ࡱ> |~{[ 0bjbj~~ *bbb(*****>>>>$b>wj.# iiiiiii$!lnlj*///j**1j/R**i/i j\ RiPu2fiGj0wj2g Co'CoRiCo*Ri///////jj///wj////Co/////////B :  Ecosystems Ecosystem Approach to Ecology Trophic Relationships Trophic levels based on how organism gets food Primary Producers (autotrophs) convert inorganic energy into organic energy (IB 54.1) Heterotrophs obtain organic energy by consuming other organisms (IB 54.1) Primary Consumer Secondary consumer Tertiary consumer Detritivores organisms that feed on dead organic matter (detritus) by ingesting it. (IB 54.1) Saprotrophs organisms that feed on dead organic matter (detritus) by secreting digestive enzymes into the detritus and absorbing the nutrients. (IB 54.1) Decomposition connects all trophic levels Energy can enter and leave an ecosystem but nutrients must be recycled. (IB 54.5) Mainly done by bacteria and fungi Release nutrients back to environment Decomposers break down detritus and release organic and inorganic substances into the environment (soil, water, air, etc). The substances are then taken up by autotrophs, which in turn are eaten by heterotrophs. Decomposers (mainly detritivores) break down detritus and are then eaten by consumers. Saprotrophic bacteria and fungi commonly release inorganic substances back into the environment for use by autotrophs. However, some organisms will directly consume the bacteria and fungi to get organic nutrients. (IB 54.7) Laws of Physics and Chemistry Law of Conservation of Energy energy is not created or destroyed, only transferred. Energy of the universe is constant (IB 54.5) Law of conservation of mass mass is not created or destroyed, only transformed. (IB 54.5) Most energy can be traced back to Sun Primary Production The amount of light energy converted to chemical energy by autotrophs Energy Budget Photosynthetic production sets the limit of energy in an ecosystem Not all solar energy reaches the surface Of that, most of the solar energy is absorbed and reflected by the surface So, only a little energy actually reaches the photosynthetic organisms Of this, only 1% is converted to chemical energy Gross-Primary Production amt of energy converted to chemical energy per unit time. (IB 54.11) Net-Primary Production = GPP energy used by autotrophs for respiration (IB 54.11 and 54.12) NPP is the amt of energy available to consumers Primary production is expressed as E/unit area/unit time (J/m2/yr) or as biomass of vegetation added per unit area per unit time (g/m2/yr) Biomass the dry weight of organic matter in a group of organisms in a particular habitat. (IB 54.11) Standing Crop vs. primary production Tropics are the most productive terrestrial ecosystems Estuaries and Coral reefs are very productive Open ocean contributes more primary production than any other ecosystem Aquatic Ecosystems and Limiting Factors Light limits production More than half is absorbed in 1st meter of water. However, light is not the only limiting factor Nutrients are the primary limiting factors Limiting Nutrient what must be added to an increase in production Nitrogen and Phosphorus are the most common Nitrogen is usually the limiting factor in marine waters Phosphorous is usually the limiting factor in fresh waters Sometimes other elements are the limiting factors (iron) Marine waters that have great upwelling (overturning) are generally not limited by nutrients For freshwater, if too much of the limiting nutrient is added, eutrophication can occur Terrestrial Ecosystems Temperature and moisture are usually the limiting factors Nutrients play a role on the local scale Usually nitrogen and phosphorus Secondary Production The amt of chemical energy that is converted to consumers biomass Efficiency of Energy Transfer Not all of the energy obtained from food is used by the organism; organisms are not 100% efficient (IB 54.3) Energy losses between trophic levels include material not consumed, material not assimilated, and heat loss through cell respiration. (IB 54.2) Production Efficiency the fraction of food energy not used for respiration and not passed out through feces Birds and mammals range from 1-3% Fish average about 10% Insects average about 40% Trophic efficiency - % of production transferred between trophic levels For all organisms, the avg is about 10% (IB 54.3) Represented by energy pyramids The energy lost through the trophic levels limit the biomass of each trophic level This is why most food webs only have 4 or 5 trophic levels As a result, predators are at greatest risk of becoming extinct Animals that are omnivores have a greater chance of survival Green World Hypothesis Herbivores dont eat all the vegetation because of limiting factors plants have defenses nutrients abiotic factors competition interactions The Cycling of Chemical Elements Chemical elements are limited Decomposition redistributes the elements Called Biogeochemical cycles Biological and Geological Processes Cycles of gaseous forms of C, O, S, and N occur in the atmosphere and are global Cycles of P, K, Ca and trace elements occur more in the soil and are more local Refer to Figure 54.15 on p. 1209 for a general model of elements Water doesnt really fit in the general model. It is more of a physical process than chemical. The Nitrogen Cycle Atmosphere is made of 80% nitrogen but it is mostly in the form of N2 2 possible ways to