Transcript Chapter 3 Environmental Systems: Chemistry,

Chapter 3
Environmental
Systems:
Chemistry,
Energy, and
Ecosystems
PowerPoint® Slides
prepared by
Jay Withgott and Heidi
Marcum
This lecture will help you
understand:
• The nature of environmental
systems
• The fundamentals of
environmental chemistry
• The molecular building blocks of
organisms
• Energy and energy flow
• Photosynthesis and respiration
• Ecosystems and interactions
• Fundamentals of landscape
ecology
• Carbon, phosphorus, nitrogen,
and water cycles
What is a Dead Zone?
What causes it?
Where are they located?
Its Not Just Us
Central Case: The Gulf of
Mexico’s “Dead Zone”
• Gulf of Mexico used to bring in 600 million
kg/year shrimp, fish, and shellfish
• Gulf “dead zone”: a region of water so depleted
of oxygen that marine organisms are killed or
driven away
• In 2000, this zone encompassed 22,000 km2
(8,500 mi2) — an area larger than New Jersey.
• Hypoxia: low concentrations of dissolved
oxygen water
– Caused by fertilizer, runoff, sewage
• The U.S. government proposed that farmers
The Earth’s systems
• System: a network of relationships among
components that interact with and influence one
another
– Exchange of energy, matter, or information
– Receives inputs of energy, matter, or information,
processes these inputs, and produces outputs
• Feedback loop: a system’s output serves as
input to that same system
– A circular process
Negative feedback loop
• Negative feedback loop: output resulting from
a system moving in one direction acts as an
input that moves the system in the other
direction
–
–
–
–
Input and output neutralize one another
Stabilizes the system
Example: body temperature
Most systems in nature
Positive feedback loop
• Positive feedback loop: instead of stabilizing a
system, it drives it further toward an extreme
• Examples: erosion
• Rare in nature
– But are common in natural systems altered by
humans
Cntd
•
Negative Feedback Loop:
A change in which the variable being regulated brings about a response that moves
the variable in the "opposite direction". for example you are inside and at normal body
temperature(variable) then you go outside into the cold and your body temp begins to
decrease(unintended event), your body responds by causing events that raise your
temperature(intentional change) "back up to its original value"(raising your temp that
was falling). this is mostly seen in homeostasis and you dont have to go outside for
your body to do this because it is constantly happening all the time.
Positive Feedback loop:
this type of feedback loop accelerates a process and usually has no obvious means
of being slowed or stopped. Think of an avalanche that started as a small snowball
rolling down a steep hill. One example is child birth in mammals. A positive feedback
loop occurs when a baby's head is pushed against the birth canal. the nerve signals
from smooth muscle cells of the birth canal send info to the brain which then triggers
a hormone release from the petuitary glands. the hormones then cause those "same
smooth muscle cells" in the birth canal to contract with more force, which causes
more signals to be sent to the brain and so on until the fetus is delivered
Activity:
• Define the following:
– Ecosystem
– Positive feedback loop
– Negative feedback loop
– Hypoxia
• Be sure to have your writing assignment
complete by tomorrow (section 1, ch 3)
– I will be checking it
Systems Approach
• Looking at ENTIRE situation
• Holistic approach
– Dead fish:
• Look at entire ecosystem for cause
– Amount of dissolved O2
– Health of other fauna
– Human impacts
– Cancer:
• Look at possible factors to form plan of action
– Diet
– Exercise
– Alcohol intake
Environmental systems interact
• Natural systems are divided into
categories
– Lithosphere: rock and sediment
– Atmosphere: the air surrounding the planet
– Hydrosphere: all water on earth
– Biosphere: the planet’s living organisms
• Categorizing systems allows humans to
understand earth’s complexity.
– Most systems overlap
The Gulf of Mexico: a systems
perspective
Very high levels of nutrients such as nitrogen and
phosphorus from a variety of sources cause the
abnormally low levels of oxygen in the Gulf of Mexico.
Where it Begins
Eutrophication in the Gulf
• Nutrients (nitrogen and phosphorus) from
various Midwestern sources enter the
Mississippi River, which causes….
