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Unit 02
Life on Earth I
Chapter 3
The Big Picture: Systems of Change
Systems and Feedback
System:
 A system can be defined as a group of
parts that work together to behave as a
whole. There are two types: .
A. Open System:
B. Closed System:
Q: Work with a partner to explain the following
Define each term and then explain which type of
system the earth is and why.
Two Types of Systems

Open System:
___________________________________
___________________________________
 ___________________________________
___________________________________


Closed System:

___________________________________
___________________________________
QUESTION
What type of system is the earth?
 Defend your answer.

Possible Answer
Systems and Feedback

Feedback

Occurs when the output of the system also serves as
an input, leading to further changes in the system. As
mentioned before ALL SYSTEMS RESPOND TO
INPUTS AND OUTPUTS. These responses are
known as feedback.
A. Negative Feedback
B. Positive Feedback
Q: Work with a partner to answer the following
Define each term WITH EXAMPLES and then explain
which is worse for the environment and why.
Types
of Feedback
 Negative
Feedback
___________________________________
___________________________________
 ___________________________________
___________________________________


Positive Feedback
___________________________________
___________________________________
 ___________________________________
___________________________________

Possible Answers
© 2008 John Wiley and Sons Publishers
© 2008 John Wiley and Sons Publishers
Environmental Unity

Environmental unity:

It is impossible to change only one thing;
everything affects everything else.
Uniformitarianism

Uniformitarianism:
The philosophical principle that processes
that operate today operated in the past.
 Observations of processes today can
explain events that occurred in the past and
leave evidence

“The present is the key to the past.”
Changes and Equilibrium in
Systems

Steady state:
A dynamic equilibrium
 Material or energy is entering and leaving
the system in equal amounts
 Opposing processes occur at equal rates

Changes and Equilibrium in
Systems

Average residence time:
The time it takes for a given part of the total
reservoir of a particular material to be
cycled through the sytem
 The equation for average residence time is:
ART = S/F

Q: Work with a partner to answer the following
Why is this important to APES? (hint: two BIG reasons)
Please use examples to illustrate your point.
Possible Answer
© 2008 John Wiley and Sons Publishers
Earth as a Living System

Biota:


All the organisms of all species living in an
area or region up to and including the
biosphere
Biosphere:
1.
2.
That part of a planet where life exists
The planetary system that includes and
sustains life
Ecosystem

Ecosystem:
A community of organisms and its local
nonliving environment in which matter
(chemical elements) cycles and energy
flows.
 Sustained life on Earth is a characteristic of
ecosystems
 Can be natural or artificial

Ecosystems

The Gaia Hypothesis:


Named for Gaia, the Greek goddess Mother Earth
States that the surface environment of the Earth,
with respect to such factors as the




atmospheric composition of gases
acidity-alkalinity of waters
Surface temperature
are actively regulated by the sensing, growth,
metabolism and other activities of the biota.
Or, life manipulates life the environment for the
maintenance of life.
Exponential Growth

Exponential growth:



Growth occurs at a constant rate per time period
Equation to describe exponential growth is:
Doubling time


The time necessary for the quantity being measured
to double.
Approximately equal to 70 divided by the annual
percentage growth rate
Why Solving Environmental
Problems Is Often Difficult
Exponential growth
1.
•
The consequences of exponential growth and its
accompanying positive feedback can be dramatic
Lag time
2.
•
•
The time between a stimulus and the response of a system
If there is a long delay between stimulus and response,
then the resulting changes are much more difficult to
recognize.
Irreversible consequences
3.
•
Consequences that may not be easily rectified on a human
scale of decades or a few hundred years.
Chapter 5
The Biogeochemical Cycles
How Chemicals Cycle
Biogeochemical Cycle:
Global Cycles recycle nutrirents through the earth’s air, land water,
and living organisms and, in te process, connect the past, present and
future forms of life. The complete path a chemical takes through
the four major components – or reservoirs – of Earth’s systems.
Bio(life)geo(atmosphere, rock, water and/or soil)
1.
2.
3.
4.
Atmosphere – atmos refers to vapor so in this case we mean the
gases in the environment
Hydrosphere – hydro refers to “water” so in this case we mean
oceans, rivers, lakes, groundwater, and glaciers
Lithosphere – litho means “stone” so in this case we mean rocks and
soils
Biosphere – bio means “life” so in this case we mean living things such
as plants and animals
Chemical Reactions

