Ecology Unit

Standards Based Objectives

Mr. Walker BHS

Objective 1: Describe the water, carbon, and nitrogen cycles�

• Students should be able to:
• Describe the parts of the water cycle
• Explain how carbon is used and produced by organisms.
• Explain how carbon is stored on Earth
• Describe the importance of nitrogen fixing bacteria

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Objective 1: Describe the water, carbon, and nitrogen cycles

• Evaporation: is the process by which water changes from a liquid to a gas or vapor.
• Sublimation: is the conversion between the solid and the gaseous phases of matter, with no intermediate liquid stage
• Precipitation: is water released from clouds in the form of rain, freezing rain, sleet, snow, or hail. 
• Transpiration: is the process by which moisture is carried through plants from roots to small pores on the underside of leaves, where it changes to vapor and is released to the atmosphere. 
• Condensation: is the process by which water vapor in the air is changed into liquid water. 

Summary: Nitrogen Cycle

• Nitrogen is everywhere! In fact, the gas makes up about 78% of Earth's atmosphere by volume, far surpassing the oxygen, O, we often think of as "air".
• But having nitrogen around and being able to make use of it are two different things. Your body, and the bodies of other plants and animals, have no good way to convert N₂ into a usable form. We animals—and our plant compatriots—just don't have the right enzymes to capture, or fix, atmospheric nitrogen.
• Still, your DNA and proteins contain quite a bit of nitrogen. Where does that nitrogen come from? In the natural world, it comes from bacteria!
• Bacteria play a key role in the nitrogen cycle.
• Nitrogen enters the living world by way of bacteria and other single-celled prokaryotes, which convert atmospheric nitrogen (N₂) into biologically usable forms in a process called nitrogen fixation. Some species of nitrogen-fixing bacteria are free-living in soil or water, while others are beneficial symbionts that live inside of plants.
• Nitrogen-fixing microorganisms capture atmospheric nitrogen by converting it to ammonia (NH₃)which can be taken up by plants and used to make organic molecules. The nitrogen-containing molecules are passed to animals when the plants are eaten. They may be incorporated into the animal's body or broken down and excreted as waste, such as the urea found in urine.
• Nitrogen doesn't remain forever in the bodies of living organisms. Instead, it's converted from organic nitrogen back into N₂ gas by bacteria (denitrification). This process often involves several steps in terrestrial—land—ecosystems. Nitrogenous compounds from dead organisms or wastes are converted into ammonia—NH₃ by bacteria (ammonification), and the ammonia is converted into nitrites (NO₂) and nitrates (NO₃). This is nitrification. In the end, the nitrates (NO₃) are made into N₂ as by denitrifying prokaryotes.

Nitrogen Cycle

• Nitrogen fixation: is a process by which atmospheric nitrogen (N₂) is converted into ammonium (NH4) which can be used by plants.�Ammonification: When an organism excretes waste or dies, the nitrogen in its tissues is in the form of organic nitrogen (e.g. amino acids, DNA). Various fungi and prokaryotes then decompose the tissue and release inorganic nitrogen back into the ecosystem as ammonia. This is ammonification.
• Nitrification: is the biological oxidation of ammonia (NH₃₎ to nitrite (NO₂) followed by the oxidation of the nitrite (NO₂) to nitrate (NO3). 
• Denitrification: A bacteria facilitated process where nitrate (NO3) is reduced and ultimately produces atmospheric nitrogen (N₂).

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Carbon Cycle Summary

• Carbon: building block and fuel source
• About 18% of your body consists of carbon atoms, by mass, and those carbon atoms are pretty key to your existence! Without carbon, you wouldn't have the plasma membranes of your cells, the sugar molecules you use for fuel, or even the DNA that carries instructions to build and run your body.
• Carbon is part of our bodies, but it's also part of our modern-day industries. Carbon compounds from long-ago plants and algae make up the fossil fuels, such as coal and natural gas, that we use today as energy sources. When these fossil fuels are burned, carbon dioxide— CO₂ is released into the air, leading to higher and higher levels of atmospheric CO₂. This increase in CO₂ affects Earth's climate and is a major environmental concern worldwide.
• Let's take a look at the carbon cycle and see how atmospheric CO₂ and carbon use by living organisms fit into the bigger picture of carbon cycling.

