Cycling of Matter in

Ecosystems

Biogeochemical Cycles• Matter cannot be made or destroyed.• All water and nutrients must be produced or

obtained from chemicals already present in the environment.

• This happens through biogeochemical cycles - the movement of matter through biotic and abiotic environment.

• Nutrients are all the chemical substances that an organism needs to survive.

• A nutrient cycle shows how nutrients move between organisms and the environment.

• The following cycles are especially important:•water cycle• carbon cycle• nitrogen cycle• phosphorus cycle

In general,• producers get nutrients from the soil• consumers get nutrients from eating producers or

other consumers• decomposers return nutrients to the soil through

decomposition

• Atoms last forever.• All the atoms found on Earth today are the same as

those that were present when Earth first formed.• Every atom that makes up your tissues has a history!• Every 7 years each atom in your body is replaced

Recycling of Atoms

Carbon

Cycle

Carbon Cycle• The biogeochemical cycle in which carbon is cycled through

the lithosphere, atmosphere, hydrosphere, biosphere.• Carbon is an important element, because it is the basic

building block of living things.• Carbon is recycled in the carbon cycle through several

processes, but mostly through photosynthesis and respiration.

• The concentration of carbon in living matter (18%)is almost 100 times greater than its concentration in the earth (0.19%).

• So living things extract carbon from their non-living environment.

• For life to continue, this carbon must be recycled.

• Carbon is important for many processes– Photosynthesis and Respiration– Animal shells– Getting energy (fossil fuels)

What’s So Special About Carbon?

Where is all the Carbon?

• Inorganic Carbon– The

Atmosphere– The Ocean– The Earth’s

Crust• Organic Carbon– Bodies of

Living Things– Fossil Fuels

• Most of the carbon on earth is locked up in the crust in limestone rocks: CaCO3

• Some is in living & dead biological tissue (biomass)

Some is in fossil fuels: coal, crude oil and natural gas.

Coal = carbonMethane = CH4

• Some is in the atmosphere as CO2

• A lot is dissolved in seawater as: - carbonate (CO3

2-) - bicarbonate (HCO3

-)- carbonic acid (H2CO3)- carbon dioxide (CO2)

• Primarily photoautotrophs, like plant and algae that use the energy of light to convert CO2 to organic matter.

Carbon enters the biotic world through the action of autotrophs

Carbon returns to the atmosphere by • respiration (as CO2)

• burning• Decay (producing CO2 if oxygen is present,

methane (CH4) if O2 is absent.

The uptake and return of CO2 are not in balance.

Photosynthesis

Short Carbon Cycle

Cellular Respiration

When organisms die, their carbon molecules are returned to the soil by decomposers and are released to the air as carbon dioxide.

Carbon Dioxide

Bacteria

Sometimes dead organisms are changed over millions of years into carbon-based fossil fuels like coal and gas

Human Impact on the Carbon Cycle

• Humans are having a big impact on the Carbon Cycle by:– releasing carbon into the atmosphere faster

than would normally occur by burning fossil fuels, returning to the atmosphere carbon that has been locked within the earth for millions of years.

– Clearing away vegetation. In recent decades, large amounts of Amazon rain forest have been cleared for agriculture and cattle grazing.

• The carbon dioxide content of the atmosphere is gradually and steadily increasing– Since measurement of CO2 began in the late

19th century, its concentration has risen over 20%.

The Greenhouse Effect1. Sun’s rays enter

the Earth’s atmosphere

2. Heat is reflected back from the Earth’s surface

3. Heat is absorbed by carbon dioxide (greenhouse gas) and as a result becomes trapped in the Earth’s atmosphere

4. The Earth becomes hotter as a result

Home Fun!

• Page 51– Q 3, 4, 5b

• Page 69– Q 20

• Page 70– Q 8, 14