Cycles in Nature Biology The Cycles of Matter • Matter on Earth is limited so it gets used over and over again. • Each kind of matter has its own cycle. The Water Cycle – movement of water between the oceans, atmosphere, land and living things The Water Cycle • Sun causes evaporation (turns liquid water into gas/vapor) • During condensation, the water vapor cools and forms clouds. • The water that falls from the atmosphere to the land and oceans is called precipitation: rain, sleet, snow, hail. • Some of the precipitation that falls on land flows into streams, rivers, and lakes and is called runoff. • Some precipitation seeps into the ground and is stored between or in rocks: groundwater Water and Life • All living thing need water. • All living organisms are made up of mostly water. • Water does all of the following: – Transport nutrients and wastes in an organism – Regulate temperature All water taken in by an organism is returned to the environment. Plants release water vapor in a process called transpiration The Carbon Cycle – the exchange of carbon between the environment and living things The most common molecules in living things besides water are carbon containing molecules called organic molecules The Carbon Cycle • Photosynthesis is the basis of the carbon cycle. During photosynthesis, plants use carbon dioxide in the air to make sugars which in turn make energy for other animals that eat the plants. • Carbon returns to the environment when sugar molecules are broken down to release the energy in a process called respiration. During respiration, carbon dioxide and water are released. Decomposition and Combustion – Parts of the Carbon Cycle • Decomposition is the breaking down of substances into simpler molecules. • An example is when fungus or bacteria decompose dead organisms. • Combustion is the process of burning a substance, which also releases carbon dioxide into the atmosphere. • An example is burning wood or fuel. The Nitrogen Cycle – the movement of nitrogen between the environment and living things Nitrogen is important to all living things. They need nitrogen to build proteins and DNA for new cells. Converting Nitrogen Gas • 78% of the Earth’s atmosphere is nitrogen gas. • Most organisms cannot use nitrogen gas directly. But when bacteria in the soil change nitrogen gas into forms that plants can use, plants can get the nitrogen they need. This process is called nitrogen fixation. • Other organisms get the nitrogen by eating plants or eating other organisms that eat plants. • When organisms die, decomposers break down the remains and release nitrogen back into the soil. • Certain types of bacteria convert nitrogen in the soil back into gas which is returned to the atmosphere. Other cycles • Other forms of matter also pass through cycles. • Examples: calcium and phosphorus • Each of the cycles is connected. • Living organisms play a part in each of the cycles. Ecological Succession • A gradual development of a community over time is called succession. • Primary succession – when a small community starts to grow in an area where other organisms had not previously lived. There is no soil, just bare rock. Over a long period of time, organisms live and die on the rock and form soil. • The first organisms to live in the area are called pioneer species. Primary Succession Stages of Primary Succession • Secondary Succession - a community regrowing through a series of stages • Examples: – Fire or flood – Farming stops growing crops in an area Secondary Succession Primary vs. Secondary Succession Ecological Succession Yellowstone: • https://www.youtube.com/watch?v=AQQupO YonRo • Mt. St. Helens: • https://www.youtube.com/watch?v=BaRAGzjS kzo Mature Communities and Biodiversity • In early succession, only a few species grow in an area. • These grow quickly and make many seeds. • All species are vulnerable to disease, disturbance, and competition. • As a community matures, it may be dominated by a well adapted, slow-growing climax species. • As succession proceeds, more species become established. The variety of species that are present in an area is called biodiversity. • Communities with lots of biodiversity are less likely to be destroyed by plagues or diseases.