Ch emical reaction:
The process in which new chemicals are
formed from elements and compounds
through chemical change
 Review your basic chemistry!! Pages 78-80

Q: Write down the formula for photosynthesis and
explain why this is important.
Photosynthesis
sunglight
6CO2 + 6H2O --------> C6H12O6 + 6O2
This could be said to be one of the most
important chemical reactions to modern
life on the planet. This is where plants
(and bacteria & protists( convert energy
from the sun into a form other organisms
can use. Additionally this is where much
of our oxygen is produced
Biogeochemical Cycles and Life:
Limiting Factors

Macronutrients


Elements required in large amounts by all life
Include the “big six” elements that form the fundamental
building blocks of life:
carbon
hydrogen
nitrogen

Micronutrients

Elements required either in



oxygen
phosphorus
sulfur
small amounts by all life or
moderate amounts by some forms of life and not all by others
Limiting factor

When chemical elements are not available at the right times,
in the right amounts, and in the right concentrations relative to
each other
Assignment
1: Nitrogen Cycle
2: Carbon Cycle
3: Rock Cycle
4: Phosphorus Cycle
5: Sulfur Cycle
6: Water Cycle
Include:
1. Drawing of Cycles
2. List of Key Steps
3. Why is your element
etc important
4. How are humans
impacting each cycle
and why should we
care?
Assignment: Create a book of the cycles. Please explain how the cycle(s)
work, why they are important and how humans are influencing them.
Bonus Cycles: Carbon-Silicate Cycle Calcium Cycle Tectonic Cycle
The Nitrogen Cycle
Importance: Nitrogen is required by all living things – in protein, nucleic acids, chlorophyll etc.
Summary:

Cycle responsible for moving important nitrogen components through the biosphere and other Earth
systems. Note: most nitrogen is stored in the atmosphere as N2. In this form organisms cannot use or
process N. Different types of bacteria help recycle nitrogen through the earth’s air, water, soil and living
organisms.
Steps:

Nitrogen fixation:

The process of converting inorganic, molecular nitrogen in the atmosphere to ammonia or nitrate (ex. via
lightening, bacteria, industry).

Plants convert fixed nitrogen compounds to proteins.

Animals obtain this nitrogen by eating plants or by eating herbivores that eat plants.

Death – nitrogen compounds are returned to the soil during decomposition.

Nitrification – The process of bacteria converting ammonia (NH3) (which can be toxic to plants etc) to nitrites (also
toxic to plants) (NO2-) and then finally to nitrates (NO3-).

Denitrification - The process of releasing fixed nitrogen back to molecular nitrogen N2. Also done by bacteria
Human Impact:

Humans have had a large impact on this cycle due to agricultural fertilization, burning of fossil fuels, wastewater
etc. This has caused several problems including major issues in our waters such as eutrophication which is the
accumulation of dissolved nutrients in water. This can have serious effects on the ecosystems in the areas
where is is happening. In effect we are adding large amounts of nitrogen-containing compounds to the earth’s air
and water and removing nitrogen from the soil.
1.
2.
3.
4.
5.
6.
We add large amounts of nitric oxide (NO) into the atmosphere creating nitric acid (HNO3)  acid precipitation
We also add N2O to the atmosphere because of livestock waste. This can cause ozone problems and lead to warming effects
We contaminate ground water with NO3- ions from fertilizers
We release large quantities of nitrogen stores in souls and plants when we destroy forests, wetlands etc.
We upset aquatic ecosystems by adding excess nitrates to bodies of water
We remove much needed nitrogen from topsoil when we harvest nitrogen rich crops, irrigate, burn etc.
The Sulfur Cycle




Importance: Sulfur is important to living things because it is one of the main components of proteins.
Summary: Sulfur cycles through the earth’s air, water, soil and living organisms.
Key Steps:

The main source of sulfur is the lithosphere (the earth’s crust)

Sulfur is taken up by plants

Plants are eaten by animals – travels through food chain

Sulfur is also found in the atmosphere. It usually gets there by several different paths

Volcanic Eruptions

Decomposition – yay dead things!

