The nutrient cycles you should be thoroughly familiar with
are:
You may also see the phosphorus cycle show up
on the AP test. This is the simplest cycle. Most
• Carbon,
• Hydrologic, and of the phosphorus found in the phosphorus cycle
originates in the rocks beneath your feet. (if a cycle
• Nitrogen.
has an origin).
The hydrologic cycle helps the
phosphorus cycle out, by eroding the
rocks, and releasing the phosphorus
into the soil, and water.
It is taken up by plants and animals, and
then when they die, it is added back to
the soil, where it has the potential to
be made into rocks again!
The carbon and hydrologic cycles are also
quite easy. Remember the following:
Hydrologic cycle Processes:
• Evaporation: liquid to a gas
• Condensation: gas to a liquid (clouds)
• Precipitation: liquid or solid to the ground
• Runoff: over the ground
• Infiltration: Into the ground
• Transpiration: Plants participating in the cycle as
water vapor moves through the stomata of a plant.
Carbon cycle Processes:
• Photosynthesis: Plants manufacture glucose, and
take CO2 in, Oxygen out
• Respiration: Both cellular, and breathing…it is the
exchange of gases O2 for CO2. (opposite of
photosynthesis) Process breaks down glucose to
produce ATP
• Decomposition releases CO2 back to atmosphere Carbon is also found in our fossil fuels, and
• Largest Carbon sink: Ocean (dissolved CO2) and when we burn them (combustion), we add
the original carbon from the organisms that
shelled organisms (CaCO3)
fossilized, back into the atmosphere.
Of all the nutrient cycles, the Nitrogen Cycle is the most difficult to
understand, because of all the different stages.
Stages of the Nitrogen Cycle to Remember:
Nitrogen Fixation: Soil bacteria convert N2
(atmospheric nitrogen) into ammonia (NH3)
• Nitrification: Nitrifying bacteria convert
the ammonia into nitrate.
• Assimilation: Nitrate is assimilated and
absorbed by plants (which are consumed by
animals to pass the nitrogen on in the food
web) This nitrogen in plants is used to help
make amino acids, the building blocks of
proteins.
• Ammonification: After death,
ammonifying bacteria break nitrogen
compounds in the body down, and return
them back to the soil in the form of
ammonia.
• Denitrification: Denitrifying bacteria can
take nitrates and convert them into
atmospheric nitrogen again, completing the
cycle.
The topic of energy is so broad that we will try to narrow it down into a couple
of different energy-related topics. Here’s what we’re going to review in the
energy unit:
• Laws of Thermodynamics
• Energy Flow in Ecosystems
• Fossil Fuels
•Renewable Energy Sources
•Nuclear Energy
The First Law is that heat energy cannot be created or destroyed. (This is also
known as the law of conservation of energy.) Heat can only flow from place to
place, or change form.
The Second Law says that entropy (disorder) always increases in a closed
system. (A closed system is one that does not exchange any energy with the
surrounding environment.) This means that everything in the universe is tending
toward falling apart, slowing down, and becoming more disorganized.
Biological systems can use energy from the sun as it flows through ecosystems.
Energy can be stored in these systems (for instance, in chemical bonds) for a
time, and then released again and dissipated into the environment. The Laws of
Thermodynamics help to explain all of that movement.
Since this is one of the most understood of concepts, let’s do a quick
review. Remember:
The 10% rule: Only 10% of the available energy at each trophic level is
transferred to the next level. An ecological pyramid illustrates the 10%
rule. So, if there is 8,596 units available at the producer level, the
primary consumers incorporate only 859.6 units, secondary…85.96 etc...
It is for that reason that a pyramid
of numbers would appear like this:
And a pyramid of
biomass would look
like this:
Energy flows from the
original source, the
sun, to the
producers. From
there, to each of the
consumers, and finally
to the decomposers.
There is a history of fossil fuel use by humans that goes back about
35,000 years bp. Burned coal shards found in a Neanderthal fire pit
show that even our distant relatives knew of the usefulness of coal.
There are three types of fossil
fuels, each of which formed in
different ways, 300 to 400 million
years ago.
• Coal: formed from fossil remains
of tree ferns that grew in swampy
areas during the Carboniferous
Period
• Oil: formed from the
fossilized remains of sea
creatures, zooplankton and
phytoplankton during that
same period.
