Science NotesChapter 21 Energy Flow in Ecosystem.docx.docx



Science Notes - Chapter 21Section 1:Energy Flow in EcosystemsEnergy Roles:Each of the organisms in an ecosystem fills one of the energy roles of: producer, consumer, or decomposer.Producers:*Organism makes its own food*Source of all food in ecosystem*A few ecosystems originally obtain energy from a source other than sunlight- this ecosystem is found in rocks deep in the earth, gets energy from hydrogen sulfide that is found in their environmentConsumers:*organism that obtains energy by feeding on other organism*classified by what they eat -Herbivore – consumer that eats only plants-Carnivore - consumer that eats only animals – Some are scavengers that feed on the bodies of dead animals-Omnivore – consumers that eat plants and animalsDecomposers:*break down waste and dead organisms and return the raw materials to the ecosystem*known as nature’s recyclers*mushrooms and bacteria are decomposersFood Chains and Food Webs:*Energy enters the ecosystem as sunlight and is converted into food molecules by the producers*Shows the movement of energy through an ecosystem. This can be shown in the diagrams called food chains and food webs.Food Chain:*a series of events in which one organism eats another and obtains energy -First organism in food chain is the producer -Second organism feeds on (or off of) the producer and is called the first level consumer -The Second level consumer eats the first level consumer**Food chains show only one possible path, along which energy can move through the ecosystems.Food Webs:*consist of many overlapping food chains. Can show multiple ways in which consumers interact. Energy Pyramids*When an organism in an ecosystem eats, it obtains energy. (The energy comes from the food.)*The energy pyramid shows the amount of energy that moves from one feeding level to the next.*The most energy is available at the producer level of the pyramid. As you move up the pyramid each level has less energy available than the level below it!!!*Only about 10% of the energy at one level of a food web is transferred to the next higher level. The other 90% of the energy is lost at each step (up on the pyramid) because of this there is not enough energy to support many feeding levels in an ecosystem.*Organism at higher food levels don’t necessarily require less energy to live than lower levels. Since so much is lost, the amount of energy at producer level limits the # of consumers that it can support. This is why there are fewer animals at top of the pyramid. Section 2:Cycles of Matter* Water cycle- the continuous process by which water moves from Earth’s surface to the atmosphere and back.- Evaporation, condensation and precipitation make up the water cycle. *Evaporation – the process by which molecules of liquid water absorb energy and change to a gas. - Liquid evaporates from oceans, lakes and living things that give off water and forms a water vapor (a gas).- Energy for evaporation comes from the heat of the sun.*Condensation – the process by which a gas changes to a liquid.- As the water vapor rises in the atmosphere, it cools down. - Cool vapor turns back into tiny drops of liquid water. This is the process of condensation.- This water vapor collects around particles of dust and forms clouds * Precipitation – when water vapor condenses the drops of water in the cloud grow larger, eventually the heavy drops will fall from the cloud resulting in rain, sleet, hail or snow. -Most precipitation falls back into the oceans or lakes.The Carbon and Oxygen Cycles- Producers, consumers and decomposers play roles in recycling carbon and oxygen.- Producers take in carbon dioxide gas from the air during photosynthesis.- They use the carbon to make food (sugars and starches) - Consumers break down carbon (sugars) to obtain energy and release CO2.- When producers and consumers die, decomposers break down their remains and return the carbon to the soil.- Producers release oxygen as a result of photosynthesis- Most organisms take in O2 from the air or water and use it to carry out life processes. The Nitrogen Cycle- Nitrogen moves from the air to the soil, into living things and back into the air.- Our atmosphere is 78 % Nitrogen gas (free nitrogen-not combined with other kinds of atoms). Most organisms cannot use it in this form.- Most organisms can use it when it is “fixed” or combined with other elements (nitrogen-containing compounds)- Nitrogen fixation the process of changing free nitrogen into a usable form.Returning Nitrogen to Environment- Once nitrogen is fixed, consumers can use it to make proteins.- Decomposers break down these complex compounds in animal wastes and dead organisms. Decomposition returns simple nitrogen compounds to the soil. - Nitrogen can cycle from the soil to producers, then to consumers many times.- Eventually, bacteria break down nitrogen compounds completely and release “free” nitrogen back into the air. ................
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