1. Components of the Water Cycle
________________: when liquid water changes into water vapor and enters the atmosphere
________________: the process of changing water from a gas to a liquid
________________: when water drops become large enough and fall to the ground as rain, snow, sleet, etc.
________________: Transpiration is the process by which plants lose water out of their leaves.  Transpiration gives evaporation a bit of a hand in getting the water vapor back up into the air.

2. Carbon Cycle
How carbon molecules move between the living and nonliving world
The __________carbon atoms in your body today have been used in countless other molecules since time began.
Plants __________ carbon dioxide from the ___________ and use it, combined with water they get from the soil, to make the substances they need for _________.

3. Carbon Cycle (cont.)
Animals, like a rabbit, eat the plants and use the carbon to build their own tissues.
Other animals, such as the fox, eat the rabbit and then use the carbon for their own needs.
These animals _________ carbon dioxide into the air when they ________, and when they _________, since the carbon is returned to the soil during decomposition.

4. Carbon cycle (cont.)
The carbon atoms in soil may then be used in a new plant or small microorganisms.
Ultimately, the __________ carbon atom can move through many organisms and even end in the same place where it began.

5. Nitrogen Cycle
The __________ of nitrogen from the atmosphere to the soil, to living organisms, and back to the atmosphere
The growth of all organisms depends on the availability of mineral nutrients, and none is more important than ___________, which is required in large amounts as an essential component of____________, _____________and other cellular constituents.

6. Nitrogen Cycle (cont.)
There is an abundant supply of nitrogen in the earth's atmosphere - nearly _______in the form of N2 gas. However, N2 is unavailable for use by most organisms because there is a triple bond between the two nitrogen atoms, making the molecule almost _____________.

7. Nitrogen Fixation
In order for nitrogen to be used for growth it must be "fixed" (combined) in the form of ammonium (NH3) or nitrate (NO3) ions.
some bacteria can convert N2 into ammonia by the process termed _________________; these bacteria are either free-living or form symbiotic associations with plants or other organisms (e.g. termites, protozoa)
Nitrogen-fixing bacteria can be found in the _________ as well as on submerged objects in lakes and ponds. These are called cyanophytes (blue-green algae).

8. Legume symbioses
The most familiar examples of nitrogen-fixing symbioses are the ___________________(peas, beans, clover, etc.).

9. Other nitrogen
______________ replace nitrogen in the soil by ___________ nitrogen-fixing _________ or using _____________ that contain nitrogen compounds that plants need for growth.

10. More ammonia
A small amount of nitrogen fixation also results from the passage of ultraviolet light and _______________through the air, causing nitrogen to react with oxygen to form nitrate ions.
Additional amounts of nitrate and ammonia are put into the atmosphere by ____________, by combustion of fossil fuels, and by forest fires.

11. Ammonification
At any one time a large proportion of the total fixed nitrogen will be locked up in the _____________ or in the dead remains of organisms.
The ______________ of animals and dead bodies are broken down in the soil by decomposers
This produces ammonia.

12. Nitrification
Some bacteria called nitrifying bacteria take the ammonia and change it to a nitrite ion, and then a different group of nitrifying bacteria change that nitrite ion to a nitrate ion.
This then can be taken up _____________of the plant and be used.

13. Problems of nitrification
The ammonium ion is readily adsorbed onto the clay soil and soil organic matter, preventing it from being _______________of the soil by rainfall.
In contrast, the nitrate ion is not held on soil particles and so can be washed down the soil - the process termed _________________
in this way, valuable nitrogen can be lost from the soil, reducing the soil fertility.

14. The problems with too many nitrates
The nitrates can then _______________ in groundwater, and ultimately in drinking water.
There are strict regulations governing the amount of nitrate that can be present in drinking water, because nitrates can be changed to nitrites by microorganisms in the gut.
Nitrites are absorbed from the gut and bind to haemoglobin in your blood, _____________ its oxygen-carrying capacity.

15. Denitrification
If the soil becomes too compacted or gets too wet, air cannot penetrate.
This allows bacteria called denitrifying bacteria to _____________ nitrate to nitrous oxide or nitrogen gas which is then lost to the atmosphere.
That is why it is important for farmland to be kept ________________________.