• Natural Gas: formed from
similar organisms as oil, and
usually found in association
with an oil reservoir.
About 86% of the world’s commercial
energy is supplied by fossil fuels.
From least to most efficient:
Coal: Most plentiful, and cheapest…
The less efficient forms
but least environmentally friendly.
produce more sulfur when
• Peat (compressed plant material)
burned. This adds SO2 to the
• Lignite (sedimentary, with some fibers)
atmosphere, which in turn
• Bituminous (sedimentary)
can produce sulfuric acid rain
• Anthracite (Metamorphic)
when combined with H2O
Crude Petroleum (Oil): Most used fossil fuel
• Can be separated through refinement into gasoline, heating oil, even
asphalt.
• Is hard to recover, and requires special techniques after the natural
pressure is exhausted from a well.
• Secondary recovery typically only produces up to 30-40% total in any
reservoir.
Natural Gas (Made of mostly methane…CH4)
• Cleanest burning fossil fuel…and the most wasted
Types of Resources:
• Inexhaustible (like the sun’s energy)
• Renewable (like wind, water, and biomass)
• Nonrenewable (like fossil fuels, metals, and minerals)
For the Human Population to move toward sustainability, we must move
toward less reliance on fossil fuels.
What are the Answers?
• Synfuels: synthetic fuel is a
liquid fuel obtained from coal or
natural gas. Coal can be
converted to synthetic natural gas
by coal gasification, or methanol,
through a process called coal
liquefaction. While using synfuels
reduces particulates, it increases
CO2 emissions, and there are only
moderate energy yields.
Relies on the potential energy created by the dam. When the water is allowed
to flow through penstocks, a turbine spins, which generates electricity.
The dam does produce cheap electricity, but
the negative environmental effects include:
• significant alteration of landscape and
destruction of habitats due to reservoir
• increased evaporation due to reservoir,
especially in warm environments
• Floods upstream
• Disruption of migrating and spawning fish
• Build-up of sediments near dam
Relies on the energy from the sun, and the
technology of the parabolic trough, or solar panels.
• Passive: no moving parts, such as using the sun’s
energy to dry your clothes on the line.
• Active: use pumps to move heated liquids
through a small collector.
Problems occur when the sun doesn’t shine. Hybrid technologies which use
natural gas during those times work well in those circumstances.
Wind energy is actually a by-product of solar energy…as the sun’s energy
drives weather patterns on Earth.
It is created from the unequal heating of Earth’s surface by the sun,
and the rotation of the Earth on its axis.
While most popular in Europe, it is growing
more popular in the US as farmers lease
their land for wind power.
• No CO2 emissions
• Land beneath turbine can still be used for
farming and grazing
• Easily and quickly constructed
• Rely on good strong winds
• Visual and noise pollution
• Danger to migrating birds
Both tides, and waves may be captured to generate energy.
Technology relies on trapping moving water, and then releasing it through a
penstock, turning a turbine (similar to other hydroelectric technology)
Roughly translates as “Earth-Heat”, this is one of the only energy resources that
does NOT rely on the sun’s energy!
When the heat energy stored in the Earth’s Mantle is harnessed, and used to
heat fluids which in turn move through turbines, which generate electricity, we
are using one of the cleanest forms of alternative energy.
Yellowstone National Park:
The largest geothermal region in the US
Iceland, Japan and New Zealand:
The largest geothermal regions in the
world.
• Long life-time of use
• Little waste is eliminated
• no mining or transportation costs
• Relatively scarce resources
• Some CO2 emissions
Energy efficiency is the measure of the useful energy produced compared to the energy
that is consumed. For instance, the light produced by a light bulb is useful. The heat is
wasted. An incandescent bulb is only 5% efficient, while a fluorescent bulb is 22%
efficient.
Fuel efficiency for cars rose
In 1975, Congress enacted the Energy Conservation markedly between 1973 and 1985
Act. The Corporate Average Fuel Economy (CAFÉ) because of this act.
standards were added to this act as an amendment.
The two types of Nuclear Energy are:
Fusion, and Fission
Fusion:
Example…the energy from the sun
Fuel is very small nuclear elements, such as hydrogen,
which fuse together to form helium
Not yet perfected on Earth, because of the extreme
temperatures needed for the reaction.