Humans – enters as hydrogen sulfide H2S

Oceans via gas exchange (SO is transformed by organisms such as phytoplankton into organic
forms)
Human Impact:

Burning coal and oil, refining oil and producing some metals from ores add sulfur dioxide into the
atmosphere.

acid precipitation!!!: When hydrogen sulfide enters the atomosphere it is immediately oxidized to
create SO2. This is an issue because when it combines with water it creates an acid: H2SO4 (Sulfuric
Acid)This is a weak acid, which has numerous effects when taken up by plants, when it enters lakes
etc. It also has caused some seriously problems with erosion.

Humans also add additional sulfur through pesticides and some fertilizers though this is not as
common as the sulfur released through the burning of fossil fuels such as coal and combustion
engines.
1.
2.
3.
We burn sulfur containing coal and oil to produce electric power
We refine sulfur containing petroleum to make gasoline, heating oil and other useful products
We convert sulfur containing metallic mineral ores into free metals such as copper, lead an zinc
which releases a lot of sulfur dioxide into the atmosphere causing acid precipitation.
The Phosphorus Cycle


Importance: The phosphorus cycles fairly slowly through the earth’s water, soil
and living organisms. Part of important molecules such as DNA and ATP as well as
part of necessary ions. It is also an essential element for life and often is a limiting
nutrient for plant growth.
Summary:





Involves the movement of phosphorus throughout the biosphere and lithosphere
Important because phosphorus Most phosphorus is stored in the Earth’s rocks/soils and is
released to water via erosion and weathering
Plants take up phosphorus in aquatic and terrestrial ecosystems and animals eat the
plants; returning the phosphorus to the soil via urine, feces, and death.
Phosphorus does NOT exist in the atmosphere!!
Human Impact: We remove large amounts of phosphate from the earth to make
fertizizerm reduce phosphorus in tropical soils bu clearing forests and then we add
excess phosphates into aquatic systems. This occurs largely by the use of
commercial synthetic fertilizers. It will often enter the water supplies and give an
unwanted increase in nutrients. Sometimes it will also enter the water supply due
to wastewater contamination.
We mine large quantities of phosphate rock to make fertilizers and some detergents.
2. We reduce the available phosphate in tropical forests.
3. We disrupt aquativ systems with phosphates from runoff of animal wastes, fertilizers and
discharges from sewage treatment systems
Note: Since 1900 human activities have increased the natural rate of phosphorus release into
the environment about 3.7-fold.
1.
The Hydrologic Cycle: The Water Cycle




Importance: This cycle is important for many reasons. Biologically water is necessary for all life. The water
cycle is also necessary for the rock cycle etc. This cycle allows water to continually be recycled 
Summary:

A vast global cycle collects, purifies, distributes and recycles the earth’s fixed supply of water. The
transfer of water from the oceans to the atmosphere to the land and back to the oceans. Includes:
Steps:

Evapotranspiration

Evaporation - (liquid to gas) of water from the oceans and from land. May also occur as runoff
from streams, rivers, and sub-surface groundwater

Transpiration: liquid to gas from plants

Condensation – (gas to liquid) leads to the next step

Precipitation - (water in any form falling from atmosphere) on land

Infiltration – entry of water into the earth’s surface

Percolation – when water descends through soil and rock – under root zone

Runoff – water moves from surface to bodies of water
Human Impact: We alter the water cycle by withdrawing large amounts of freshwater, clearing vegetation and
erodiing sols, polluting surface and underground water, and contributing to climate change. Rates of the cycle
are also changing due to human behavior. Specifically:
1.
We withdraw water faster than it is replenished
2.
We clear vegetation from land for agriculture, mining, roads, building etc causing runoff, reduced
infiltration – all of these contribute to flooding.
3.
We add nutrients (see other cycles) and other pollutants to our water. It can impair or destroy ecological
processes that naturally purify water
4.
The Earth’s water cycle is speeding up due to climate change (Curry 2003). This could cause an
increase in severe weather. It could also act as a positive feedback in terms of global warming.
(increases in water vapor increase temperatures, which allows more water to evaporate causing
increases in temperature and so on.)
© 2008 John Wiley and Sons Publishers
The Carbon Cycle

