Transcript Chapter 5:
Ecology How Ecosystems Work Where does energy come from? All energy in an ecosystem stems from the sun. Producers make this energy into useable energy for consumers. Producers • Makes own food (autotroph) • Photosynthesis: Carbon Dioxide + Water +Solar Energy = Sugar (carbohydrate)+ Oxygen Consumers Get energy from other organisms (heterotrophs) Types of consumers: • Herbivore • Carnivore • Omnivore • Decomposer • Cow, sheep, deer, grasshopper. • Lions, hawks, snakes, spiders. • Bears, pigs, humans. • Fungi, bacteria Exception to sun rule… Deep in oceans where the sunlight can not get, there are ecosystems around hydrothermal vents. Energy stems from bacteria that convert hydrogen sulfide into make their own food. Cellular Respiration • Used to get energy out of carbohydrates: Sugar + Oxygen = Carbon Dioxide + Water + Energy Sugar C6H12O6 + oxygen CO2 + H2O + Energy Transfer of Energy • Energy is transferred from one organism to another when one organism consumes another. • Each time energy is transfers it is called a trophic level. Trophic Levels can be expressed through food chains and food webs. Food Chain *A sequence in which energy is transferred from one organism to another. Food Web • Because most animals eat more than one type of food, a food web shows multiple chains linked together. Energy pyramid • The tree is the lowest trophic level and has the highest amount of energy. • Each increasing trophic level has less energy available to it due to loss of heat and other conversions. Trophic levels: • Ecosystems rarely have more than 4-5 trophic levels because there simply is not enough energy to support higher levels. The Cycling of Materials In an ecosystem materials are constantly reused. • The Carbon cycle • The Nitrogen cycle • The Phosphorus cycle The Carbon Cycle • Carbon is an essential component of proteins, fats, and carbohydrates which make up all organisms. The Carbon Cycle Carbon is cycled between: • Land-limestone & fossil fuels • Atmosphere-Carbon dioxide • Water-Dissolved with in • Organisms-protein, fats, carbohydrates & bones/shells Fossil Fuels • Left over stored carbon from bodies of dead organisms from millions of years ago. • Burning of fossil fuels along with natural burning of wood or forests = 6 billion metric tons of CO2 • Half of this stays in the atmosphere, causes global warming The Nitrogen Cycle • Organisms use nitrogen to build proteins to build new cells. • 78% of the gases in the atmosphere. • Most organisms cannot use atmospheric Nitrogen. Nitrogen Fixing Bacteria •Fix atmospheric nitrogen into chemical compounds •Roots of legumes or in soil Decomposing Bacteria • Break down the wastes of animals, leaves and other decaying organisms to return the Nitrogen to the soil. • Bacteria break some of the nitrogen into nitrogen gas The Nitrogen Cycle Nitrogen cycles by… • Atmosphere-Nitrogen gas •Bacteria-Nitrogen fixing and decomposing The Phosphorus Cycle • Phosphorus is an essential element for bones and teeth in animals. • This cycle is slow and does not normally occur in the atmosphere because Phosphorus does not normally occur as a gas. The Phosphorus Cycle Phosphorus cycles… • Earth-soil, rock, fertilizers • Water-sinks to bottom • Decomposition of plants and animals Fertilizers • Fertilizers contain nitrogen and phosphorus to help stimulate rapid growth and bigger plants. • Excess can enter terrestrial and aquatic ecosystems leading to rapid growth of algal blooms. Algae can deplete oxygen available to fish and other aquatic life. Acid Precipitation • Burning coal, wood, or oil releases nitric oxide • Combines with oxygen and water vapor to make nitric acid (dissolves in rain & snow) How Ecosystems Change • Ecological succession –Primary succession. –Secondary succession. –Old-field succession. Ecological Succession • Gradual process of change and replacement of the types of species in a community. • May take hundreds or thousands of years. Primary Succession • Occurs on a surface where no ecosystem existed before. –Rocks, cliffs, and sand dunes Secondary Succession • Occurs in ecosystems that have been disturbed by humans, animals, or natural processes such as storms, floods, earth, quakes, and volcanos. Pioneer Species • The first organisms to colonize a newly available area and begin the process of ecological succession. • Make it more habitable for other species to move in. Climax Community • A final stable community. • Still will continue to change in small ways over time. Old-field Succession • Occurs when farm land is abandoned. –Grass/weeds (w/in 1 year) –Perennial plants/grasses (w/in 2 years) –Shrubs (w/in 3-10 years) –Pine forest (about year 20) –Oak forest (about 150 years) Succession • Primary succession takes much longer than secondary succession. –Pioneer species generally tends to be lichens that break down the rocks (can live without soil). Mosses may then grow, etc. starting the succession process.