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Principles of Ecology: Matter, Energy, and Life. Chapter 2. Outline:. Food Webs Ecological Pyramids Biogeochemical Cycles. Sunlight. Solar energy that reaches the earth’s surface is in, or near, the visible light wavelengths. Drive photosynthesis.
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Outline: • Food Webs • Ecological Pyramids • Biogeochemical Cycles
Sunlight • Solar energy that reaches the earth’s surface is in, or near, the visible light wavelengths. • Drive photosynthesis. • More than half of the incoming sunlight may be reflected or absorbed by atmospheric clouds, dust, or gases. • Short wavelengths are filtered out by gases in the upper atmosphere.
Photosynthesis and Respiration • Photosynthesis • 6H2O + 6CO2 + sun C6H12O6 (sugar) + 6O2 • Cellular Respiration • C6H12O6+6O2 6H2O + 6CO2 + energy
Energy and Matter in the Environment • Species - All organisms genetically similar enough to breed and produce live, fertile offspring in nature. • Population - All members of a species that live in the same area at the same time. • Biological Community - All populations living and interacting in an area. • Ecosystem - A biological community and its physical environment ( water, mineral resources,air, sunlight etc.)
Much of ecology is concerned with understanding the ways energy and matter move through an ecosystem • In an ecosystem, there is interaction between the biotic and abiotic factors. • The study of an ecosystem involves how energy flows from one sytem to another. • An open ecosystem is a system in which animals can move from one area to another without a boundary (energy also moves) • A closed ecosytem does not allow cross over ( energy does not move)
Food Chains, Food webs & Trophic Levels • Photosynthesis provides all the energy for all ecosytems. • One of the major property of an ecosystem is productivity ( amount of biomass) in a given area in a given time. • Photosynthesis is called as the primary productivity in an ecosystem.
Food Webs and Trophic Levels • Productivity refers to the amount of biomass produced in a given or during a given time. • Primary Producers – organisms who photosynthesize e.g plants • Consumers – organisms who do not photosynthesize, they get their energy by eating other organisms. • Food Webs are series of interconnected food chains in an ecosystem.Some consumers feed on single sps., others have multiple food sources (Fig 2.13).
Trophic Levels • An organism’s feeding position in an ecosytem is called as trophic level. • Organisms can also be identified by the kinds of food they consume: • Herbivores – cows eat plants. • Carnivores – lion eat animals. • Omnivores - man eat plants and animals. • Detritivores – ants & beetles eat detritus ( litters) • Decomposers - bacteria and fungi breakdown complex organic matter into simpler compounds.
Note position of each organism in this food chain: • A corn plant ( primary producer) is eaten by a grasshopper ( primary consumer) • Chicken (secondary consumer )eats the grasshopper • Man ( tertiary consumer ) (top carnivore)eats the chicken • Fungi and bacteria ( decomposers) feed on dead decaying matter. • Energy is transferred from corn plants to man and when man dies, body decays and the decomposers break down complex compounds to simpler ones releasing the energy…food chain
Ecological Pyramids • Most ecosystems have huge number of primary producers supporting a smaller number of herbivores, supporting a smaller number of secondary consumers. • Second law of thermodynamics ( a certain amount of energy is lost / dissipated) • Ecosystems are not 100% efficient. • E.g A prairie dog when eating grasses does not digest all the plant parts efficiently. Moreover energy is also lost when he is running …moreso when a carnivore eats him…he does not eat the flesh completely..energy is lost in the ecosystem.
BIOGEOCHEMICAL CYCLES • Hydrological Cycle • Most of earth’s water is stored in the oceans, but solar energy continually evaporates this water, and winds distribute water vapor around the globe. • Water that condenses over land surfaces, in the form of rain, snow or fog supports all terrestrial ecosystem.
Living organisms emit the moisture to the atmosphere through respiration and perspiration. • Eventually this moisture re- enters the atmosphere or enters lakes and streams and ultimately to the oceans.
Carbon Cycle • Carbon serves a dual purpose for organisms: • Carbon is a structural component of organic molecules (C6H12O6, sugar) • Chemical bonds provide metabolic energy. • The carbon cycle begins with photosyntheric organisms that take up (CO2, carbon dioxide) to form starch. • Starch is taken up by several organisms, digested in stomach and simple sugars get broken down to simpler ones (CO2 ,H20 & energy).
Carbon cycle ( Contd.) • Sugar molecules either undergo respiration and releases carbon in the form of C02. • Simple sugar can also form large organic molecules such as cellular structrure of the cells. • When the body decay carbon returns to nature. • Dead decaying woods return their carbon after bacteria and fungi feed on them.
Fossil fuel (e.g coal and oil) , their carbon atoms are not retuned to soil until they are burnt. • Calcium carbonate (CaCO3) building structure for many coral reefs also contribute to the carbon cycle. • Limestones deposit in nature are biologically formed from CaC03.
The Nitrogen cycle • Several organic molecules contain nitrogen • Amino acids, peptides and proteins are large organic molecules that living organisms need for their existence. • Nitrogen is a very important nutrient for living things. • Nitrogen is a primary component of many household ( Ammonia and other detergents) and agriculture fertilizers.
Nitrogen Cycle ( Cont.) • Nitrogen makes up about 78% of the air, but plants cannot use N2, the stable diatomic molecule in air. • Plants acquire nitrogen through nitrogen cycle. • Nitrogen-fixing bacteria( live in roots of legumes) and blue-green algae) are highly organised to fix nitrogen of the atmosphere to Ammonia ( N2 to NH3) • They combine hydrogen of atmosphere with Nitrogen and form Ammonia( NH3)
The nitrogen cycle( Contd.) • Other forms of bacteria combine atmospheric oxygen ( O2) with Ammonia and form nitrites( NO2-). • Other forms of bacteria convert nitrites to nitrates (NO3-),which green plants can absorb and use. • After plants cells absorb nitrates, these nitrates are reduced to Ammonia (NH3). • Ammonia in plants are used to make amino acids which is used as building blocks to form protein( a polypetptide chain made up of several amino acids)
Nitogen cycle (cont.) • Nitrogen enters the environment in many ways: • Plants and animals die. • Fungi and bacteria decay dead organisms, releasing the ammonia which is converted back to nitrates. • Animals produce urine which is contain nitrogenous compounds. • Denitrifying bacteria breaks down nitrates to nitrogen ( N2) and nitrous oxide ( N2O), gases released to atmosphre.
Phosphorus Cycle • Abundant phosphorus stimulates plant and algal productivity. • Major component of water pollution. • Reduced levels of dissolved oxygen.
Sulphur Cycle • Sulphur is an essential component of proteins for living organisms. • Sulphur compounds determine the acidity of rainfall, surface water and soil. • Sulphur is tied up in soil as mineral rocks. • Weathering or emission from deep seafloor vent or volcanic eruption releases sulphur.
Sulfur Cycle • Sulfur compounds are important determinants of the acidity of water. • Particulates may also act as critical regulators of global climate. • Sulfur cycle is complicated by a large number of possible oxidation states. • Sulphur is oxidised to sulphur dioxide, sulphate or hydrogen sulphide.
Sulhur cycle Contd. • Human activities also releases a large quantity of sulphur, primarily through burning fossil fuels • Sulphur dioxide and sulphate causes human health problems. • When ocean water warms up, tiny organisms produces dimethylsulphide(DMS) which oxidises sulphur dioxide and then sulphate to the atmosphere.
Summary: • Food Webs • Ecological Pyramids • Biogeochemical Cycles