• Phytoplankton (microscopic algae and bacteria)
to grow, then…
• Bacteria eat dead phytoplankton and wastes
and deplete oxygen, causing…
• Fish and other aquatic organisms to suffocate
• Eutrophication: the process of nutrient
overenrichment, blooms of algae, increased
production of organic matter, and ecosystem
degradation
Eutrophication
Activity
• Read article Independently and Quietly in class
• AFTER everyone in class has completed the
reading assignment, you can work in pairs to
complete the writing assignment. We will discuss
your points tomorrow in class
• Look at the different projects I have created for
you. You will be responsible for completing one
on the due date.
• BRING IN TEXTBOOKS TOMORROW 
Chemistry:
Crucial for Understanding…
• Any environmental issue:
– How gases contribute to global climate
change
– How pollutants cause acid rain
– The effects of chemicals on the health of
wildlife and people
– Water pollution
– Wastewater treatment
– Hazardous waste
– Atmospheric ozone depletion
– Energy issues
Chemical building blocks
• Matter: all material in the universe that has
mass and occupies space
– Can be transformed from one type of substance
into others
– But it cannot be destroyed or created, which is…
– The law of conservation of matter
• Helps us understand that the amount of matter stays
constant
• Recycled in nutrient cycles and ecosystems
Chemical building blocks
• Element: a fundamental type of matter,
with a given set of properties
– Chemists recognize 92 elements in nature and
20 artificially created ones.
– Elements abundant in nature: carbon,
nitrogen, hydrogen and oxygen
– Periodic table of the elements summarizes
information on the elements
Elements are composed of
atoms
– Atoms: the smallest components that maintain
an element’s chemical properties
– The atom’s nucleus has protons (positively
charged particles) and neutrons (particles
lacking electric charge).
– Atomic number: the atom’s number of protons
– Electrons: negatively charged particles
surrounding the nucleus that balance the
positively charged protons
– Atoms may also gain or lose electrons to
become ions —electrically charged atoms.
The structure of an atom
Chemical building blocks
• Isotopes: atoms with differing
numbers of neutrons
– Mass number: the number of
protons and neutrons
– Isotopes of an element behave
differently.
– Some isotopes are radioactive.
• They decay until they become nonradioactive stable isotopes.
• Emit high-energy radiation
Radioactive decay
• Half-life: the amount of time it takes for onehalf of the atoms to give off radiation and
decay
– Different radioscopes have different half-lives
ranging from fractions of a second to billions of
years.
– Uranium-235, used in commercial nuclear power,
has a half-life of 700 million years.
Molecules and compounds
• Molecules: combinations of two or more
atoms: Covalently Bonded
– Oxygen gas: O2
• Compounds: a molecule composed of atoms
of two or more different elements
– Water: two hydrogen atoms bonded to one
oxygen atom (H20)
– Carbon dioxide: one carbon atom with two
oxygen atoms (CO2)
• Solutions: no chemical bonding, but is a
mixture of substances (i.e., blood, ocean
Hydrogen ions determine acidity
• The pH scale ranges from 0 to
14 and quantifies the acidity or
basicity of solutions.
– Acidic solutions have a pH less
than 7.
– Basic solutions have a pH greater
than 7.
– Neutral solutions have a pH of 7
(i.e., pure water).
• A substance with pH of 6
contains 10 times as many
hydrogen ions as a substance
with pH of 7.
Activity:
• Outline pages 49-56
Organic Compounds
• Organic compounds: carbon atoms joined by
bonds that may include other elements
– Such as nitrogen, oxygen, sulfur, and phosphorus
• Hydrocarbons: contain only carbon and
hydrogen
– Make up fossil fuels
– The simplest hydrocarbon is methane (natural gas)
– Can be a gas, liquid, or solid
Macromolecules: life’s building
blocks
• Polymers: long chains of repeated molecules
– The building blocks of life
• Macromolecules: large-size molecules
– Three types of polymers are essential to life:
• Proteins
• Nucleic acids
• Carbohydrates
– Lipids are not polymers, but are also essential.
