Introduction to Environmental
Science
Chapters 1 and 2
We Cannot Create or Destroy Matter
• Law of conservation of
matter – matter cannot
be created nor
destroyed
• Matter is converted from one
form to another
Everything we think we have thrown away remains here with us in some form…
Energy Changes Are Governed by Two
Scientific Laws
• First Law of Thermodynamics
– Energy input always equals energy output
• Second Law of Thermodynamics
– Energy always goes from a more useful to a less
useful form when it changes from one form to
another
• Decreased energy efficiency
The Second Law of Thermodynamics
in Living Systems
Systems Respond to Change through
Feedback Loops
• Positive feedback loop
- causes a system to
change in the same
direction
Systems Respond to Change through
Feedback Loops
• Negative feedback loop
– causes a system to
change in the opposite
direction from which it
is moving
– Opposing process
• Can promote
sustainability!
– Aluminum mining  can
 recycling
Time Delays Can Allow a System to
Reach a Tipping Point
• Time delays vary
– Between the input of a
feedback stimulus and
the response to it
– Example: Planting trees
• Tipping point, threshold
level
– Causes a shift in the
behavior of a system
System Effects Can Be Amplified
through Synergy
• Synergistic interaction – two or more
processes interact so that the combined effect
is greater than the sum of their separate
effects
– Helpful
• E.g., campaign vs. individual persuasion
– Harmful
• E.g., Smoking and inhaling asbestos particles
Ecology
Chapters 3 and 4
Habitat vs. Niche
• Habitat – place where an organism lives
– Organisms address
• Niche – role of an organism in an ecosystem
(physical, chemical, and biological conditions
that a species needs to live and reproduce)
– Organisms occupation
• Thousands of organisms can occupy the same
habitat but each organism has its own niche.
Habitat vs. Niche
Levels of Organization of Life
•
Organism- a living thing
•
Population- a group of
organisms of the same species
that live in a particular area
•
Community- populations of
different species that live in one
particular area
Several Abiotic Factors Can Limit
Population Growth
• Limiting factor principle
– Too much or too little of any abiotic factor can
limit or prevent growth of a population, even if
all other factors are at or near the optimal range
of tolerance
Range of Tolerance for a Population
of Organisms
• Range of tolerance may vary in populations
– Small differences in genetic makeup, health, and age
A Food Chain
Ecological Efficiency
• No organism EVER receives
all of the energy from the
organism it just ate
• 10% Law
– Only 10% of the energy from
one trophic level is
transferred to the next
Some Ecosystems Produce Plant
Matter Faster Than Others Do
• Gross primary productivity (GPP)
– Rate at which an ecosystem’s producers convert
solar energy into chemical energy stored in their
tissues
• Net primary productivity (NPP)
– Rate they create and store energy minus the
energy they use for homeostasis
– Ecosystems and life zones differ in their NPP
Nutrients Cycle in the Biosphere
• Biogeochemical cycles, nutrient cycles
– Nitrogen
– Hydrologic
– Carbon
– Phosphorus
– Sulfur
• Connect past, present, and future forms of life
Nitrogen Fixation
• Nitrogen gas cannot be
used by living things
directly
– Converted by lightening
• Bacteria in soil and
ocean convert nitrogen
gas into ammonium
(NH4+) and nitrates
(NO3-)
– Fixation
Assimilation
• Used by plants to
produce amino acids,
proteins, nucleic acids,
and vitamins
• When organism dies
bacteria convert
proteins into ammonia
or ammonium
– Ammonification
Returning Nitrogen
• Specialized bacteria in soil and bottom of lakes
convert NH3 and NH4+ back into nitrates
– Nitrification
• Nitrates are converted to nitrogen gas and
returned to the atmosphere
– Denitrification
– N2
– N2O
Nitrogen Cycle Summary
• Fixation
– gas  ammonium or nitrate
• Assimilation
– Taken up by plants through roots; incorporated into proteins
• Ammonification
– Bacteria break down proteins into ammonia and ammonium
• Nitrification
– Ammonia  nitrates
• Denitrification
– nitrates  gas
Human intervention in the nitrogen
cycle
– Additional NO and N2O
• Burning fuels at high
temperatures
– Destruction of forest,
grasslands, and wetlands
– Add excess nitrates to
bodies of water
• Runoff
– Remove nitrogen from
topsoil
• Harvesting nitrogen rich
crops and irrigation
Nitrogen Cycle in a Terrestrial Ecosystem with
Major Harmful Human Impacts
Hydrologic Cycle Including Harmful Impacts of
Human Activities
Alteration of the hydrologic cycle by
humans
• Withdrawal of large
amounts of freshwater
at rates faster than
nature can replace it
• Clearing vegetation
– Increases temperature
and thus evaporation
• Increased flooding
when wetlands are
drained
Carbon Cycle Equations
Cellular Respiration
C6H12O6 + 6O2  6CO2 + 6H2O +ATP
Photosynthesis
6CO2 + 6H2O sunlight C6H12O6 + 6O2
Carbon Cycle
• Marine sediments are
earth’s largest store of
carbon
– Carbon is trapped
between layers of
sediment
– Converted to fossil fuels
when heated and
compressed
Natural Capital: Carbon Cycle with Major Harmful
Impacts of Human Activities
Phosphorous Cycle
• Phosphorus
– Helps form important molecules like DNA, RNA,
and ATP
 Inorganic phosphate PO43- is released into the
soil and water as sediments wear down.
