Biogeochemical Cycles

Biogeochemical Cycles

• There are 94 elements that are naturally occurring

• Most of them find their way into biotic systems in some way

• However it is important to know where they come from

Biogeochemical Cycles• We have done the basics

of biogeochemical cycles• We talked about the

water cycle and how it redistributes water around the planet

• This cycle changes water to different states of matter and moves it around

• These cycles can be local or global

Biogeochemical Cycles

• However there are many different biogeochemical cycles

• The other major cycles are the carbon cycle, nitrogen cycle and the phosphorous cycle

• These cycles all move nutrients around the planet in different forms

Biogeochemical Cycles• Each of these cycles use

organic matter and abiotic reservoirs to house different forms of chemicals

• Organic matter is tissue that makes up living systems

• Abiotic reservoirs are areas outside of living things that will store the chemical

Carbon Cycle

• Carbon is the major ingredient on all organic matter– Remember that organic

chemistry deals with carbon based chemistry

• It is present in the atmosphere, soil and (to a lesser degree) our water

Carbon Cycle• Understanding how the

carbon cycle works is important because it is one of the major causes of climate change

• Carbon in the atmosphere takes the form of CO2

• CO2 is one of the major green house gasses due to its structure and abundance

How It Works

• The carbon cycle is based on two major reactions

• Photosynthesis

• It is also based on the reaction that is the reverse of photosynthesis

• Cellular Respiration

How It Works

• Since there is no starting point, lets start with carbon in the atmosphere

• This carbon in the form of CO2 is a gas

• That gas is taken in by cells of green producers

How It Works

• The CO2 will then change forms to sugars– Basic structure of C6H12O6

• This form of carbon will then be passed to consumers that eat leaves, fruits or bark of the plant

• The carbon will be incorporated to their organic matter

How It Works

• At this point larger consumers will consume the smaller consumers

• These organisms will be converted to different forms of organic matter inside the predator

How It Works

• While in the consumer system, organisms are releasing waste, breathing and dying

• Breathing releases CO2 back into the atmosphere

• Releasing waste and dying introduces carbon to the soil

How It Works

• Once carbon is in the soil, it is attacked by decomposers

• The decomposers breakdown the detritus and release CO2 back to the atmosphere

• This competes the cycle

Human Input

• However, humans are greatly affecting this cycle

• We are releasing large amounts of CO2 into the atmosphere by humans tapping into decomposing or decomposed organisms

Human Input• Fossil fuels are organisms

that have decomposed and have been buried at different depths

• Depending on the pressure, and heat at where they are buried determines the type of fossil fuel

• All of these fuels contain a large amount of carbon

Lets Draw It!

Composition of Air• Air is composed of different

compounds and elements• It has around around 78%

Nitrogen – In the form of (N2)

• It has around 21% oxygen – In the form of (O2)

• It is composed of around 1% other compounds– Argon – CO2

Composition of Air

• This makes nitrogen the most common gas in our environment

• You would think that it would be abundant and easy to use

• However nitrogen is a difficult material to convert from a gas

Nitrogen Fixation

• In order to have nitrogen in a useable form it has to change from the N2 in air

• The nitrogen must be put in a usable form

• One useable form is ammonia

Nitrogen Fixation

• In order for a N2 to be converted to NH3 there has to be a way for it to change

• Nitrogen will not spontaneously convert to ammonia

• There needs to be a process• The process of turning N2

into useable NH3 is called nitrogen fixation

Mycorrhizal Bacteria

• In soil the place that has the most life is right next to the roots of plants

• This is because many microorganisms live in this area

• We call this area the rhizosphere

Mycorrhizal Bacteria• This area around the roots

contains a wildly diverse ecosystem– Fungi– Bacteria– Nematodes– Protozoa

• A gram of soil from the rhizosphere can contain 50 million to 1 billion microorganisms

