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IB Biology Chapter 4 Ecology Species ,communities, and ecosystems • Interdependence of Living Organisms • 1980-eruption @ Mt St. Helen’s-see p.172 What is a species? • Defined as a _____________________ • Made up of organisms that• Have similar physiological and morphological (ie. Size and shape of an organism and/or its parts) characteristics that can be observed or measured • Have the ability to interbreed and produce fertile offspring • Are genetically distinct from other organisms • Have a common phylogeny(ie.family tree) That can interbreed and produce fertile offspring • Challenges to this definition: • Sometimes members of separate but similar species mate and succeed in hybrid offspring-eg.horse+zebra-produces--zebroids-both parents belong to Equidae family-related but not same species-do not have same # c’somes-why offspring usually infertile • Some populations may be able to interbreed,but do not do so because they are in different niches or separated by long distances • How do we classify organisms that reproduce asexually • What about infertile offspring-Do we exclude humans unable to reproduce from species? • What about in vitro fertilization • Domesticated dogs-while different breeds-are same species and can interbreed Hybrids • To understand fertile offspring-♀(female) horse + ♂(male) produce_____-mules cannot mate to make more mules-mule is ∴ called_____________________________________ • ♂lion and ♀ tiger produce liger hybrid • Challenges hybrids face cont as a population inc.infertilty, • Other hybrids: • ♀ horse + ♂ donkey=mule • ♀ horse + ♂ zebra=zorse • ♀ tiger + ♂ lion=liger mule Interspecific hybrid Populations can become isolated • Grp from a species separated from rest of species may evolve differently when compared w/rest of populationeg.mice have inadvertently crossed oceans on board ships-as they searched for food-may even end up islands away-mice produced on new islands are reproductively isolated-may end up w/ a different frequency of certain alleles-eg fur color • Other things can produce isolation-such as mt. ranges-tree snails in Hawaii-present on only one side of volcano • Also temporal isolation-early migrating birds may have genes isolated from later arrivals • Behavioral isolation-such as different mating calls from same species of birds • Over time-some of these may result in speciation_________________________________(refer to ch 10.3) New species formed from old Autotrophs and heterotrophs • Autotrophs-capable of ________ -synthesize organics from simple inorganicsusually by photosynthesis • Because the food they make is eaten by others • __________ • Examples-cyanobacteria,algae,grass,trees photosynthesis producers • Heterotrophs—cannot make own food from inorganics-but must get from other organisms-from autotrophy and heterotrophy-called ____________________because rely on others, ingest organic matter • -Examples-zooplankton, fish, sheep, insects consumers E. Consumers • Heterotrophs-whether we from autotrophs or products of other heterotrophs • Take in energy-rich C-compounds, such as sugars,proteins,and lipids • Only part of human’s diet that we synthesize is Vitamin D cholesterol molecule in our skin is modified by light into Vitamin D • Detritivores • Eat non-living organic matter-dead leaves, feces, carcasses-eg. Earthworms,woodlice Saprotrophs • Live on or in non-living organic matter, secreting enzymes and absorbing the products of digestion • Fungi, some bacteria-decomposers Communities • Group of populations living and interacting with each other in an area • 1 species may interact by feeding on another or being eaten • May provide vital nutrients for another(e.g.-Nfixing bacteria) • One species may provide protection for anothere.g.-aphids protected by ants • One may rely on another for its habitat-e.g.parasites Ecosystems abiotic • ______________-non-living components of environment(air,water,rocks)-such measurements include _______________-often using electronic probes and data-logging techniques • These things have a large influence on living things • ________________-living factors • Random sampling using quadrats(to determine the frequency and distribution of a species)-see page 178 • Systematic sampling-using a transect= a line traced from one environment to another-may be a 1,25-50 m long-may set up quadrat every meter along transect or at specific intervals along transect-counting the organisms that hit each quadrat and then counting organisms found in each quadrat-no random numbers….see p. 179 Temp,pH,light levels,and relative humidity biotic Where do autotrophs get their nutrients? • From inorganic surroundings • Photosynthetic organismsphytoplankton,cyanobacteria,and