1. Natural Cycles
Only few of the known elements found in the upper crust of the Earth in water or the atmosphere are abundant in tissues of living organisms like carbon, hydrogen, oxygen, or nitrogen.
Circular flow of elements from living organisms to nonliving matter is the elemental cycle.

2. The Carbon Cycle
Carbon is the most abundant element in living organisms
In the absence of water, nearly half of dry matter in bodies of animals or humans consists of carbon
The Carbon Cycle occurs as carbon atoms flow continuously from living organisms to the atmosphere, the oceans, and the soil

3. The Nitrogen Cycle
Nitrogen fixation also occurs naturally in the atmosphere when lightning strikes
Nitrates are released from animal wastes and decaying plants and animals

4. The Water Cycle Water is 70% of plant and animal weight
Water controls the temperature of organisms and is a nutrient solvent
Water dissolves nutrients and carries them to tissues that need them
Water stores heat and maintains constant temperature in the environment

5. CO2 and Global warming
Research has demonstrated that sea water algae are capable of removing large amounts of CO2 from the atmosphere.
Adding iron as a nutrient to the water surface can simulate the algae growth.
Some scientist worry that promoting algae growth on a massive scale could upset the balance of the ecosystems of the oceans.

6. The Nitrogen Cycle
The circular flow of Nitrogen from free gas in the atmosphere to the Nitrogen compounds such as nitrates in the soil and back to the atmospheric Nitrogen is know as the Nitrogen cycle.
Nitrogen makes up about 80% of the air supply.
Odorless gas that cannot be used by plants or animals.

7. The Nitrogen Cycle cont.
Must be combined with oxygen, or other elements before it becomes available as a nutrient for living organisms.
Nitrogen Fixation- a process by which nitrogen gas is converted to nitrates.
Nitrogen – fixing bacteria- are able to convert nitrogen gas to nitrates.
Clover, beans, peas, and other legumes are able to make their own nitrogen fertilizer.
Types of blue/green algae and fungi also are capable of nitrogen fixation.

8. The Nitrogen Cycle Cont.
Several Industrial processes also convert Nitrogen gas to nitrates.
One Process converts the gas to ammonia as a by product of steel production.
Ammonia can also be obtained directly from natural gas.
It is then converted to a form of nitrate that can be used for fertilizer.
Denitrification occurs when some forms of bacteria come into contact with nitrates.
Similar processes occur when nitrates are carried by runoff water into surface water, which constantly exchanges nitrogen with the atmosphere.

9. The Water Cycle
. Water is one of the most important recourses in the environment
. Provides living environment and helps growth of plants
. 70% of the weight of living plants and animals is water
. Need water to survive
. Water stores heat and helps maintain a more constant temperature
. Soil break down from the water flow

10. . Water moves in forms of rain or snow, from the ocean to the atmosphere, to the soil, to the streams and rivers and then back to the ocean
.Solar energy and the force of gravity is how it drives the cycle.
. Source of heat causes water to evaporate from the ocean is solar energy.
. More water enters the atmosphere by evaporating from the soil and plant surfaces
. Transpiration is when plants give up large amounts of water to the atmosphere.

11. . Plants lose water through pores in their leaf surfaces
. Their pores open when it gets hot and they close when it is cool.
.transpiration can create a negative pressure that will move water and nutrients into the plants from the soil
. Mammals control their body temp. by releasing water through their skin pores in their sweat or perspiration
. Moisture is released to the atmosphere from breathing out from your lungs

12. . The moisture builds up in the atmosphere and forms clouds
. Clouds release water down to the Earth’s atmosphere