Mycorrhizal Bacteria

• Bacteria that live right around the roots are called mycorrhizal bacteria

• These bacteria are close enough to interact with the plant and can form a symbiotic relationship with the plant

Mycorrhizal Bacteria

• Legumes are plants with dry fruit that have a symbiotic relationship with mycorrhizal bacteria

• They contain a simple dry fruit

• They contain– Many Beans– Peanuts– Alphalpha

Mycorrhizal Bacteria

• Most legumes can support bacteria that fix nitrogen

• These bacteria form nodes or “bumps” on the roots of these plants

• These bacteria fix nitrogen

Nitrogen Cycle• Once again because it is a

cycle, there is no beginning or end to the nitrogen cycle

• Lets start with atmospheric nitrogen as N2

• It is taken in by nitrogen fixing bacteria and is converted to ammonia (NH3)

• It can also be converted to NO or NO2 by lightning

Nitrogen Cycle

• NO and NO2 can be used by a plant

• NH3 needs to pick up a free hydrogen to become ammonium (NH4)

• NO, NO2 and NH4 can all be used by a plant

• They are incorporated by the plant

Nitrogen Cycle

• The rest we know…• Consumers eat the

plants and release waste and die

• Other consumers eat the primary consumers and release waste and die

• A large quantity of nitrogen is in introduced to the soil

Nitrogen Cycle

• When in the soil decomposers will use the nitrogen

• Also bacteria known as denitrifiers will take in NH3 from the soil and release it as N2

• This N2 finds its way back to the atmospheric reservoir

Human Impact

• Humans can greatly impact this cycle by adding nitrogen to the soils

• Humans do this by adding fertilizer to fields, crops and farms

• This greatly increases the amount of nitrogen in the soil

The Human Impact

• Humans adding nitrogen can be very harmful

• Excess nitrogen can be captured in runoff

• This runoff is then carried to the ocean were it causes an algae bloom

The Human Impact• An algae bloom is very

destructive to an ecosystem

• It chokes the life out of all manner of sea life

• Without this sea life, there are no primary consumers to feed secondary consumers

• It can wipe out large sections of open water

The Human Impact

https://www.youtube.com/watch?v=OUeAMzoKNWg

https://www.youtube.com/watch?v=5X8ZiycqIlY

Lets Draw It!

Erosion• Have you ever looked at

the amount of rocks on the earth?

• There are a really large number of rocks that contain minerals that are needed in living systems

• Since most organisms cannot digest solid rock, the minerals in them have to be unlocked in other ways

Erosion

• Rocks can be slowly broken down over time if they undergo the process of erosion or weathering

• This is the gradual breakdown of the rock into much smaller sizes

• These smaller rocks will continue undergo erosion and weathering

Erosion

• Once these rocks are broken up sufficiently they can be incorporated into the soil

• The soil then takes on the properties of the rocks that compose it

• This is why there are different soil types in different areas

Phosphorous Cycle

• The erosion of rock releases one of the most limited nutrients into the soil

• Phosphorous is a very limited nutrient in most ecosystems

• Remember it is a central part of DNA, ATP and phospholipids

Phosphorous Cycle

• However when rocks erode they release the nutrient into the soil

• This allows access of phosphorus to plants and other producers

• They will incorporate this into their living tissue

Phosphorous Cycle

• Consumers then will eat the producers

• Other consumers will then eat the primary consumers

• The consumers will use the phosphorous in their living tissues

Phosphorous Cycle

• The consumers will then release waste or die and return phosphorous back into the soil

• Decomposers will then use that phosphorous in their tissues

Back to Rock• The cycle would not be

complete if phosphorous was not going back to rock

• Sediment and soil that washes into waterways will settle at the bottom

• These soils and sediments will find a resting place at the bottom of a lake, river or ocean

Back to Rock

• The sediments will eventually be packed down by layers of sediment on top of them to create sedimentary rock

• Eventually this rock will find its way to the surface and will be the rock that is eroding and weathering

Lets Draw It!