OBJECTIVE 14

• Trace biogeochemical cycles through the environment, including water, carbon, oxygen, and nitrogen Relating natural disasters, climate changes,

nonnative species, and human activity to the dynamic equilibrium of ecosystems

Describing the process of ecological succession

Biogeochemical Cycles

The Water Cycle

1. CONDENSATION • Water vapor in the atmosphere condenses to form clouds.

2. PRECIPITATION: • Water falls to the Earth’s surface in the form of precipitation

(rain or snow).

3. EVAPORATION and TRANSPIRATION: • Remaining water is heated by the sun and reenters the

atmosphere by evaporation….OR• Some seeps into the soil becoming part of groundwater.

Water is taken up by the roots of plants, passes through the plants, and reenters the atmosphere by transpiration (evaporation from leaves).

The Water Cycle

The Water Cycle

The Carbon Cycle

1. Carbon gas is in the atmosphere.2. PHOTOSYNTHESIS:

• Carbon dioxide in the air or dissolved in water if used in by plants, algae, or bacteria in photosynthesis and then release oxygen back into the atmosphere.

3. RESPIRATION, COMBUSTION, OR EROSION• Respiration: All living organisms use take in oxygen for respiration

and release carbon dioxide back into the atmosphere. • Combustion: Carbon returns to the atmosphere through

combustion or burning of wood or fossil fuels.• Erosion: As limestone erodes, the carbon becomes available to

other organisms.

The Carbon Cycle

The Oxygen Cycle

1. Oxygen is in the atmosphere.2. Respiration: ALL living things take in oxygen

from the atmosphere and release carbon dioxide.

3. Photosynthesis: Plants take in carbon dioxide and release oxygen back into the atmosphere.

The Oxygen Cycle

The Nitrogen Cycle1. N2 (nitrogen gas) makes up about 78 percent of the

atmosphere.2. Nitrogen fixation: Nitrogen-fixing bacteria that live in the soil

take nitrogen from the atmosphere and change it to a form that organisms can use (ammonia or NH3).

3. Ammonification: Bacteria produce ammonia from decaying matter.

4. Nitrification: Nitrate is produced from ammonia by the nitrogen-fixing bacteria.

5. Assimilation: Plants absorb nitrogen and use it to form organic compounds.

6. Denitrification: Nitrate is converted to nitrogen gas and release back into the atmosphere.

7. Organisms eat the plants, and the get rid of the nitrogen in the form of waste. The nitrogen returns to the soil.

The Nitrogen Cycle

Ecosystem Equilibrium

Natural disasters

• Hurricanes, Tornadoes, Fires, Landslides, Floods, Droughts, etc.– Can wipe out entire populations within an

ecosystem– Can sometimes move entire populations to a new

location

Climate changes

• Organisms must adapt to new climates or migrate to a new location to survive

Nonnative species

• Interrupting the food chain• Habitat degradation• Diseases

Human activity

• Human-induced environmental changes– Acid Rain

• Caused by coal-burning power plants (sulfur combines with water vapor in the atmosphere to produce sulfuric acid)

• Dying lakes and damaged forests due to pH acidity in the environment

– Ozone Hole• Allows more ultraviolet radiation to read Earth’s surface causing

an increase in human diseases such as skin cancer, cataracts, and cancer of the retina

• Major cause: CFCs (chlorofluorocarbon chemicals) found in coolants in refrigerators and air conditioners, aerosol propellants in spray cans, plastic-foam cups and containers; use is now limited

Human activity

• Human-induced environmental changes– Global Warming• Large increase in carbon dioxide in the Earth’s

atmosphere related to burning of fossil fuels that has accompanied forest clearing and urban industrialization• Caused by the greenhouse effect – chemical bonds in

the carbon dioxide molecules absorb solar energy as heat radiates from the Earth trapping the heat

– Chemical Pollution• Industrial and Agricultural

Human activity

• Human-induced environmental changes– Loss of Resources• Extinction of species

– Destruction of habitats

• Loss of Topsoil– Turning over to eliminate weeds– Allowing animals to overgraze ranges and pastures– Poor land management

• Ground-water pollution and depletion– Wasted on watering lawns, washing cars, leaky and inefficient

faucets and toilets– Polluted by irresponsible disposal of chemical wastes

Human activity

• Human-induced environmental changes– Human Population Growth

Ecological Succession