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BIOL 215 Notes for Final.doc

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Biology (Sci)
BIOL 215
Catherine Potvin

October 13 2009Lecture 13Ecological NicheEcologythe relationships between organisms and their environments including biological as well as physical and chemical properties of environmentAims of ecology are to describe and understand the distribution abundance and production of organisms in their environment With the ultimate goal of being able to predict changes in environment and organisms when something may occur and why Observation five species of warblers coexisted in the same habitat Through careful observation it was noticed that the warblers lived in same tree but did not spend time in the same part of the tree at the same time They were living in different nichesThe Niche the environmental factors that influence the growth survival and reproduction of a species All factors necessary for its existencewhen where and how a species makes its livingFactors influencing where organisms live in their environment includeResources N P Ca etc foodPresenceabsencequantity of light photoautotroph are influenced by light availabilityOther species and predatorsWaterTemperatureTemperature affects the metabolic activities of all organisms because the biochemistry of cells is catalyzed by enzyme and their activity is influenced by ambient temperature Enzyme reaction rates are proportional to temperature have higher catalysis rates at higher temperature At very high temperature enzymes will degrade and catalysis rate falls off Acclimation to temperaturephysiological changes in response to temperature changes For example atriplex lentriformis a desert shrub grown at two temperatures 4330 and 2318 DayNight Temperature dependence of microbial growth on the organism level Environmental heterogeneityMicroclimate is the climate experiences at scales of kilometers or meters or centimeters shade of a tree on a sunny day Influenced by many factors including altitude T declines as high increases Vegetation Soil colouroWhite sand beach reflects all wavelengths of visible lightoBlack sand absorbs all wavelengths of lightAspect north facing vs south face slopeAquatic vs terrestrial environment aquatic environments show less temperature variation than terrestrial environmentsHabitatthe physical place where organisms live eg Tropical rainforest bottom of a lake hot springNicheexist within habitats Includes physical factors such as temperature and moisture biological factors such as resources and predators The intensity of competition between species suggest the degree to which their niches overlapLaw of minimums states that each species has a minimum requirement for every factor necessary for its survival and growth Eg Minimum T or lightLaw of tolerance states that even factors necessary for survival and growth can be stressful when present in too great an amount1 The availability of niches within a habitat varies in times and spacewhich influences the abundance and distribution of the speciesFeeding niches of finches show a relationship between body size and seed size The kinds of seeds eaten by the bird correspond to beak size During the drought of 77 larger birds capable of cracking hard seeds survived at a higher rate Consequently the population was dominated by larger birds at the end of the drought 2 New species invasive species or as a result of speciation can spread rapidly within a habitat as they occupy their niche Eg Zebra mussel bivalve in North America spartina anglica is a hybrid species that arose around 1960s unlike its parents its able to tolerate saline habitats and waterlogged soils Hybrid species spread rapidly throughout coastal Europe Australia and China where it was planted to stabilize mudflats Fundamental niche the physical conditions under which a species might live in absence of interactions with other species generally only considers abiotic factors temperature moistureRealized Niche is the part of the fundamental niche that an organism actually occupies Limited by biotic interactions such as competition predation disease and parasitismExample chthamalus and balanus are barnalces that grow in the intertidal regions on rocky shores They produce larvae which settle on the rocks The larvae grow into adults Realized niche of chthamalus was much smaller than that of balanus because balanus is able to displace the fundamental niche of chtamalus Measurement of niche breadth Competitive exclusion principle two species with identical niches cannot coexist indefinitely October 20 2009Lecture 14Population Distribution Abundance and GrowthRequired reading Molles p 302321p 266268Ecosystem the grouping of all populations of all species and the physical environment they inhabit Population a group of organisms of a single species inhabiting a specific areaThree main characteristics1Distributionthe size shape and location of the area occupied by a population2Densityindividuals per unit surface area3Abundance Largescale patterns of distributionLimits of population distribution1Species have different methods of dispersal across landscape2Factors allowing growth and establishment in species upon reaching a new locationClimate temperature and moistureNutrientsPhysical factors wave action desiccationEx Tiger Beetle Cincindela longilabrisThe tiger beetle lives at higher latitudes and elevations than most other species It is a widespread species with many populations that span over a large geographic range but always found in mountains cold climate A factor that promotes growth and establishment of the beetle in cold climates is an evolved physiological trait a high metabolic rate This demonstrates how physical environment limits species distributionEx Kangaroo distributions and climate Relationship between climate moisture and distribution is demonstrated by the distribution of three kangaroo species in Australia The Eastern Gray Kangaroo inhabits the eastern 13 of the continent wet climate The Western Grey inhabits the southern and western regions wet and dry The Red Kangaroo inhabits the interior arid and semi arid Limited distributions may not be determined by climate directly Climate often influences species
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