Proteins
• Produce tissues, provide structural
support, store energy, and transport
substances
– Made up of chains of amino acids
– Animal proteins generate skin, hair, muscles,
and tendons
– Some function as components of the immune
system
– Can serve as enzymes — molecules that
promote chemical reactions
A special process involving
proteins
• Nucleic acid: directs the production of proteins
– Deoxyribonucleic acid (DNA) and ribonucleic
acid (RNA) carry the hereditary information of
organisms.
• Long chains of nucleotides that contain sugar, phosphate,
and a nitrogen base
• Genes: regions of DNA that code for
proteins that perform certain functions
Carbohydrates and lipids
• Carbohydrates: atoms of carbon, hydrogen,
and oxygen
– Sugars: simple carbohydrates, 3-7 carbons long
• Glucose: provides energy for cells
– Complex carbohydrates build structures and store
energy
• Starch: used by plants to store energy
• Animals eat plants to acquire starch.
• Cellulose of plants and shells of insects
• Lipids: a chemically diverse group of
compounds grouped together because they
don’t dissolve in water
– Energy, cell membranes, structural support, and
hormones
Cells compartmentalize
macromolecules
• Cell: the basic unit of life’s organization
• Eukaryotes: contain a membrane-enclosed
nucleus and various organelles that perform
specific functions
– Plants, animals, fungi, protists
• Prokaryotes: single-celled organisms lacking
organelles and a nucleus
– Bacteria and archaea
Activity:
• Go over reading assignment #1
• Testing your comprehension questions
#1-4
• Seeking Solutions questions #1 and 5
• Dead Zone Questions/Scenario
• HW: sec 2 reading assignment for
tomorrows discussion
Activity:
• After presenting Scenario 1 or 2, Work on
the following:
• Kinetic vs. Potential Energy
• Explain how Photosynthesis works
• Relate photosynthesis to Primary
Productivity
• Compare Photosynthesis to Cellular
Respiration
Energy fundamentals
• Energy: an intangible phenomenon that can
change the position, physical composition, or
temperature of matter
– Potential energy: energy of position
– Kinetic energy: energy of motion
– Chemical energy: potential energy held in the bonds
between atoms
• Potential energy is changed into kinetic energy
to produce motion, action, and heat.
Energy is conserved...but
changes in quality
• First law of thermodynamics: energy can
change forms, but cannot be created or
destroyed
• Second law of thermodynamics: the nature of
energy changes from a more-ordered to a lessordered state if no force counteracts this
tendency
– Entropy: an increasing state of disorder
– For example, burning a log of firewood transforms the
log from a highly organized product into light and heat
energy, gases, smoke, and carbon ash.
The sun’s energy powers life
• The energy that powers Earth’s ecological
systems originates mainly from the sun.
• The sun releases radiation from the
electromagnetic spectrum.
– Some is visible light
Photosynthesis
• Autotrophs (producers):
produce their own food from the
sun’s energy
– Green plants, algae, and
cyanobacteria
• Photosynthesis: the process of
turning light energy from the sun
into chemical energy
– Carbon dioxide + water + sun’s
energy is converted into sugars and
high-quality energy.
– Low-quality energy is turned into
high-quality energy.
Photosynthesis produces food
• Chloroplasts: organelles where
photosynthesis occurs
– Contain chlorophyll: a light-absorbing pigment
– Light reaction: solar energy is used to split water
to form oxygen and a small, high-energy
molecule that fuels the….
– Calvin cycle: links carbon atoms from carbon
dioxide into sugar (glucose)
6CO2 + 6H20 + the sun’s energy
C6H12O6 + 6O2
Cellular respiration releases
chemical energy
• Organisms can use chemical energy created by
photosynthesis through cellular respiration.
– Oxygen is used to convert glucose into water + carbon
dioxide + energy.
– Only 2/3 of the original energy input per glucose
molecule is gained in respiration.