plants--photosynthesis • Producers and start of food chain Nutrient Cycling • • • • • • • • • Find need nutrients w/in own habitat-C,N,etc Decomposers Accessing nutrients through decay Saprophytes and detritivores break down body parts of dead organisms Digestive enzymes convert organic matter into more usable forms for themselves and other organisms-e.g. proteins from dead organisms are broken down into ammonia(NH3) and then, in turn ammonia has its N converted into nitrates(NO3-) by bacteria. This recycles nutrients so they are available to other organisms-instead of locked into carcasses or waste products Decomposers help w/formation of soil ________-rich black layer composed of organic debris and nutrients released by decomposers Decomposers form humus in compost piles compost The sustainability of ecosystems • Through recycling of nutrients, ecosystems can contribute to be productive and successful for long periods of time • Convert CO2 to C6H12O6-by producers-used then to make complex carbs-like cellulose –or lipids and proteins • Consumers eat producers, and digest the complex organic compounds into simple building blocks---amino acids and sugars,eg,for growth and energy • When the consumers die,their cells and tissues are broken down by decomposers-minerals ret’d to soil---for producers ,once again-completing cycle • N-cycle-N important for nucleotides and amino acids— essential to DNA and proteins-essential to existence • Cycle starts w/ N in gas form in atmosphere(N2)—Plants and animals can’t use N2—some bacteria transform it by N-fixing Then absorbed by plant roots(some plants have N-fixing nodules attached to roots)----Plants and animals return N to soil in variety of ways—e.g. ,ret’d by decomposition,byurine,feces Energy Flow • Importance of sunlight to ecosystems • Best studied ecosystems on earth’s surface, relying on sunlight-are the focus here • All life relies directly or indirectly on sun B. Role of photosynthesis • Take CO2 and convert to C6H12O6 • Light energy converts into chemical energy(food)-rich in energy due to chemical bonds between C and other atoms • Chemical energy measured in calories or kilocalories(kilocalories on pkg’ing) • Release energy by digesting,also to burn Food chain Process of passing energy from one organism to another • Food chain defined as _______-arrow shows direction of energy flow • Trophic level=indicates how many organisms the energy has flowed through • 1st trophic level has autotrophs or prodcers;next level primary consumers; next secondary consumers Sequence showing feeding relationships band energy flow between species Cellular respiration and heat • As grasshoppers consume grass, chemical energy is used for cellular respiration/glucose converted to CO2 and H2O • This takes a sm amount of heat in each of grasshoppers cells…heat lost to environment/thee nutrient and energy passed on to next consumers • Cells of decomposers also do cellular respiration and thus release heat to environment Heat cannot be recycled • Heat not actually lost due to law of conservation of energy, but cannot be used again as biological energy source Where does the heat go? • Heat lost from ecosystem, radiates into surrounding environment/ecosystem cannot take back heat to use it-not recycled like nutrients • Food chain only adversely affected by the lost heat if sun is lost-thus affecting food chains • Only chemical energy can be used by next trophic level and only a small amount of energy absorbed is converted into chemical energy • No organism can use 100% of energy in organic molecules-typically only 10-20% used from previous step…~ 90% lost Main reasons not all energy in n organism can be used by all other trophic levels: • Not all of an organism is swallowed as a food sourcesome parts rejected and decay • Not all food swallowed can be absorbed and used in body(e.g.-owl pellets) • __________________ • There is considerable heat loss from cellular respiration @ all trophic levels-most animals have to moverequiring more energy than plants-Warm blooded animals use much more Some organisms die w/o having been eaten by member of next trophic level see p.188 Pyramid of energy • Used to show how much and how fast energy flows from one trophic level to the next in a community • Units=energy per unit area per time=kilojoules per square meter per year(kjm-2yr-1)—take into account rate of energy produced as well qty Because energy is lost-each level smaller than previous—cannot have higher level wider than lower level Food webs and energy levels in trophic levels • # of organisms in a chain as well as qty sunlight energy available @ start decide length of chain • Biomass of a trophic level=estimate of mass of all organisms w/in that level-expressed in mass