environment as
ammonia – performed by ammonifying bacteria
• e. denitrification – reduction of nitrate to gaseous
nitrogen – reverse the action of nitrogen-fixing and
nitrifying bacteria
– 3. Human-induced changes to the nitrogen cycle
• a. fertilizers - precipitation washes nitrogen fertilizer
into rivers, lakes, and coastal areas, where it stimulates
the growth of algae – as the algae decomposes,
bacteria increase and rob the environment of oxygen –
fish and other aquatic organisms suffocate
• b. combustion of fossil fuels – photochemical smog –
injures plant tissues, irritates eyes, and causes
respiratory problems
• c. acid deposition – nitrogen oxide – reacts with water
to form acid rain – declining animal populations in
aquatic ecosystems and altered soil chemistry on land
F. The Phosphorus Cycle
– 1. phosphorus cycles from the land to sediments
in the ocean and back to the land
– 2. as water runs over apatite (phosphatecontaining minerals) it gradually wears away the
surface and carries off inorganic phosphate
molecules – releases phosphorus into the soil
– 3. plant roots absorb it – used for nucleic acids
and ATP
– 4. animals obtain phosphate from the food they
eat
– 5. phosphorus is released by decomposers back
into the soil
– 5. human-induced changes to the phosphorus
cycle
• a. accelerate the long-term loss of phosphorus from the
land
• b. the addition of excess phosphorus from fertilizer or
sewage can contribute to enrichment of the water and
lead to undesirable changes
G. The Sulfur Cycle
– 1. most sulfur is underground in sedimentary
rocks and minerals – over time erodes to release
sulfur-containing compounds into the ocean
– 2. sea spray delivers sulfates into the air
– 3. forest fires and dust storms are rich in calcium
sulfate which enters into the air
– 4. volcanoes release both hydrogen sulfide
(poisonous gas that smells of sulfur) and sulfur
oxides (include sulfur dioxide and sulfur trioxide)
– 5. hydrogen sulfide reacts with oxygen to form
sulfur oxides
– 6. sulfur oxides react with water to form sulfuric
acid
– 7. sulfur is found in small amounts in proteins
– 8. plant roots absorb sulfate and assimilate it by
incorporating the sulfur into plant proteins
– 9. animals assimilate sulfur when they consume
plant proteins and convert them to animal
proteins
– 10. marine algae release large amounts of a
compound that bacteria convert to dimethyl
sulfide (DMS) which is released into the
atmosphere
– 11. DMS is converted to sulfate which is deposited
in the ocean
– 12. bacteria drive the sulfur cycle – in wetlands
where there is very little oxygen, bacteria convert
sulfates to hydrogen sulfide gas
– 13. Human-induced changes to the sulfur cycle
• a. coal and oil contain sulfur so when these fuels are
burned, sulfur dioxide is released to the atmosphere
which leads to acid deposition
• b. smelting of sulfur-containing ores of such metals as
copper, lead, and zinc release sulfur dioxide
• c. pollution abatement such as scrubbers has reduced
the amount of sulfur emissions in highly developed
countries but globally emissions continue to increase
H. The Water (Hydrologic) Cycle
– 1. evaporation and transpiration – adds water to
the atmosphere
– 2. movement of water
• a. runoff – movement of water from land to rivers,
lakes, wetlands, and the ocean
• b. watershed – the area of land drained by runoff
• c. groundwater – water percolates, or seeps, downward
in the soil – fresh water is stored in underground
caverns and porous layers of rock – may reside in the
ground for hundreds to thousands of years – eventually
it supplies water to the soil, vegetation, streams, rivers,
and the ocean
– 3. condensation – cloud formation
– 4. ¾ of the water in the atmosphere returns to the
ocean as precipitation – the rest falls on land
– 5. human-induced changes to the hydrologic cycle
• a. air pollution weakens the hydrologic cycle
– (1) aerosols – tiny particles of air pollution consisting mostly