Importance: Carbon is the element that anchors all organic substances
 Summary: All life on earth is based on carbon.Carbon cycles through the
earth’s air, water, soil and living organisms and depends on
photosynthesis and respiration. Carbon combines with and is chemically
and biologically linked with the cycles of oxygen and hydrogen that form
the major compounds of life. Steps: Carbon is cycled between biotic and
abiotic factors






Burning – carbon released to atmosphere
Photosynthesis – carbon from atmosphere trapped in plants
Respiration – carbon released to atmosphere
Death – carbon returned to soil
Fossil fuels created after millions of years of being buried.
Human Impacts: Burning of fossil fuel and clearing photosynthesizing
vegetation faster than it is replaced can increase the earth’s average
temperature by adding excess CO2 into the atmosphere. CO2 is an
important greenhouse gas.
1.
2.
3.
We are cutting down the trees and plants that absorb CO2
We add large amounts of CO2 by burning fossil fuels
Both of these things enhance the earth’s NATURAL greenhouse effect
© 2008 John Wiley and Sons Publishers
The Carbon Cycle:
Unanswered Issues

The Missing Carbon Sink

Substantial amounts of carbon dioxide
released into the atmosphere but apparently
not reabsorbed and thus remaining
unaccounted for
The Rock Cycle



Summary:

The rock cycle contains umerous processes that produce rocks and soils

Depends on other cycles:
 Tectonic cycle for energy
 Hydrologic cycle for water

Rock is classified as
 Igneous: Formed from the cooling of molten rock.
 A. Volcanic igneous rocks formed from molten rock that cooled quickly on or
near the earth's surface.
 B. Plutonic igneous rocks are the result of the slow cooling of molten rock
far beneath the surface.
 Sedimentary: Formed in layers as the result of moderate pressure on accumulated
sediments.
 Metamorphic: Formed from older "parent" rock (either igneous or sedimentary)
under intense heat and/or pressure at considerable depths beneath the earth's
surface.
Importance: Weathering produces soils. Soils are a mix of small rock particles as well as
organic matter.
Human Impact: Human activities such as overgrazing, farming, urbanization and
deforestation have increased erosion thereby harming a non-renewable resource (as soil
production is a SLOOOOW process). Global food production leads to an annual loss of 25
billion tons of topsoil.
© 2008 John Wiley and Sons Publishers
Other Cycles
Tectonic Cycle

Tectonic cycle:


Involves creation and destruction of the
solid outer layer of Earth, the lithosphere
Plate tectonics:
The slow movement of these large
segments of Earth’s outermost rock shell
 Boundaries between plates are geologically
active areas

Tectonic Cycle: Plate Boundaries
Tectonic Cycle – creation and destruction of the lithosphere (the
solid outer layer of the earth)
 Plate Tectonics – The slow movement of the large segments of
the earth’s outermost rock shell.
Three types of plate boundaries:
1. Divergent plate boundary:



2.
Occurs at a spreading ocean ridge, where plates are moving away
from one another
New lithosphere is produced (seafloor spreading)
Convergent plate boundary

Occurs when plates collide

3.
Produces linear coastal mountain ranges or continental mountain
ranges
Transform fault boundary

Occurs where one plate slides past another

San Andreas Fault in California
The Carbon-Silicate Cycle

The carbon-silicate cycle:


A complex biogeochemical cycle over time scales
as long as one-half billion years.
Includes major geological processes, such as:





Weathering
Transport by ground and surface waters
Erosion
Deposition of crustal rocks
Believed to provide important negative feedback
mechanisms that control the temperature of the
atmosphere.
© 2008 John Wiley and Sons Publishers
The Geologic Cycle

The Geologic Cycle:
The processes responsible for formation
and change of Earth materials
 Best described as a group of cycles:

Tectonic
 Hydrologic (Water)
 Rock
 Biochemical (Carbon, Nitrogen, Phosphorus,
Sulfur etc)