units, but also take into account area or volume eg.3tons acre• 1yr-1 • Amount of sunlight reaching fields affects biomass, therefore sunnier region produce more biomass wheat • Some molecules along the way cannot participate in biomass because they re lost-e.g. CO2 lost in cellular respiration, water during transpiration evapoartion from skin,urea lot in excretion• ∴not all energy passed to next trophic level and not all biomass passed on • Sometimes foodweb rather than chain is used because there may be many feeding relationships going on III. Carbon cycling • Crucial element to life • Life on earth is referred to as C-based • In biosphere as carbs, lipids, nucleic acids and proteins • Also in atmosphere as CO2 and lithosphere ____________________________ i.e.-places where rocks are found . • Petroleum-from which gasoline, kerosene, and plastics are made-rich in C having come from decomposed organisms of millions of years ago • Constantly cycled between living organisms and inorganic processes making C available-e.g. C atoms composing the flesh of a giraffe come from the vegetation it ate • When cellular respiration is complete-CO2 released into atmosphere • When organisms die, scavengers eat decomposers break down—which release CO2 back into atmosphere from cellular respiration • Glucose also starting point for other organicse.g. lipids and amino acids-which go into cell membranes and proteins-enzymes • Other elements added to glucose-such as N C in aquatic ecosystems • CO2 water soluble • Absorbed by bodies of water • Organisms living in water also produce CO2 (by cellular respiration) • ____________________________ As CO2 is dissolve in water it forms an aciddecreasing water’s pH The H+ influences pH The HCO3 – important inorganic C-based molecule that participates in C-cycle Cycling of CO2 Absorbed by photosynthetic autotrophs such as bacteria, phytoplankton, plants, and trees. They are eaten by consumers, using C in their bodies Cellular respiration (hereby abbreviated as cr) from all trophic levels produce CO2-releasing it back into environment Diffuses into atmosphere or into water Methane in C-cycle • Members of Archaea include methanogensanaerobic • ___________________________ • Methanogens also common in wetlands, where they produce marsh gas (may glow) • Also produce CH4 in digestive tract of mammals-inc. humans-hence the concern w/cattle herds-contribute to greenhouse effect (next section) When they metabolize food, they produce CH4 (g)-a waste gas The oxidation of methane • CH4 main ingredient in fossil fuel__________________ • The C found in CH4 borrowed from CO2 molecule removed from atmosphere MYAduring photosynthesis, it then took CH4(g) millions of years to form and accumulate underground • When we burn natural gas, we return C to atmosphere as CO2 • What would normally take millions of years to be cycled is thus released rapidly released Natural gas Peat as a fossil fuel • ____________=partially decomposed plant matter • Waterlogged, found in certain wetlands-e.g. Mires and bogs in British Isles, Scandanavia, N. Russia, some of E. Europe, N. Canada, N. China, Amazon River basin, Argentina, N. USA9esp.Alaska), ans some of S.E Asia • Dark in color and only certain types of vegetation can grow on its surface-such as Sphagnum moss • Heterogeneous but at least 30% of its dry mass must be composed of dead organic material peat • Soil that forms peat is called a _______________typically 10-40 cm thick • Spongy---The high levels of water on peatland force out the air that would normally be between the particles of soil-creates anaerobic conditions—This allows microorganisms to grow but prevents growth of microorganisms that would help in plant matter decomposition • ∴ the energy rich molecules that would have been fed upon by decomposers are left behind and transformed, over thousands of years, into energy –rich peat. histosol • pH of waterlogged histosol-very acidic • not conducive to decomposers • this contributes to the accumulation of nondecomposed material • within the pools of acidic water- in these wetlands are unique organisms such as some aquatic beetles • to be usable as fuel, cut peat is dried out to reduce humidity. It is then cut into slabs, granules, or blocks and moved where needed • takes a long time to form and considered nonrenewable energy • when oil prices are high, peat can be a competitive energy source • many wetlands have been drained to replace w/forests and farmland • concern about wetland preservation has hindered some harvesting of peat…but also because of concern about unique species • also preserve because trapped pollen can reveal info about past climate Oil and gas as fossil fuels • When left in the correct conditions, partially