of sulfates, nitrates, carbon, mineral dusts, and smokestack
ash which are produced by burning fossil fuels – enhance the
scattering and absorption of sunlight in the atmosphere and
cause clouds to form – cause a warming of the atmosphere -
• b. climate change – increasing glacial and polar ice-cap
melting – also increases evaporation in some areas
II. Solar Radiation

A. Sun provides energy for life, powers biogeochemical cycles,
and determines climate – nuclear fusion reaction releases
energy in the form of electromagnetic radiation (visible light,
infrared radiation, and ultraviolet radiation
• 1. Albedo
– a. The reflectance of solar
energy off earth’s surface
– b. Dark colors = low albedo
• Forests and ocean
– c. Light colors = high albedo
• Ice caps
• B. Temperature Changes with Latitude
– 1. Solar energy does not hit earth uniformly
– 2. Due to earth’s spherical shape and tilt
Equator (a)
High concentration
Little Reflection
High Temperature
Closer to Poles (c)
From (a) to (c)
In diagram below
Low concentration
Higher Reflection
Low Temperature
C. Temperature Changes with Season
• 1. Seasons
determined by
earth’s tilt
(23.5°)
• 2. Causes each
hemisphere to
tilt toward the
sun for half the
year

3. Northern Hemisphere tilts towards the sun
from March 21- September 22 (warm season)
III. The Atmosphere
• A. Content
– 1. 21% Oxygen
– 2. 78% Nitrogen
– 3. 1% Argon, Carbon dioxide,
Neon and Helium
• B. Density decreases with
distance from earth
• C. Shields earth from high
energy radiation
D. Atmospheric Layers
•
•
•
1. Troposphere (0–10km)
– a. Where weather occurs
– b. Temperature decreases with
altitude
2. Stratosphere (10–45km)
– a. Temperature increases with
altitude- very stable
– b. Ozone layer absorbs UV
– c. steady wind but no turbulence
– d. little water
3. Mesosphere (45–80km)
– a. Temperature decreases with
altitude
– Lowest temp in the atmosphere
•
4. Thermosphere (80–500 km)
– a. Gases in thin air absorb x-rays and
short-wave UV radiation = very hot
– b. Source of aurora – colorful display
of lights in dark polar skies produced when charged particles
from the sun hit oxygen or nitrogen
molecules
– c. long distance communication –
reflects outgoing radio waves back to
earth
•
5. Exosphere (500km and up)
– a. Outermost layer
– b. Atmosphere continues to thin until
converges with interplanetary space
E. Atmospheric Circulation
• A. Near Equator
– 1. Warm air rises, cools and
splits to flow towards the
poles – convection
– 2. ~30° N & S sinks back to
surface
– 3. Air moves along surface
back towards equator
• B. This occurs at higher
latitudes as well
– 1. Moves heat from equator
to the poles
F. Surface Winds
• 1. Large winds due in
part to pressures
caused by global
circulation of air
High
Low
High
Low
– Left side of diagram
• 2. Winds blow from
high to low pressure
High
Low
– Right side of diagram
High
G. Coriolis Effect
• 1. Earth’s rotation influences direction of wind
– a. Earth rotates from East to West
– b. Deflects wind from straight-line path
• 2. Coriolis Effect
– a. Influence of the earth’s rotation on movement of
air and fluids
– b. Turns them Right in the Northern Hemisphere
– Turns them Left in the Southern Hemisphere
Coriolis Effect
IV. Patterns of Ocean Circulation
• A. Prevailing winds produce ocean currents
and generate gyres which are circular ocean
currents
• B. Example: the North Atlantic Ocean
– 1. Trade winds blow west
– 2. Westerlies blow east
– 3. Creates a clockwise gyre in the North Atlantic
• C. Circular pattern influenced by coriolis effect
Patterns of Ocean Circulation
Westerlies
Trade winds
D. Position of Landmasses
1. Large landmasses
in the Northern
Hemisphere help to
dictate ocean
currents and flow
2. Very little land in
the Southern
Hemisphere
E. Vertical Mixing of Ocean Water
• 1. varying density affects deep-ocean currents
• 2. cold, salty water is denser than warmer, less
salty water
• 3. colder, salty ocean water sinks and flows
under the warmer, less salty water and creates
