UNIT 1

SUSTAINING ECOSYSTEMS

Chapter 2

Biogeochemical Cycles

Science 10

Change & Recovery in Ecosystems

(you do not need to copy)

What happens to the

materials that make up

a truck when it begins

to rust?

What happens to the

tree after it dies?

Cycling of Matter in Ecosystems Organic substances

Contain atoms of Carbon and Hydrogen

Are broken down into simpler forms in living things

Ex. Sugar, carbohydrates, proteins, amino acids

Inorganic substances Do not contain combination of

carbon and hydrogen Ex. Water (H2O), ammonia

(NH3), Carbon dioxide (CO2)

Elements Essential to Life

Carbon

Hydrogen

Nitrogen

Oxygen

Phosphorus

(Sulfur needed for protein

production. Not DNA)

Why do we

NEEEED

these

elements?

All elements

needed for DNA!

Biological Processes Involved in Nutrient

Cycling1. Photosynthesis

Using Sun’s light energy, Plants convert CO2

and H2O into O2 and sugar

6CO2 + 6H2O → C6H12O6 + 6O2

2. Respiration

Animals use O2 and sugar, converting it to CO2

and H2O

C6H12O6 + 6O2 → 6CO2 + 6H2O

More Processes3. Decomposition

• Remains of dead organisms are broken down by bacteria and fungi

• All molecules are released into soil

4. Excretion• Waste material from animals is broken down and

returned to the soil

5. Assimilation• Conversion of molecules (by bacteria) into a useable

form (for plants).

• Nitrification, denitrification

Cycling of Organic Matter

The atoms and molecules available to make up organisms on earth is limited

All the atoms MUST be recycled in order for new organisms to form. It is very likely that at least one

of the carbon atoms in your body was also in a 70 million year old dinosaur

(Don’t need to copy)

Recycling of Matter by Micro-organisms

(Don’t need to copy)

The Matter Cycle

Soil

Grass

CowPerson

Decomposers

1. Dead plants and animals are broken down

by decomposers – their atoms / molecules

are released into the system to be re-used

2. Atoms, molecules accumulate in the soil

3. Nutrients are taken up by grasses

4. Cows eat the grass – nutrients and atoms

are passed on to the cow

5. Person eats cow – nutrients and atoms are

passed on to person

6. Each of these things can die, the atoms are

broken down by decomposers and

recycled for the next living things

(Don’t need to copy)

The Oxygen Cycle

Photosynthesis:

6CO2 + 6H2O C6H12O6 + 6O2

Respiration:

C6H12O6 + 6O2 6CO2 + 6H2O

What do you notice about these two chemical

reactions?

The Oxygen Cycle

Oxygen

(in atmosphere)

RESPIRATIONby plants, animals and decomposers

Carbon Dioxide

(in atmosphere)

PHOTOSYNTHESIS

by green plantsCombustion

(burning stuff)

(Don’t need to copy)

The Carbon CycleCO2 in the atmosphere

volcanic

eruption

CO2

dissolved in

water

Ocean

sediment

combustion

Fossil fuelsConversion to fossil fuels

Decomposition

Glucose

Photosynthesis - carbon

is stored in the biomass

Aerobic

respiration

Weathering

(Don’t need to copy)

The Carbon Cycle

Two groups of carbon sources in the

carbon cycle

1. Biotic - Aerobic respiration (in the presence of

O2), and decomposition

The organic reservoirs (storage areas) for

carbon are the bodies of living things

2. Abiotic - Combustion and geological activity

The inorganic reservoirs for carbon are

the atmosphere, the oceans, and the

Earth’s crust

(Don’t need to copy)

Monday’s Lesson is Complete

The Nitrogen CycleNITROGEN

is a component of many organic molecules.

forms an essential part of amino acids (the building

blocks of proteins) and

forms part of DNA.

essential for all living cells.

in gas form (N2) makes up about 78% of atmosphere.

The Nitrogen Cycle

Most organisms cannot use nitrogen in the gaseous

form found in the air we breathe, so it must be in

“fixed” forms that plants can absorb.

So how do you “fix” N2? There are 3 ways…get

ready for the ABC’s of Nitrogen “fixing”…

The Nitrogen Cycle ~ 4 ProcessesProcess #1 ~ NITROGEN FIXATION (must “fix” N2 so it

can be absorbed by Plants and get into food chains).

