How do natural cycles affect ecosystems? Chapter 3 lesson 2

Earth’s Cycles The Water Cycle: The sun’s energy causes water to evaporate from Earth’s surface and form clouds. Then gravity causes precipitation to fall to Earth and the cycle begins again. 1. Evaporation 2. Condensation 3. Precipitation

Succession- is the gradual long-term change of species in an ecosystem. Ecosystems go through cycles called succession. There are two major types of succession – primary and secondary.

Primary succession occurs when plants first take root in an area that has no plants. This could happen after a volcanic eruption covers an area with lava. The first plants that grow would begin the process of primary succession.

Secondary succession takes place when most, but not all, vegetation in an area has been removed. There are some plants and soil on which new plants can grow. For instance, a farmer could cut down trees to plant a cornfield.

There is a limited supply of Carbon on Earth There is a limited supply of Carbon on Earth. But it never runs out because it is constantly recycled in the Carbon Cycle. 1.Plants use carbon dioxide during photosynthesis from the air, water from the soil, and energy from the sun. 2. The plant can use the food or store it as starch. As a result of photosynthesis, oxygen is released into the air. Humans breathe in the oxygen and exhale carbon dioxide. 3. When the plants die, they break down and decompose into the soil. 4. The carbon re-enters the soil, is compressed for thousands of years and can become fossil fuels. 5. When humans use (burn) these fuels, ie coal, carbon dioxide re-enters the atmosphere. The carbon cycle is the movement through Earth’s ecosystems of carbon as solids, liquids, or gases. Respiration- the process of cycling carbon from living things back into the air and water.

The Nitrogen Cycle The movement of nitrogen in different forms from living organisms to the nonliving part of the environment and back About 78% of the gas in Earth’s atmosphere is nitrogen. However, most organisms can’t use nitrogen gas straight from the air. So an important part of the nitrogen cycle is the changing of nitrogen into a form that plants can use. This is called nitrogen fixation. Nitrogen can be “fixed” by bacteria in plants and soil or as the result of lightning strikes. *Images provided by Google and AltaVista