The nutrient cycles you should be thoroughly familiar with are:• Carbon, • Hydrologic, and • Nitrogen.

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!

You may also see the phosphorus cycle show up on the AP test. This is the simplest cycle. Most of the phosphorus found in the phosphorus cycle originates in the rocks beneath your feet. (if a cycle has an origin).

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

• Largest Carbon sink: Ocean (dissolved CO2) and shelled organisms (CaCO3)

Carbon is also found in our fossil fuels, and when we burn them (combustion), we add the original carbon from the organisms that 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.

EnergyThe 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.

Energy In EcosystemsSince 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.

Fossil Fuel ResourcesAbout 86% of the world’s commercial energy is supplied by fossil fuels. From least to most efficient:Coal: Most plentiful, and cheapest…but least environmentally friendly.• Peat (compressed plant material)• Lignite (sedimentary, with some

fibers)• Bituminous (sedimentary) • Anthracite (Metamorphic)

The less efficient forms produce more sulfur when burned. This adds SO2 to the atmosphere, which in turn can produce sulfuric acid rain when combined with H2OCrude 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

Renewable EnergyTypes 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.

Other Renewable EnergiesHydroelectric

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

Solar EnergyRelies 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.

Renewable Energy, ContinuedWind Energy

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

Ocean EnergyBoth 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)

Geothermal EnergyRoughly 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 USIceland, 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 emissionsEnergy 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. In 1975, Congress enacted the Energy Conservation Act. The Corporate Average Fuel Economy (CAFÉ) standards were added to this act as an amendment.

Fuel efficiency for cars rose markedly between 1973 and 1985 because of this act.

Nuclear EnergyThe two types of Nuclear Energy are: Fusion, and FissionFusion:

Fission:

Example…the energy from the sunFuel is very small nuclear elements, such as hydrogen, which fuse together to form heliumNot 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!

Uses a fuel of very large radioactive elements, such as Uranium and Plutonium, and forces them to split apart in a nuclear reaction. When this occurs in a controlled manner, heat is also released. The heat is used to heat water to form steam, which is used to turn a turbine, which generates electricity. Problems include the toxicity of the waste, which is at present stored in large steel drums and buried in landfills. Benefits include relatively cheap energy, with low emissions. It is a far cleaner alternative to fossil fuels.

Some important incidents in Earth History include two notable nuclear disasters.Chernobyl: Ukraine, used graphite to enclose the core. A fire in the core enabled nuclear fuels to escape and cause environmental devastation.Three-Mile Island: near Harrisburg, Pa. Resulted in a partial core melt-down, releasing radioactive gases

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:

Genetic Diversity

Species Diversity

Ecological Diversity

Functional Diversity

The variety of genetic material within a species or a population

The number of species in different habitats

The variety of terrestrial and aquatic ecosystemsThe 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.

EPA

Endangered Species ActWhile 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.

Bleak, but accurateMany 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 most cases, humans will put the good of themselves, or their families, over the good of the community.

Natural Selection and EvolutionCharles Darwin

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.

Earth’s Components and CharacteristicsThe 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:

• Archaen:

• Proterozoic:

• Phanerozoic:

No rocks have survived from this eon, which is the oldest. Earth was barren, with no atmosphere.

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. 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. 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.

PERMIAN MASS EXTINCTIONThe 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 with extinction events in our geologic history.

Earth’s tectonic plants have driven the continents since their formation early in Earth’s childhood.

There are three types of boundaries.• Transform

• Convergent

• Divergent

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. 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. 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.

Seasons on EarthThe 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 21st in the northern hemisphere, and December 21st in the southern hemisphere) Polar biomes include the Tundra, which are areas of low growing grasses 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!

Penguins: South

Polar Bears: North

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 is the Taiga. Here there are large forests of conifers, cone bearing evergreens. Winter is harsh but shorter than in the tundra and therefore there is no permafrost, allowing for roots to penetrate the soil.

On a global scale, taiga is the largest biome on Earth, and it is only found in the northern hemisphere.

Evergreen trees are well adapted to the Taiga, because they require little water, and their branches point downward to resist the weight of snow which is plentiful.

They also have needle-shaped leaves 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.

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).