Natural Cycles

The cycles of matter Imagine an aquarium containing water, fish, snails, plants, algae, and bacteria. The tank is sealed so tight that only light can enter. Food, water, and air cannot be added. Will the organisms in this environment survive? Through photosynthesis, plants and algae make their own food. They also supply oxygen to the tank. Wastes from fish and snails fertilize the plants and algae. Fish and snails take in oxygen and eat plants and algae. Organisms that die are decomposed by the bacteria. They can survive because the materials are being recycled!

The cycles of matter Earth’s biosphere also contains a fixed amount of water, carbon, nitrogen, oxygen, and other materials required for life. These materials are constantly cycled through the environment to be used over and over again.

Cycles in Nature The water cycle The carbon-oxygen cycle The nitrogen cycle

Water cycle the movement of water on, in, and above the earth. Water is always changing state and moving from one place to another.

Where is water found? Living things – very little trapped here Oceans, rivers, lakes – substantial percentage Atmosphere – water vapor Groundwater – soaked under the ground

Water Cycle evaporation – sun changes water from liquid to gas The sun heats up water in rivers, streams, oceans, and lakes and turns it into vapor or steam. This water vapor rises into the air.

Water Cycle transpiration – water is evaporated from plant pores

Water Cycle condensation – water changes from a gas to a liquid Water vapor cools down and changes back into liquid water droplets. These droplets clump together to form clouds.

Water Cycle precipitation – water that falls from the atmosphere to the land or ocean (rain, sleet, hail, snow) When the water droplets in clouds become large and heavy enough, they fall to the Earth.

Water Cycle Some of the precipitation that falls on land flows into streams, rivers, and lakes and is known as runoff. Other precipitation is absorbed into the ground and is stored as groundwater. This water will slowly flow back into the soil, streams, rivers and oceans.

Water Cycle

The carbon-oxygen cycle

The carbon-oxygen cycle photosynthesis – plants take in carbon-dioxide and give off oxygen

The carbon-oxygen cycle respiration – animals take in oxygen and give off carbon-dioxide CARBON- DIOXIDE OXYGEN

The carbon-oxygen cycle decomposition – fungi and bacteria break down matter which produces carbon-dioxide

The carbon-oxygen cycle combustion – burning wood or fossil fuels which give off carbon-dioxide.

The carbon-oxygen cycle Photosynthesis Respiration Decomposition Combustion Carbon-dioxide Carbon-dioxide Carbon-dioxide Do you see a problem?

The Nitrogen Cycle 78% of the air we breathe is made of nitrogen gas. Even though this gas is all around us, we and other organisms can’t use it. In the nitrogen cycle, nitrogen gas is converted into other forms and back to gas again. N₂

The Nitrogen Cycle

Nitrogen-fixing bacteria The Nitrogen Cycle nitrogen fixation – changing nitrogen gas into forms that plants can use. Nitrogen-fixing bacteria Lightning

REVIEW In the nitrogen cycle, __________________ will change nitrogen in the air into nitrates that plants can use. In the nitrogen cycle, _________________________ will change nitrogen in the ground into nitrates that the plants roots can take in and use. In the carbon-oxygen cycle, plants take in ___________________ and release or give off ___________________________. In the carbon-oxygen cycle, animals breath in ______________________ and release ___________________.