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• The carbon cycle
• The carbon cycle is most easily studied as two interconnected subcycles:
• One dealing with rapid carbon exchange among living organisms
• One dealing with long-term cycling of carbon through geologic processes
• Although we will look at them separately, it's important to realize these cycles are linked. For instance, the same pools of atmospheric and oceanic CO₂ that are utilized by organisms are also fed and depleted by geological processes.
• As a brief overview, carbon exists in the air largely as carbon dioxide—CO₂—gas, which dissolves in water and reacts with water molecules to produce bicarbonate—HCO₃. Photosynthesis by land plants, bacteria, and algae converts carbon dioxide or bicarbonate into organic molecules. Organic molecules made by photosynthesizers are passed through food chains, and cellular respiration converts the organic carbon back into carbon dioxide gas.
• Long-term storage of organic carbon occurs when matter from living organisms is buried deep underground or sinks to the bottom of the ocean and forms sedimentary rock. Volcanic activity and, more recently, human burning of fossil fuels bring this stored carbon back into the carbon cycle. Although the formation of fossil fuels happens on a slow, geologic timescale, human release of the carbon they contain—CO₂—is on a very fast timescale.

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The biological carbon cycle

• Carbon enters all food webs, both terrestrial and aquatic, through autotrophs, or self-feeders. Almost all of these autotrophs are photosynthesizers, such as plants or algae.
• Autotrophs capture carbon dioxide from the air or bicarbonate ions from the water and use them to make organic compounds such as glucose. Heterotrophs, or other-feeders, such as humans, consume the organic molecules, and the organic carbon is passed through food chains and webs.
• How does carbon cycle back to the atmosphere or ocean?
• To release the energy stored in carbon-containing molecules, such as sugars, autotrophs and heterotrophs break these molecules down in a process called cellular respiration. In this process, the carbons of the molecule are released as carbon dioxide. Decomposers also release organic compounds and carbon dioxide when they break down dead organisms and waste products.

The geological carbon cycle

• The geological pathway of the carbon cycle takes much longer than the biological pathway described above. In fact, it usually takes millions of years for carbon to cycle through the geological pathway. Carbon may be stored for long periods of time in the atmosphere, bodies of liquid water—mostly oceans— ocean sediment, soil, rocks, fossil fuels, and Earth’s interior.
• The level of carbon dioxide in the atmosphere is influenced by the reservoir of carbon in the oceans and vice versa. When the organisms die, their remains may sink and eventually become part of the sediment on the ocean floor. Over geologic time, the sediment turns into limestone, which is the largest carbon reservoir on Earth.
• On land, carbon is stored in soil as organic carbon from the decomposition of living organisms or as inorganic carbon from weathering of terrestrial rock and minerals. Deeper under the ground are fossil fuels such as oil, coal, and natural gas, which are the remains of plants decomposed under anaerobic—oxygen-free—conditions. Fossil fuels take millions of years to form. When humans burn them, carbon is released into the atmosphere as carbon dioxide.
• Another way for carbon to enter the atmosphere is by the eruption of volcanoes. Carbon-containing sediments in the ocean floor are taken deep within the Earth in a process called subduction, in which one tectonic plate moves under another. This process forms carbon dioxide, which can be released into the atmosphere by volcanic eruptions or hydrothermal vents.

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Carbon Cycle

Succession of Ecosystems

• -Succession: A regular pattern of changes over time in the types of species in a community. Can take hundreds of thousands of years.
• -Climax Community: The community that eventually forms if the land is left undisturbed.
• -Primary Succession: Succession which occurred on surfaces where no ecosystem existed before.
• -Secondary Succession: Succession which occurs on a surface where an ecosystem has previously existed.
• -Pioneer Species: The first organisms to colonize any newly available area and start the process of succession.
• -Soil: Forms from broken down rock, decayed organisms, water, and air

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