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 (phosphate-containing 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

• 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

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

• 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)

Low concentration Higher Reflection Low Temperature

From (a) to (c)

In diagram below

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 – Left side of diagram

• 2. Winds blow from high to low pressure – Right side of diagram

Low

Low

Low

High

High

High

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

Trade winds

Westerlies

2. Very little land in the Southern Hemisphere

1. Large landmasses in the Northern Hemisphere help to dictate ocean currents and flow

D. Position of Landmasses

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