– Occurs in autotrophs and organisms that feed on others
• Heterotrophs (consumers): organisms that gain
energy by feeding on others
– Animals, fungi, microbes
C6H12O6 + 6O2
6CO2 + 6H20 + energy
Energy and matter in
ecosystems
• Ecosystem: all organisms and
non-living entities occurring and
interacting in a particular area
–Animals, plants, water, soil, nutrients,
etc.
• Energy from the sun flows in one direction
through ecosystems.
• Energy is processed and transformed.
• Matter is recycled within ecosystems.
• Outputs: heat, water flow, and waste
Energy is converted to biomass
• Primary production: conversion of solar energy
to chemical energy by autotrophs
– Gross primary production: assimilation of energy by
autotrophs
– Net primary production (NPP): energy remaining
after respiration, used to generate biomass
• Available for heterotrophs
• Productivity: rate at which autotrophs convert
energy to biomass
Net primary productivity of
ecosystems
High net primary productivity: ecosystems whose plants
rapidly convert solar energy to biomass
A global map of NPP
NPP increases with temperature and precipitation on land, and
with light and nutrients in aquatic ecosystems.
Nutrients can limit productivity
• Nutrients: elements and compounds that
organisms consume and require for survival
– Stimulate plant production
– Lack of nutrients can limit production.
– Nitrogen and phosphorus are important for plant and
algal growth.
• Oceanic primary productivity is highest in water
near shore.
– Over 200 dead zones now exist due to nutrient
pollution.
Nutrient runoff devastates
aquatic systems
• Aquatic dead zones result from nutrient
pollution from farms, cities, and industry.
– Most dead zones are located near Europe
and the eastern U.S.
• Scientists are investigating innovative and
economical ways to reduce nutrient runoff.
Phytoplankton blooms off the
Louisiana coast.
Ecosystems: Different Sizes
• Ecosystems vary greatly in size.
• The term “ecosystem” is most often
applied to self-contained systems of
moderate geographic extent.
– Adjacent ecosystems may interact
extensively.
– Ecotones: transitional zones between
two ecosystems in which elements of
each ecosystem mix
Landscape ecology
• Landscape ecology: the study of how
landscape structure affects the abundance,
distribution, and interaction of organisms
– Helpful for sustainable regional development
– Useful for studying migrating birds, fish, mammals
• Patches: ecosystems, communities, or habitat
form the landscape and are distributed in
complex patterns (a mosaic)
This landscape consists of
a mosaic of patches of 5
ecosystems.
Conservation biology
• If a habitat is distributed in patches, organisms face
danger in traveling from one patch to another.
– Patches spaced too far apart prevent travel
• Conservation biologists: study the loss,
protection, and restoration of biodiversity
– Humans are dividing habitat into small, isolated patches.
– Corridors of habitat can link patches.
• Geographic information systems (GIS): computer
software that layers multiple types of satellite data to
create a complete picture of a landscape
– Geology, vegetation, animal species, and human
development
Activity:
• Testing Your Comprehension Questions
#5-7
• Calculating Ecological Footprints
• HW: Complete the “Testing Your
Comprehension” Questions, 8-10 after
reading pages 63-69; Biogeochemical
Cycles
Nutrients circulate through
ecosystems
• Physical matter is circulated continually in
an ecosystem.
• Nutrient (biogeochemical) cycle: the
movement of nutrients through
ecosystems
– Pools (reservoirs): where nutrients remain
for varying amounts of time
– Flux: movement of nutrients among pools
• Can change over time
Activity: 9/6/12
• Carbon Cycle- 2
• Phosphorus- 2
• Nitrogen- 3
– Nitrification
– Denitrificaiton
• Hydrologic- 2
• Sulfur- 2
• Create brochure, pamphlet, video, etc.
explaining each in detail (no less than 5
min, no more than 15)
– 1 day in class (tomorrow)
The carbon cycle
• Carbon cycle: describes the routes that carbon
atoms take through the environment
• Through photosynthesis, producers move carbon
from the air and water to organisms.
• Respiration returns carbon to the air and oceans.
