Bell Ringer 12.1•Describe the three main trophic levels.

•What does the 10% Law?

•Compare food chains to food webs.

•What are the three types of pyramids we discussed yesterday? What information can you get from each?

Nutrient Cycles and Human Impact

What is Nutrient Cycling?•BIOGEOCHEMICAL CYCLES: passage

of matter from one organism to another in the biosphere.

•Nutrients are finite (not like the sun which supplies constant energy), so they must be (re)cycled through various parts of nature.▫Relies heavily on DECOMPOSERS and

MOVEMENT through the cycle (not getting “stuck” in one area)

•Major Biogeochemical Cycles:▫Carbon, Water, Nitrogen

If elements are to be recycled in nature, which organism must be present?

A. DecomposersB. PredatorsC. HerbivoresD. Parasites

Carbon Cycle•Carbon cycles through the ecosystem

mainly by…▫PHOTOSYNTHESIS: takes carbon out of

the atmosphere in the form of CO2 (performed by plants)

▫RESPIRATION: puts carbon into the atmosphere in the form of CO2 (performed by all living organisms)

Photosynthesis

Respiration

O2+ C6H12O6 H2O + CO2

In the carbon cycle, carbon is transferred from animals to plants by which of the following?

A. Carbon dioxideB. OxygenC. SugarsD. Water

Besides photosynthesis, why is it important to have CO2 in the atmosphere?

•Many gasses found in Earth’s atmosphere help trap HEAT

•Works like a greenhouse, so is called the GREENHOUSE EFFECT

•Important because Earth would be too cold for life without it.

•CO2 is important to have in the atmosphere because it is one of the gasses that contribute to the greenhouse effect.

Human Impact on the Carbon Cycle•Combustion of fossil fuels: burning of

coal, oil, and natural gas add extra CO2 to the atmosphere

•Deforestation: cutting down large areas of trees reduces the amount of photosynthesis leaving more CO2 in the atmosphere.

What is the main suspected environmental problem associated with the burning of fossil fuels?

A. Depletion of fresh waterB. Depletion of ozoneC. Global coolingD. Global warming

Why should we be concerned about adding more CO2 to the atmosphere?

Too much CO2 can cause changes in climate by making the Earth too warm.

Why should we care if Earth is getting warmer?Even if Earth warms by only a few degrees, there will be big impacts on weather and ecosystems all over the planet.

FLOODING

DROUGHT

POLAR ICE MELTING

How else do the actions of humans affect the atmosphere and Earth’s ecosystems?

COMBUSTION OF FOSSIL FUELS releases sulfur and nitrogen into the atmosphere in addition to CO2

The sulfur and nitrogen combine with water in the atmosphere to form ACID RAIN

Effects of Acid Rain:• Damages soil,

roots, and leaves of trees• Changes the pH

of rivers/streams and may kill plants & animals in the water• Damages

buildings, statues, and bridges

Volcanic eruptions may also affect the atmosphere and Earth’s ecosystems.•Releases sulfur into

the atmosphere which helps to form acid rain

•Extremely large eruptions may release enough ash to block sunlight global cooling

The Water CycleMAJOR PLAYERS:•Precipitation

•Evaporation

•Transpiration

•Run-off

•Groundwater

How Humans affect the Water Cycle

• Humans use water:▫Agriculture▫Dams and deforestation▫Urbanization (living in cities)▫Overuse of aquifers (groundwater)

Saltwater intrusion (ocean) Subsidence (lend to collapse)

• Clean water supply▫1 billion people (16%) do not have any

access to clean water▫Can cause outbreaks of disease

Examples: cholera, hepatitis, mosquito breeding

• Acid Rain▫Hurts plants, animals, and buildings

When deforestation occurs in an area, what immediate effect does this have on the water cycle?

A. More precipitation is formed.B. There is less runoff water.C. More water is returned to the

atmosphere.D. Less water is returned to the

atmosphere.

The Nitrogen CycleIMPORTANCE:•78% of the air is nitrogen•All organisms need nitrogen•Nitrogen is present in DNA and RNA and

in amino acids (proteins)•The food chain largely moves nitrogen

around•Bacteria and lightning take nitrogen gas

and puts it into a useable form▫Process called NITROGEN FIXATION▫Some bacteria have mutualistic

relationships with plants and live on their roots

Which of the following statements about the nitrogen cycle is true?

A. Although nitrogen is the most abundant atmospheric gas, plants cannot use it from the air.

B. Adding man-made fertilizers to farm fields will take needed nitrogen from the cycle.

C. The occurrence of lightning takes extra nitrogen molecules from the atmosphere and the cycle.

D. Bacteria located in the soil trap excess atmospheric oxygen and help it enter plant roots.

How Humans affect the Nitrogen Cycle•Humans contribute extra nitrogen in the

cycle due to fertilizers and animal waste (hog lagoons) runoff into the lakes and rivers.

•Excess nitrogen can cause eutrophication which encourages extra algae to grow (algal bloom) lowering levels of oxygen causing fish kills.

Remember, energy flows as nutrients cycle!

1. What benefit does the carbon cycle provide to ecosystems?

2. What problems can carbon dioxide cause? 3. Describe what contributes CO2 to the atmosphere. 4. Describe what pulls CO2 from the atmosphere.

5. Where is the majority of CO2 stored?

6. How does fossil fuels/deforestation affect the carbon cycle

7. How is the nitrogen cycle beneficial for plants? 8. How do decaying plants contribute to the nitrogen

cycle? 9. What role do bacteria play in the nitrogen cycle? 10.How would the absence of bacteria affect the

nitrogen cycle? 11.What consumer is essential for the function of the

nitrogen cycle?12.Explain the water cycle.