currents
• 4. the Coriolis effect is more pronounced at
greater depths
• 5. ocean conveyor belt – shows shallow and
deep currents
• 6. the Atlantic Ocean gets its cold, deep water
from the Arctic Ocean and the Pacific and
Indian Oceans get theirs from the water
surrounding Antarctica
• 7. scientists are concerned that human
activities may unintentionally affect the link
between the ocean conveyor belt and global
warming
Vertical Mixing of Ocean
V. Ocean Interaction with
Atmosphere - ENSO
• A. the ocean and the atmosphere are strongly linked
with wind from the atmosphere affecting the ocean
currents and heat from the ocean affecting atmospheric
circulation
• B. El Niño-Southern Oscillation (ENSO)
– 1. Periodic large scale warming of surface waters of
tropical E. Pacific Ocean
• C. Normal conditions
– 1. westward blowing trade winds keep warmest water
in western Pacific
• D. ENSO conditions – occur every 3 to 7 years and last 1-2
years
– 1. trade winds weaken and warm water expands eastward
to South America increasing temperatures in the East
Pacific
– 2. ocean currents which normally flow westward in this
area, slow down, stop altogether, or even reverse and go
eastward
– 3. devastating effects on the fisheries off South America –
normally, the colder, nutrient-rich deep water below the
surface upwells along the coast in response to trade winds
– with ENSO the trade winds are weak and upwelling is
prevented – decrease in marine fish
– 4. shrimp and scallops thrive during an ENSO
event
– 5. ENSO alters global air currents, directing
unusual and sometimes dangerous weather to
areas far from the tropical Pacific
– 6. TAO/TRITON array – consists of 70 moored
buoys in the tropical Pacific Ocean – they collect
oceanic and weather data – helps predict ENSO
events as much as 6 months in advance
ENSO Climate Patterns
VI. Weather and Climate
• A. Weather
– 1. The conditions in the atmosphere at a given
place and time
– 2. Temperature, precipitation, cloudiness, etc.
• B. Climate
– 1. The average weather conditions that occur in
a place over a period of years
– 2. 2 most important factors: temperature and
precipitation
C. Rain Shadows
• 1. Mountains force humid air to rise
• 2. Air cools with altitude, clouds form, and
precipitation occurs (windward side)
• 3. Dry air mass moves leeward side of
mountain
D. Tornadoes
• 1. Powerful funnel of air associated with a
severe thunderstorm
• 2. Formation
– a. Strong updraft of spinning air forms as mass of
cool dry air collides with warm humid air
– b. Spinning funnel becomes tornado when it
descends from cloud
• 3. Wind velocity = up to 300 mph
• 4. Width ranges from 1m to 3.2 km
E. Tropical Cyclone
• A. Giant rotating tropical storms
• B. Wind > 119 km per hour
• C. Formation
– 1. Strong winds pick up moisture over warm
surface waters and starts to spin due to Earth’s
rotation
– 2. Spin causes upward spiral of clouds
• D. Many names:
– Hurricane (Atlantic), typhoon (Pacific), cyclone
(Indian Ocean)
VII. Internal Planetary Processes
• A. Layers of the
earth
– 1. Lithosphere
• a. Outermost rigid
rock layer
composed of
plates
– 2. Asthenosphere
• a. Lower mantle
comprised of hot
soft rock
• B. Plate Tectonics- study of the processes
by which the lithospheric plates move over
the asthenosphere
• C. Plate Boundary - where 2 plates meet
– 1. Divergent – plates move away
– 2. Convergent – plates come together
– 3. Transform – plate move along each other
Plates and Plate Boundaries
D. Earthquakes
• 1. Caused by the release of accumulated energy
as rocks in the lithosphere suddenly shift or
break
– a. Occur along faults
– b. Energy released as seismic wave
E. Tsunami
• 1. Giant undersea wave caused by an
earthquake, volcanic eruption or landslide
– a. Travel > 450 mph
• 2. Tsunami wave may be 1m deep in ocean
– a. Becomes 30.5m high on shore
• 3. Magnitude 9.3 earthquake in Indian Ocean
– a. Triggered tsunami that killed over 230,000
people in South Asia and Africa