• Decomposition returns carbon to the sediment, the
largest reservoir of carbon.
– Ultimately, it may be converted into fossil fuels.
• The world’s oceans are the second largest
reservoir.
– Obtain carbon from the air and organisms
The carbon cycle
Humans affect the carbon cycle
• Burning fossil fuels moves carbon from the
ground to the air.
• Cutting forests and burning fields moves
carbon from organisms to the air.
• Today’s atmospheric carbon dioxide reservoir
is the largest in the past 800,000 years.
– The driving force behind climate change
The phosphorus cycle
• Phosphorus cycle: describes the routes that
phosphorus atoms take through the
environment
– No significant atmospheric component
– Most phosphorus is within rocks and is released
by weathering.
• With naturally low environmental
concentrations, phosphorus is a limiting factor
for plant growth.
• Phosphorus is a key component of cell
membranes, DNA, RNA, and other
The phosphorus cycle
Humans affect the phosphorus
cycle
• Mining rocks for fertilizer moves phosphorus
from the soil to water systems.
• Wastewater discharge also releases
phosphorus, which boosts algal growth and
causes eutrophication.
• May be present in detergents
– Consumers should purchase phosphate-free
detergents.
The nitrogen cycle
• Nitrogen comprises 78% of our atmosphere and is
contained in proteins, DNA, and RNA.
• Nitrogen cycle: describes the routes that
nitrogen atoms take through the environment
– Nitrogen gas is inert and cannot be used by organisms.
– Needs lightning, bacteria, or human intervention
• Nitrogen fixation: Nitrogen gas is combined
(fixed) with hydrogen by nitrogen-fixing bacteria or
lightning to become ammonium
– Can be used by plants
– Nitrogen-fixing bacteria live in legumes (i.e., soybeans)
Nitrification and denitrification
• Nitrification: bacteria that convert
ammonium ions first into nitrite ions then into
nitrate ions
– Plants can take up these ions
• Animals obtain nitrogen by eating plants or
other animals.
• Denitrifying bacteria: convert nitrates in soil
or water to gaseous nitrogen, releasing it
back into the atmosphere
The nitrogen cycle
Humans affect nitrogen cycle
• Excess nitrogen leads to hypoxia in coastal areas.
• Synthetic fertilizers doubled the rate of Earth’s nitrogen
fixation.
• Burning forests and fossil fuels leads to acid precipitation.
• Wetland destruction and increased planting of legumes
has increased nitrogen-rich compounds on land and in
water.
• Increased emissions of nitrogen-containing greenhouse
gases
• Calcium and potassium in soil are washed out by
fertilizers.
• Reduced biodiversity of plants adapted to low-nitrogen
soils.
• Changed estuaries and coastal ecosystems and fisheries
Human inputs of nitrogen into
the environment
Fully half of nitrogen entering the environment is of human origin.
A law addressing hypoxia in the
Gulf
• The Harmful Algal Bloom and Hypoxia Research
and Control Act (1998) called for an assessment of
hypoxia in the Gulf and to:
–
–
–
–
–
–
–
Reduce nitrogen fertilizer use in Midwestern farms
Change timing of fertilizer applications to minimize runoff
Use alternative crops
Manage livestock manure
Restore wetlands and create artificial ones
Improve sewage-treatment technologies
Evaluate these approaches
• This Act has worked, and was reauthorized in 2003.
The hydrologic cycle
• Water is essential for biochemical reactions and is involved
in nearly every environmental system.
• Hydrologic cycle: summarizes how liquid, gaseous, and
solid water flows through the environment
– Oceans are the main reservoir.
– Less than 1% is available as fresh water.
• Evaporation: water moves from aquatic and land systems to
air
• Transpiration: release of water vapor by plants
• Precipitation: condensation of water vapor as rain or snow
returns water from the air to Earth’s surface
Groundwater
– Aquifers: underground reservoirs of spongelike
regions of rock and soil that hold …
– Groundwater: water found underground beneath
layers of soil
– Water table: the upper limit of groundwater held
in an aquifer
– Water may be ancient (thousands of years old).