Temperatures on the sun where the reaction does occur
naturally exceed 15 million degrees C. We have had
limited success on Earth recreating the energy, but it
costs more to produce that the resulting energy
generated!
Some important incidents in
Earth History include two
notable nuclear disasters.
Fission:
Uses a fuel of very large radioactive elements, such as
Chernobyl: Ukraine, used
Uranium and Plutonium, and forces them to split apart in a graphite to enclose the core. A
nuclear reaction. When this occurs in a controlled manner, fire in the core enabled nuclear
heat is also released. The heat is used to heat water to formfuels to escape and cause
steam, which is used to turn a turbine, which generates
environmental devastation.
electricity.
Three-Mile Island: near
Problems include the toxicity of the waste, which is at
Harrisburg, Pa. Resulted in a
present stored in large steel drums and buried in landfills.
partial core melt-down, releasing
Benefits include relatively cheap energy, with low emissions. radioactive gases
It is a far cleaner alternative to fossil fuels.
Biodiversity, or biological diversity is one of the most important natural
resources on Earth. It supplies food, wood, fibers, energy, medicine, and more.
It also helps to maintain the quality of our air, water, and soils, as well as
controls pests. There are four types:
The variety of genetic material within a species or a
population
The number of species in different habitats
The variety of terrestrial and aquatic ecosystems
The variety of biological and chemical processes
needed for the survival of ecosystems
Human threats to biodiversity can be summarized by the acronym HIPPO.
Habitat destruction, Invasive species, Pollution, Population, and
Overharvesting.
Why is preserving biodiversity so important? The greater the biodiversity, the more a
species is able to adapt and evolve to new environments that are occurring.
Invasive Species in the US:
• Kudzu vine, purple loosestrife, gypsy moth,
mongoose, sea lamprey, zebra mussel, and nutria.
These organisms outcompete the natives, because
they have no natural predators.
Perhaps the best known way that humans have attempted to preserve
biodiversity was the establishment of the Environmental Protection
Agency, by President Nixon in 1970. Its function is to protect human
health as well as protect and preserve Earth’s air, water, land, and
endangered species.
While many states had enacted hunting and fishing restrictions to preserve the
wildlife for future human use, it wasn’t until the enactment of the Endangered
Species Act in 1973, that legislation attempted to protect wildlife regardless of
how useful the species was to humans. (removed a certain anthropocentrism).
However, remember that species considered “pests” to humans still cannot be
added to any list.
To be “endangered”, a species must be in imminent danger of extinction.
To be “threatened”, a species must be in imminent danger of becoming
endangered.
A “vulnerable” species is any naturally rare species, or one that has been
depleted by humans and is unable to recover without human intervention.
Refers to a conflict between individual interests and the common good with
regard to the use of resources. In 1968, Garret Hardin argued in an infamous
article with this title that any commonly held resource would eventually and
inevitably be degraded or destroyed as people’s self-interest outweighed the
interests of the general public.
In most cases, humans will put the good of
themselves, or their families, over the good
of the community.
Many communal resources have been successfully managed and maintained:
Native American
management of hunting
grounds;
Switzerland
management of
pastureland and
forests;
Maine lobster fisheries
What do these all have in common?
• community members’ long history on the land or near
the resource anticipating this history to continue
• clearly defined resource
•Known community size
• resource is relatively scarce, and community must
work together to preserve it
• clear monitoring of resource depletion
• conflict resolution in place
• incentives to encourage compliance
•Clear consequences for abuse of resource
In the 1850’s, he published his ideas on how organisms can
change through time, in a book entitled The Origin of
Species. Regard the following points on Natural Selection:
• Similar organism reproduce similar organisms. A dog
reproduces a dog, and a dandelion reproduces a dandelion.
• Often, the number of offspring is overproduced: The number
that survive is less than that initially reproduced.
• Individual organisms must compete with each other and with
other species for limited resources in the environment (food,
water, space…etc)
• In any population, individuals vary with respect to any given
trait (height, skin color patterns, size, shape of beak)
• Some variations are favorable (make those individuals more
likely to be successful at reproduction, than those with
unfavorable traits)
• Those organisms with favorable traits will survive and pass
those traits on to their offspring. Those with unfavorable
traits will die and not pass on their traits (NATURAL
SELECTION)
• Given sufficient time, because natural selection will
accumulate these favorable traits, the species will change or
evolve.