decomposed peat can be further transformed into coal • Over millions of years, sediments can accumulate above the peat and weight and pressure of those sediments compress it • Under ideal conditions, sedimentation cont. until C-rich deposits are both under huge pressure and exposed to high temperatures (since they have been pushed below Earth’s surface) • Pressure and heat cause chemical transformations associated w/lithification____________________ • During lithification, the molecules are compacted and rearranged • The hydrocarbons-long chains-are of particular interest to industry due to the large amount of energy they hold-ready to be released by burning • Coal must be extracted from below ground to be used for energy-mining • Found in seams, where layers of sediments were deposited, covered, and then transformed and other twisted/deformed by geological forces over millions of years Which is the transformation of sediments into solid rock The C-H bonds hold a significant amount of energy, and because there is many-much energy to be released by burning In addition to coal, the chemical transformations underground can produce other petro products such as crude oil and natural gas • During the __________________________period MYA, some places in the world that are now dry were underwater-hosted much aquatic or marine life-inc. algae and zooplankton • The dry deserts of Saudi Arabia used to be under the Tethys ocean-in the time of Pangea • At that time, under ideal conditions for petro formation, dead remains of organisms in the water did not fully decompose @ the bottom of the oceaninstead forming layers of sediment w/silt Carboniferous • In ________-no O2 conditions-the decaying material started to form sludge, as parts of organisms cells decayed and others didn’t• The lipid component of cells not easily broken down-the accumulated lipid trapped in sediments from a waxy substance called kerogen • Kerogen is also rich in hydrocarbons and also is transformed by pressure and heat as sediments accumulate above it and cause it to rearrange • Natural production of kerogen-long process • Over millions of years and after geological transformation, kerogen in porous sedimentary rock becomes crude oil or natural gas (in g state)-both being less dense than rock, rising through the cracks to the surface Anoxic conditions • In order to be used by humans, petroleum products must be trapped and pooled under non-porous rock, preferably one bent by tectonic movement into a dome-as seen above-this allows large qty’s of useful gas and oil to collect together in a productive reservoir • Geologists study which parts of the world might contain exploitable gas and oil reserves • CO2 is produced when fossil fuels are used • Substances rich in hydrocarbons can be oxidized using O2 gas from atmosphere when they are burned • Wood, animal dung, can be used-inc. for cooking • Fresh, wet dung can be mixed w/other refuse from a farm and put into lg container, where methane producing microorganisms will decompose and ferment it to produce CH4(g)• Biofuels made in biogas generator take millions of years to form • In efforts to reduce fossil fuel consumption, some countries-e.g. USA and Brazil-have introduced biofuel programs using ethanol made from crops like corn and soybeans • The plant material is fed to microorganisms that ferment it and release ethanol-which is added to gasoline for carsreduces gasoline use • Standard vehicles cannot use more than 25% ethanol (need 75% or more gasoline)-gasohol • Esp. adapted vehicles can run solely on ethanol • w/a different technique, biodiesel can be made from vegetable oil or animal fat-such as from deep-fat fryers Limestone • marine organisms remove CO2 from water and some is used to make carbonate shells • C can be in form of CO@ dissolved in water or HCO3- ions • Coral polyps build coral reefs-they absorb 2 ions from seawater to build the reef-HCO3and Ca 2+---forming CaCO3(calcium carbonate)-basis for coral reef-sturdy • Other organisms also use CaCO3 to build shells about their bodies-mollusks-snails, clams, oysters, and mussels—when they die their shells accumulate at bottom of ocean • Microscopic foraminifera are usually on ocean floor and build shells---their shells accumulating in sediment after millions of years through lithification—forming limestone • A bldg. material • Carbon sequestration-taking C out of environment and locking-up in a substance for an extended period of time—if natural its bio- sequestration-helps maintain balance in c – cycle • Through biosequestration-accumulation of foraminifera shells as sediment at bottom of ocean can trap C in limestone for millions of years • Making of cement by people sues limestone-releases C back to atmosphere as CO2