The hydrologic cycle
Human impacts on hydrologic
cycle
• Damming rivers increases evaporation and infiltration into
aquifers.
• Altering the surface and vegetation increases runoff and
erosion.
• Spreading water on agricultural fields depletes rivers, lakes,
and streams and increases evaporation.
• Overdrawing groundwater for drinking, irrigation, and
industrial uses depletes groundwater resources.
• Removing forests and vegetation reduces transpiration and
lowers water tables.
• Emitting pollutants changes the nature of precipitation.
Sulfur
• Occurs in Atmosphere
• Hydrogen Sulfide (H2S) + (Sulfur Dioxide) SO2
naturally (volcanoes), manmade (industry)
• H2S + O2 --- SO2
• SO2 + O2 -- SO3 (sulfur tri-oxide) or
• SO2 + H2O - H2SO4 (sulfuric acid) - acid
deposits, water and soils, plants and animals
Conclusion
• Life interacts with its abiotic environment in
ecosystems through which energy flows and
materials are recycled.
• Understanding biogeochemical cycles is crucial.
– Humans are causing significant changes in the ways
those cycles function.
• Understanding energy, energy flow, and
chemistry increases our understanding of
organisms, their environment, and how
environmental systems function.
• Thinking in terms of systems can teach us how
to avoid disrupting Earth’s processes and how to
mitigate any disruptions we cause.
QUESTION: Review
Which of the following part of an atom
has a positive charge?
a)
b)
c)
d)
e)
Proton
Neutron
Electron
Hydrogen
Neutreno
QUESTION: Review
Which of the following consists of a
chemically diverse group of compounds
that don’t dissolve in water?
a)
b)
c)
d)
e)
Nucleic acids
Proteins
Carbohydrates
Lipids
Polymers
QUESTION: Review
Sugars, starches, and glucose are all:
a)
b)
c)
d)
e)
Lipids
Proteins
Carbohydrates
Nucleic acids
Synthetic molecules
QUESTION: Review
According to the first law of thermodynamics:
a) Energy cannot be created or destroyed
b) Things tend to move toward a more disorderly
state
c) Matter can be created, but not energy
d) Kinetic energy is the most efficient source of
energy
e) Energy is constantly recycled
QUESTION: Review
Which of the following organisms is an
autotroph?
a)
b)
c)
d)
e)
Deep-sea tubeworm
Horse
Pine tree
Human
None of these
QUESTION: Review
A transitional zone between two ecosystems
is a(n):
a)
b)
c)
d)
e)
Conservation zone
Corridor
Reservoir
Ecotone
Patch
QUESTION: Review
Humans have affected the nitrogen cycle
in all of the following ways EXCEPT:
a) Doubling the rate of nitrogen fixation
b) Increasing emissions of greenhouse
gases
c) Lowering water tables
d) Changing estuaries and coastal
ecosystems
e) Reducing diversity of plants adapted to
nitrogen-poor soils
QUESTION: Weighing the
Issues
Who should be responsible for reducing
nitrogen pollution and eutrophication off
coastal waters?
a)
Fishermen, since they reap the benefits of fishing
b) Farmers, since they are causing much of the problem
c) Taxpayers, since they are getting both fish and food
d) The federal government, since it’s job is to protect
American citizens and the environment
QUESTION: Interpreting
Graphs and Data
A molecule of the hydrocarbon ethane contains:
a) 10 carbon atoms and 8
hydrogen atoms
b) 8 carbon molecules and 10
hydrogen enzymes
c) 2 carbon atoms and 6
hydrogen atoms
d) 2 different ions
QUESTION: Interpreting
Graphs and Data
Which is the most
basic material?
a)
b)
c)
d)
e)
Lemon juice
Acid rain
Rainwater
Seawater
Soft soap
QUESTION: Interpreting
Graphs and Data
According to this graph,
which ecosystem has the
lowest amount of
biomass?
a) Temperate
grassland
b) Boreal forest
c) Savanna
d) Tropical
rainforest