The Earth is a layered, continually moving system. At the boundaries where
tectonic plates meet, earthquakes and volcanic eruptions occur, as well as the
creation of mountains and deep ocean trenches.
Earth’s climate is influenced by
atmospheric circulation as well as
the interaction of the atmosphere
and the ocean waters.
Water is a vital resource in Earth
that is needed for life.
Soil is a renewable resource that is
formed from weathered rock and
decaying organic material, as well as
living organisms.
Soil and water are both resources
that must be protected because
they are susceptible to degradation
and pollution. Agriculture depends
on these resources but can also
harm them.
The Geologic Time Scale divides Earth’s history of 4.6 billion years into
subgroups that are more manageable, arranging geologic events in an orderly
manner.
Eons represent the greatest length of time.
There have been four eons.
• Hadean: No rocks have survived from this eon,
which is the oldest. Earth was barren, with no
atmosphere.
• Archaen: The earliest rocks found on Earth date
from this time. The first life on Earth was appearing
about 3.8 billion years ago. It was prokaryotic
(bacterial) in nature.
• Proterozoic: Prokaryotic life abounded during
this eon, however, the end of this time includes the
Cambrian Explosion…a time of great diversification of
life, including complex multicellular life.
• Phanerozoic: We now live in the Phanerozoic era.
Organisms from this eon mainly represent the fossil
record.
The Paleozoic Era, during the Phanerozoic was
important for life’s diversification. By the end
of the Era, all forms of life had evolved…even
mammals. Also, this is the time when the
organisms that became our fossil fuels were
living.
The end of the Paleozoic Era marked a time on Earth when the largest mass
extinction occurred. There are many hypotheses about what may have
happened, including shield volcanoes, and gamma ray bursts from neighboring
super-novas.
The Mesozoic Era was known as the
age of Dinosaurs, and marked a
period in our geologic history when
reptiles ruled the Earth. The K-T
extinction event is responsible for
the destruction of these great
creatures, and made possible the
complex evolution of mammalian life.
The Cenozoic Era is known as the
age of Mammals, as mammalian life
dominates the planet.
Most Earth time periods are not
divided randomly. They coincide Earth’s tectonic plants have driven the
with extinction events in our
continents since their formation early in
Earth’s childhood.
geologic history.
There are three types of boundaries.
• Transform Transform boundaries are where tectonic
plates slide past one another. They form transform fault
boundaries. These are the great Earth Quake zones. Many
times the two plates slide gradually and smoothly along, but
sometimes the rocks along the faults will get stuck. Sudden
friction and movement cause Earthquakes. This is the great
San Andreas Fault, which divides the North American and
Pacific Plates. San Francisco is on the North American Plate,
while Los Angeles is on the Pacific. In our distant future, LA
will be a metroplex with San Francisco, as the Pacific Plate is
moving slowly northward.
•Convergent A convergent boundary is where two plates
move toward each other. Depending upon where they form,
they may be subduction zones, where portions of the boundary
move below a less dense region. Many times, volcanic mountains
form along these zones. When the convergent boundary occurs
along continental areas, such as the area north of the Indian
Plate, great mountains, such as the majestic Himalayas form
from that converging pressure. When two divergent boundaries
form along oceanic crust, a deep ocean trench forms, such as
the Marianas Trench in the Pacific Ring of Fire.
• Divergent Form where two plates move apart. Sea floor
spreading occurs in these areas, such as the Mid-Atlantic
ocean ridge, which is the longest mountain chain on Earth.
When earthquakes occur on or near the ocean floor, the result could
be a tsunami. Tsunami are giant seismic sea waves, often called “tidal
waves”, but they are entirely unrelated to tides.
Earthquakes and volcanoes can
affect the environment, and
economy of places where they
occur.
Where population density
is high, and overcrowding
exists, earthquakes and
volcanoes can alter the
environment to such a
degree that it can cause
serious threats to human
life.
While volcanoes are geologically “constructive” events, in
terms of human life, and indeed other organisms, they can
be destructive also.