– Eventually enters the ocean, where it is used by
marine organisms
– Does NOT include the atmosphere
Phosphate Cycle
• Organic phosphate
moves through the
food web and to the
rest of the ecosystem.
Organisms
Land
Ocean
Sediments
Phosphorus Cycle with Major Harmful
Human Impacts
Sulfur Cycles through the Biosphere
• Sulfur found in organisms, ocean sediments,
soil, rocks, and fossil fuels
• SO2 in the atmosphere
• H2SO4 and SO4- released during volcanic
eruptions (toxic)
Sulfur Cycles through the Biosphere
• Human activities affect the sulfur cycle
– Burn sulfur-containing coal and oil
– Refine sulfur-containing petroleum to make
gasoline and other heating products
– Convert sulfur-containing metallic mineral ores
• Copper lead and zinc
Natural Capital: Sulfur Cycle with Major Harmful
Impacts of Human Activities
Evolution
Chapter 5
Individuals in Populations with Beneficial Genetic
Traits Can Leave More Offspring
• When environmental conditions change,
populations
– Adapt
– Migrate
– Become extinct
• Genetic resistance – ability of one or more
organisms in a population to tolerate a chemical
designed to kill it
• Malaria
A group of bacteria,
including genetically
resistant ones, are
exposed to an
antibiotic
Normal
bacterium
Most of the normal
bacteria die
Resistant
bacterium
The genetically
resistant bacteria
start multiplying
Eventually the
resistant strain
replaces the strain
affected by
the antibiotic
Geologic Processes Affect Natural
Selection
• Tectonic plates affect evolution and the
location of life on earth
– Location of continents and oceans
– Species physically move, or adapt, or form new
species through natural selection
• Earthquakes
• Volcanic eruptions
Geographic Isolation Can Lead to
Reproductive Isolation
Extinction is Forever
• Extinction
• Endemic species
– Species found only in
one area
– Particularly vulnerable
– Golden Toad (Costa
Rica) died out when
habitat dried up
Species Diversity: Variety, Abundance of
Species in a Particular Place
• Species diversity
– Species richness –
number of different
species in a community
– Species evenness –
abundance of organisms
within each type of
species
Species Diversity: Variety, Abundance of
Species in a Particular Place
• Most species-rich
communities
–
–
–
–
Tropical rain forests
Coral reefs
Ocean bottom zone
Large tropical lakes
Worldwide Richness?
• Diversity varies with geographical location
– Richness is highest at tropics
– Lowest at the poles
Each Species Plays a Unique Role
in Its Ecosystem
• Generalist species
– Broad niche
– Live in different places, eat
different food, high range
of tolerance
– Examples?
• Specialist species
– Narrow niche
– More prone to extinction
– Examples?
Specialist Species and Generalist
Species Niches
Niches Can Be Occupied by Native
and Nonnative Species
• Native species –
organisms that normally
live and thrive in a
particular ecosystem
• Nonnative species invasive, alien, or exotic
species
– May spread rapidly
– Not all are villains
Indicator Species Serve as Biological
Smoke Alarms
• Indicator species – species that provide
early warnings of damage to a community or
ecosystem
– Can monitor environmental quality
•
•
•
•
Trout
Birds
Butterflies
Frogs
Coal Canaries: 1800s – 1900s
• Coal miners took caged
canaries into mines to
act as early warning
sentinels
• If birds stopped singing
and appeared to be
distressed miners knew
there were poisons
being released
Keystone, Foundation Species Determine
Structure, Function of Their Ecosystems
• Keystone species – have a large effect on the
types and abundances of other species in an
ecosystem
– Pollinators
– Top predator
• Foundation species
– Create or enhance their habitats, which benefit others
• Elephants
• Beavers
Endangered Species
Chapter 9
Endangered and Threatened Species Are
Ecological Smoke Alarms
• Endangered species
– so few individual
survivors that species
could soon become
extinct over its range
• Threatened speciesstill abundant, but
numbers are declining
Loss of Habitat Is the Single Greatest Threat
to Species: Remember HIPPCO
H
I
P
P
C
O
• Habitat destruction, degradation, and fragmentation
• Invasive (nonnative) species
• Population and resource use growth
• Pollution
• Climate change
• Overexploitation
Ecological Succession
• Natural ecological restoration
– Primary succession – gradual establishment
of biotic communities in lifeless areas where
there is no soil or sediment
– Secondary succession – series of
communities with different species develop in
places containing only soil or bottom sediment
No Population Can Grow Indefinitely:
J-Curves and S-Curves
• Biotic potential –
capacity for
population growth
under ideal
conditions
– Larger organisms
tend to have low
potential
Population Growth
• Exponential growth – population that
increases at a fixed rate
– J-Curve
• Logistic growth – rapid exponential
population growth followed by a steady
decrease in population growth
– S-Curve
Population Growth
S-Curves
• Environmental resistance –
combination of all factors that act to limit
the growth of a population
• Carrying capacity (K) – maximum
population of a given species that a
habitat can sustain indefinitely without
being degraded
S-Curves
Phases of Logistic Growth Curve
1. Lag Phase – little initial growth.
2. Rapid Growth Phase
3. Stable Phase – stabilizing factors limit growth
Species Reproductive Patterns
• r-Selected species, opportunists – species with a
capacity for a high rate of population increase
– Many small offspring
– Little to no parental care or protection
– Reproductive opportunists
• K-selected species, competitors – reproduce
later in life and have a small number of offspring
with fairly long life spans
– Few large offspring
– High parental care
Positions of r- and K-Selected Species on the SShaped Population Growth Curve
Top-down Regulation
Chapter 10
Forestry
Forests Vary in Their Make-Up,
Age, and Origins
• Old-growth or
primary forest –
uncut or regenerated
primary forest that
has been undisturbed
for 200 years or more
– 36% of world’s forests
– ¾ found in Russia,
Canada, Brazil,
Indonesia and Papua
New Guinea
Forests Vary in Their Make-Up,
Age, and Origins
• Second-growth
forest – result from
secondary ecological
succession; develop
after forest
destruction
– 60% of world’s forests
Rotation Cycle of Cutting and
Regrowth of a Monoculture Tree
Plantation
Fire, Insects, and Climate Change Can
Threaten Forest Ecosystems
• Surface fires
– Usually burn leaf litter
and undergrowth
• Kill seedlings and small
trees
• Spare most mature
trees; allow wildlife to
escape
– Stimulate seed
germination
• Sequoia and jack pine
– Burn away flammable
ground material
• Prevents more
destructive fires
Fire, Insects, and Climate Change Can Threaten
Forest Ecosystems
• Crown fires
– Extremely hot: burns
whole trees
– Kill wildlife
– Increase soil erosion
– Occur in forests that
have not experienced
surface fires for
several decades
Unsustainable Logging is a Major
Threat to Forest Ecosystems
• Increased erosion
– Sediment runoff into
waterways
• Habitat fragmentation
– Loss of biodiversity
• Invasion by
– Nonnative pests
– Disease
– Wildlife species
Natural Capital Degradation: Building Roads
into Previously Inaccessible Forests
Unsustainable Logging is a Major
Threat to Forest Ecosystems
• Major tree harvesting
methods:
– Selective cutting
– Clear-cutting
– Strip cutting
We Can Improve the Management
of Forest Fires
• The Smokey Bear
educational campaign
– Forest Service and
National Advertising
Council
– Convinced public that
ALL forest fires are
bad
• Increases the likelihood
of crown fires
• Threaten 40% of
federal forest lands
from fuel buildup and
slash (logging debris)
We Can Improve the Management
of Forest Fires
• Prescribed fires –
careful planning
• Herds of goats to eat
underbrush (CA)
• Allow fires on public
lands to burn
Degradation of Tropical Forest:
Positive Feedback Loop
• Step 1: Roads
– Cut deep into a forest for logging and settlement
– Selective cutting; large trees fall but bring small
trees with them because of vines and canopy
• Step 2: Ranchers buy land
– Cattle ranchers use land for grazing
– After overgrazing herds move
• Step 3: Settlers buy land for harvesting
– Grow food to survive
– Soil nutrients depleted after a few years and
land is barren
Grasslands
• Rangelands –
unfenced grasslands
in temperate and
tropical climates that
supply forage
(vegetation) for
grazing (grass-eating)
and browsing (shrubeating) animals
Grasslands
• Pastures – managed
grasslands or
enclosed meadows
usually planted with
domesticated grasses
or other forage
Important ecological services of
grasslands
•
•
•
•
Soil formation
Erosion control
Nutrient cycling
Storage of
atmospheric carbon
dioxide in biomass
• Maintenance of
diversity
Riparian Zones
• Thin strips of lush
vegetation along
streams or rivers
– Livestock tend to
aggregate around
natural water sources
Natural Capital Degradation: Overgrazed and
Lightly Grazed Rangeland
Restoration of Grazing Lands
Case Study: Stresses on U.S.
Public Parks
• 58 Major national parks in the U.S.
• Biggest problem may be popularity
–
–
–
–
Noise
Congestion
Pollution
Damage or destruction to vegetation and wildlife
• Repairs needed to trails and buildings
Natural Capital Degradation:
Damage From Off-Road Vehicles
Endangered Natural Capital:
Biodiversity Hotspots in the U.S.