Unit B: Systems and Interactions in Nature Chapter 1 – Cycles in Nature

The Nitrogen Cycle All living things need nitrogen to survive, but most organism’s cannot use nitrogen in its atmospheric form. In the nitrogen cycle, nitrogen has is changed into forms that plants can use. Nitrates and ammonia

The Nitrogen Cycle How nitrogen is changed Most of the nitrogen gas is changed by bacteria in the soil or in nodules on the roots of some plants. Some nitrogen gas is changed by lightning.

The Nitrogen Cycle How nitrogen is used Plants use nitrogen in the soil to make proteins. Animals get nitrogen by eating plants, or by eating other animals that eat plants.

The Nitrogen Cycle How nitrogen is returned to soil Through animal wastes: Solid waste contains nitrates Liquid waste contains ammonia When animals and plants die, bacteria releases nitrates and ammonia through decomposition

The Carbon Dioxide-Oxygen Cycle Carbon and oxygen is moved among plants, animals, and the environment. All living organisms are involved in this cycle.

Carbon Dioxide-Oxygen First, photosynthesis occurs: Plants on land and in the water make their own food by changing the sun’s energy into food and taking in carbon dioxide from air and water Oxygen is released into the air and water

Carbon Dioxide-Oxygen All living organisms use the oxygen that was released for respiration (breathing). They release carbon dioxide back into the atmosphere.

Carbon Dioxide-Oxygen Carbon is also returned into the cycle when organisms die. Some carbon is stored in the body until decomposition occurs and is used for food by plants and animals. The rest is released as carbon dioxide into the air.

Carbon Dioxide-Oxygen The carbon dioxide in the air is then taken in again for the process of photosynthesis, starting the process over. The carbon underground could be turned into fossil fuels. The fossil fuels are then burned (combustion) and carbon dioxide is returned into the air.

Changing the Balance The carbon dioxide-oxygen cycle was in balance for millions of years, but human influence has greatly impacted the cycle. Our industrial activity releases excess amounts of carbon dioxide into the atmosphere. Forests are cut down to meet other human needs (shelter, farms, etc.). There is a shortage of trees, so the excess of CO2 is building up in the air. Too much CO2 is poisonous to animals and people.

Unit B: Systems and Interactions in Nature Chapter 1 – The Water Cycle

Water All living organisms need water to survive. Plants take in water from the soil. Most animals drink water from lakes or streams. About 75% of Earth’s surface is water. About 70% of the human body is water.

The Water Cycle Water moves through the environment through the water cycle.

Evaporation The heat of the sun changes water on Earth’s surface into water vapor

Condensation The higher up the water vapor goes, the cooler the air gets. The water vapor changes back into a liquid, forming a cloud.

Precipitation Once many droplets join together to form clouds, the water may fall back to Earth. Rain, snow, hail, sleet

Transpiration This is the process where plants and animals put water back into the atmosphere. Plants give off water through their stomata. Animals release water vapor when they exhale. Animals also release water through their urine.

Water Use All of the water on Earth today is the same water that was here billions of years ago. However, human activity contaminates the water with chemicals such as oil and road salt.

How can we conserve and preserve our fresh water supply?