Atmospheric fixation - lightning breaks

nitrogen bonds they combine with oxygen

in the air forming nitrogen oxides these

dissolve in rain, forming nitrates nitrates

rain only earth plants absorb nitrates

only a small amount is fixed

this way ~ about 10%

Nitrogen Fixation (cont.)

Biological fixation – Bacteria are the only

organisms able to take N2. They combine it with

hydrogen to make ammonia (NH3).

Most are free-living in soil.

Some have developed an association with

certain plants. In return for sugars from the

plant, these bacteria fix nitrogen which can

be used by the plant for growth. bacteria fix 60% of nitrogen gas

Nitrogen Fixation (cont.)

Commercial (industrial) fixation – Smarty

pants people figured out a way to convert N2

into ammonia (NH3) too!

Today, about 30% of the total fixed nitrogen

is manufactured in ammonia chemical plants. See? The ABC’s of fixing nitrogen! You’re welcome ;-)

The Nitrogen Cycle ~ 4 Processes

Specialized nitrogen-fixing bacteria convert

ammonia into nitrites (NO2–)

Another type of specialized bacteria transforms the

nitrites into nitrates (NO3–)

BAM! Plants can easily absorb nitrates and use

them to form proteins (food chains!).

Process #2 ~ NITRIFICATION

The Nitrogen Cycle ~ 4 Processes

decomposers break down the molecules in excretions

and dead organisms into ammonia (NH3) and

ammonium (NH4+) (remember that polyatomic?)

most of the ammonia produced by decay is

converted into nitrates by those special nitrifying

bacteria.

Process #3 ~ DECAY (another way ammonia is produced)

The Nitrogen Cycle ~ 4 Processes

The only process that puts nitrogen back into the

atmosphere.

Yet another specialized bacteria starved of oxygen strip

away oxygen from any unused nitrates (NO3−)

(Hey…bacteria need to breathe too!)

Once oxygen has been stripped away, the nitrogen bond

with each other (N2) and return to atmosphere again.

Process #4 ~ DENITRIFICATION (Once again bacteria to the rescue!)

Nitrogen Cycle ~ review 1…

Nitrogen Cycle ~ review 2…

Nitrogen Cycle ~ review 3…

Lesson Complete

This one you’ll need to study eh?…

Phosphorus Cycle

Phosphorus is somewhat abundant in organic matter, accounting for ~0.2% of biomass

Its largest store is rocks and minerals, but it is rarely abundant within food chains. (That is why it’s a component of artificial fertilizers).

The key nutrient is phosphate (PO43-), which

often limits plant productivity, especially in freshwater.

It is the slowest of the matter cycles.

The Phosphorus Cycle

Eutrophication

The eutrophication of the Potomac

River is evident from the bright

green water, caused by a dense

bloom of cyanobacteria.

• Caused by an oversupply of nutrients, which causes

explosive growth of plants and algae. When these

organisms die, they consume the oxygen in the body of

water, decreasing oxygen levels (1% - 30% dissolved

oxygen. Fish need 80%).

• Phosphorus is the main culprit but excessive nitrogen

is problematic as well. (Both of which are found in

artificial fertilizers).

• The source of these excess phosphates are detergents,

industrial/domestic run-off, and fertilizers.

• dominant contributors to eutrophication

industrial/domestic run-off and agriculture.

• Due to human activities, the amount of nitrogen has

doubled in the last 50 years.

Agricultural practices often use large amounts of nitrogen-containing fertilizers.

Excess nitrogen is washed away, or leaches, into the waterways.

This promotes huge growth in aquatic algae called algae blooms.

Algae blooms use up

all CO2 and O2 and block sunlight

killing many aquatic organisms.

Algae blooms can also produce

neurotoxins that poison animals.

Bioaccumulation & Bioamplification

Bioaccumulation

Increase in concentration

of a pesticide from the

environment in all

organisms in a food chain.

Often insects consuming

herbicides.

Bioamplification

The higher up the food

chain, and thus the higher

the trophic level, the higher

the concentration of toxins.

Top carnivores end up with

the greatest concentrations

of toxins.

Bioaccumulation

Bioamplification