Cycling maintains homeostasis (balance) in the environment. Nutrient Cycles Cycling maintains homeostasis (balance) in the environment. 3 cycles to investigate: 1. Water cycle 2. Carbon cycle 3. Nitrogen cycle

Water cycle- Evaporation- is a type of vaporization of a liquid to gas phase from the surface of a liquid. Transpiration- evaporation of water from plant leaves. (diagram on next page) Condensation- change of the physical state of matter from gas phase into liquid phase, and is the reverse of evaporation. Precipitation- any product of the condensation of atmospheric water vapor that falls under gravity.

Water cycle-

Carbon cycle- Photosynthesis and respiration cycle carbon and oxygen through the environment.

The chemical equation for photosynthesis is: 6CO2 + 6H2O ------> C6H12O6 + 6O2 Sunlight energy CO2 = carbon dioxide H2O = water Light energy is required C6H12O6 = glucose O2 = oxygen The chemical equation for respiration is: C6H12O6 + 6O2 6CO2 + 6H2O Glucose + Oxygen Carbon Dioxide + Water

Carbon cycle-

Nitrogen cycle- Atmospheric nitrogen (N2) makes up nearly 78%-80% of air. Organisms can not use it in that form. Lightning and bacteria convert nitrogen into usable forms.

Nitrogen-fixing bacteria: rhizobacteria Nitrogen cycle- Nitrogen-fixing bacteria: rhizobacteria Some live in a symbiotic relationship with plants of the legume family (e.g.,alfalfa soybeans, clover, peas, peanuts).

Nitrogen cycle- Some nitrogen-fixing bacteria live free in the soil. Nitrogen-fixing bacteria: cyanobacteria are essential to maintaining the fertility of semi-aquatic environments like rice paddies.

Nitrogen cycle- Only in certain bacteria and industrial technologies can fix nitrogen. Nitrogen fixation-convert atmospheric nitrogen (N2) into ammonium (NH4+) which can be used to make organic compounds like amino acids. N2 NH4+

Nitrogen Cycle Atmospheric nitrogen Lightning Denitrification by bacteria Animals Nitrogen fixing bacteria Plants Decomposers Nitrification by bacteria Nitrites Nitrates Ammonium

This is called biological magnification Toxins in food chains- While energy decreases as it moves up the food chain, toxins increase in potency. This is called biological magnification Ex: DDT & Bald Eagles