The seasons on Earth are the result of interaction between Earth and
the Sun. The Earth is tilted to an angle of 23 ½ ˚ This influences the
altitude of the Sun’s rays over parts of the Earth. The direct rays of
the sun do not travel north, or south of 23 ½˚ as a result.
The day that this occurs in the
Northern Hemisphere is known as the
Summer Solstice (on or about June 21)
The day that this occurs in the
Southern Hemisphere is known as the
Winter Solstice (on or about December
21)
When the sun’s rays are directly over
the equator (two times each year), the
Earth is experiencing an equinox (equal
night). It is vernal (spring) equinox in
March (on or about March 21), and the
autumnal (fall) equinox (on or about
September 21).
The solstices and equinoxes have a
huge impact on the Earth’s
ecosystems.
Earth’s position in our solar system is considered the “green
zone”, or habitable zone. It is in the zone where liquid
water is possible…and liquid water is important to life.
As you can see, in our
solar system, Earth is
the only planetary body
within this zone.
The tilt of the Earth’s
axis, and latitude of a
location are largely
responsible for the
various climate types on
Earth.
As you can see, there are patterns to climates that become
obvious. You can predict, based on latitude, altitude, and
distance from oceanic influence, the type of climate an
area will have.
In polar regions, latitude plays a vital role. Since
the farthest north, or south the direct rays of
the Sun ever reach are 23 ½ °, regions beyond
that would tend to be cooler. The farther you
are from the Sun’s influence, the colder the
place. Can’t get much further than the poles!
Another large influence in the northern and
southern hemisphere is the relative amounts of
landmass. Far more in the northern hemisphere
means relatively colder temperatures.
The same can be said of mid-continental regions,
which find themselves far from any type of
temperate oceanic influence. These regions tend to
be relatively colder too.
While in the southern hemisphere, more oceanic
influence means relatively warmer temperatures.
You can see from these examples how latitude plays
a more influential role than altitude does, when
determining global ecosystem placement.
The Tropics lie between the Tropic of Cancer, (23.5 degrees
north latitude) and Tropic of Capricorn (23.5 degrees south
latitude), and experience mostly warm and wet conditions,
however regions away from oceanic influence (such as the
African Savanna), may be seasonally dry.
Climate in the Tropics does not change much, due
to a fairly constant amount of daylight, and the
consistent angle of the sun’s rays.
The latitudes around 66° north and 66° south are known as the Arctic
and Antarctic Circles respectfully, and represent the Polar regions.
From the 66th parallels to the poles direct sunlight is never a factor.
Yet, it is above these lines of latitude that the sun may stay visible for
the entire day. This happens on the Summer Solstice (June 21 st in the
northern hemisphere, and December 21st in the southern hemisphere)
Polar biomes include the Penguins:
South
Tundra, which are areas
Polar Bears:
of low growing grasses
North
and mosses. Trees
cannot grow in the
Tundra because of the
permafrost.
Grazing mammals, some
of whom are well
camouflaged, are well
adapted to the Tundra.
Camouflage also works
well for the predators!
Globally located between the Tropical and Polar Zones are
the Temperate Zones. Direct rays of the Sun vary greatly
within this zone, unlike the others. In these regions,
climate will vary in a range between Polar Climates in the
winter months, and Tropical Climates in the summer
months. The Temperate Zone is known for its many
different biomes, as a result.
Biomes found within this
region include:
• Taiga
• Temperate Deciduous
Forest
• Grassland
• Desert
The coldest and driest temperate zone Evergreen trees are well
adapted to the Taiga, because
is the Taiga. Here there are large
they require little water, and
forests of conifers, cone bearing
evergreens. Winter is harsh but shorter their branches point
than in the tundra and therefore there downward to resist the weight
is no permafrost, allowing for roots to of snow which is plentiful.
They also have needle-shaped leaves
penetrate the soil.
with a thick waxy cuticle to
protect them from the cold dry air
(as this cross section shows).
Animals of the taiga have
adapted thick winter coats,
or migration patterns that
remove them from the harsh
environment during winter.
On a global scale, taiga is the largest
biome on Earth, and it is only found
in the northern hemisphere.
Between the taiga and the tropics we have an area whose
definition greatly depends upon the amount of rainfall. In
this area biomes may range from deciduous forest (greatest
rainfall), to grassland (less rainfall), to deserts (least rainfall).