enter an ecosystem Atmosphere Deposition (5-10%) NH4+ and NO3- Dissolved in precipitation Nitrogen Fixation done by prokaryotes (symbiotic and nonsymbiotic) converts N2 to usable nitrogen releases excess ammonia Most of the NH3 in the soil is converted by aerobic bacteria into nitrites and then nitrates Nitrification Nitrates are then absorbed by plants and are used to make amino acids Animals can only receive nitrogen by eating plants or other animals Some anaerobic bacteria will convert nitrates back to N2 - Denitrification Bacterial and Fungal decomposers can convert organic N back to ammonium Ammonification The majority of N is recycled locally by decomposition and reassimilation C. The Phosphorus Cycle Phosphorus is needed for production plasma membranes, nucleic acids, ATP, etc. Does not involve movement within the atmosphere because there are no P gases Phosphorous is usually obtained in the form of phosphate. Weathering rocks add phosphates to the soil Plants then absorb the phosphates to make organic compounds. Consumers receive phosphates by eating plants and/or animals. Phosphates are then returned to the soil by feces and decomposition of dead organisms It is generally localized in the soil because soil particle tend to bind to the phosphate Phosphate can leach into water tables The Carbon Cycle Carbon is needed because it is the basic building block of all life. Exists as carbon dioxide in the atmosphere Photosynthetic organisms absorb CO2 to make organic food It is then passed to consumers through the trophic levels Consumers and detritivores return the carbon to the atmosphere by cellular respiration Humans add to this by burning fossil fuels Decomposition Rates Determine the rates of recycling Tropics decomposes in a few month to years Temperate decomposes in 4-6 years Tundra decomposes in about 50 years Temperature, water, and oxygen determine the rates of decomposition Human Impact on Ecosystems Human Population & Chemical Cycles We remove nutrients from area and move them to another area Leads to depletion and excess of nutrients Farmland eventually becomes depleted of nutrients Fertilizers must then be used Agriculture has a great impact on the N cycle plowing mixes the soil and provides oxygen to increase decomposition removing plants causes N to leach from the ecosystem the excess of free N contribute to global warming and acid rain Ecosystems have a critical load for N the amt of N that can be added to the ecosystem without damaging it. As N leaches from the ground to water, eutrophication often results Acid Precipitation Defined as rain, snow, or fog that has a pH less than 5.6 Results from the release of sulfur and nitrogen when burning fossil fuels S and N react with atmospheric water to make sulfur oxides and nitrogen oxides Lowers the pH of water and soil and often kills organisms Can cause nutrients to leach from the soil Concentration of Toxins Either directly or indirectly by people Biological Magnification toxins become more concentrated as you move up trophic levels Best example is DDT. greatest effect on top predators Climatic Change Mainly referring to increase of CO2 due to burning fossil fuels and clear-cutting forests Greenhouse effect CO2 helps keep Earth warm by absorbing heat, preventing some of it from reradiating back to space. An increase in CO2 leads to an increase in Earths temp. thus leading to global warming Increase in temp causes the ice caps to melt which will have a global impact Ozone Layer The ozone layer is located in the stratosphere and helps prevent UV radiation from reaching the surface. It does this by absorbing UV radiation. UV radiation is a form of electromagnetic radiation that involves wavelengths of 200 400 nm (IB 54.24) The process of ozone absorbing UV radiation is important because UV radiation can damage tissues in living organisms. (IB 54.25) Ways that UV radiation damages living tissues (IB 54.25) Can cause mutations in DNA, thus increasing the risk of cancer (mostly skin cancer) May damage the DNA repair system, thus preventing DNA repair Can form free radicals which will attack and degrade living tissue; an example would be suppressing the immune system Can cause cataracts and sunburns if protection is not worn. Ways that UV radiation effects biological productivity. (IB 54.25) Increases mortality of phytoplankton in oceans Reduces the yield / photosynthetic rates among terrestrial crop plants Destroys nitrogen-fixing bacteria in the soil Having an adverse effect on the mentioned aspects will lead to adverse effects on food chains (remember that producers support the rest of the food chain; if production decreases, then biomass of other trophic levels also decreases.) 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" # $ % & ' ( ) * + , - . / 0 1 2 3 4 5 6 7 8 9 : ; < = > ? @ A B C D E F G H I J K L M N O P Q R S T U V W X Y Z [ \ ] ^ _ ` a b c d e f g h i j k l m n o p q r s t u v w x y z { | Oh+'0   @ L X dpx Chapter 54 Aiken UserNormalSamuel Salley2Microsoft Office Word@F#@^@>6@>6"՜.+,0 hp   Aiken County School DistrictH(  Chapter 54 Title  !"#$%&'()*+,-./013456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijlmnopqrtuvwxyz}Root Entry Fv1Table2CqWordDocument*bSummaryInformation(kDocumentSummaryInformation8sCompObjr  F Microsoft Word 97-2003 Document MSWordDocWord.Document.89q