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Biology (Sci)
BIOL 215
Catherine Potvin

Lecture 13OCT 14Ecology the study of relationships between organisms and their environments which includes biotic and abiotic componentsThe aims of Ecology are to describe and to understand the distribution abundance and production of organisms in their environmentUltimate goal is prediction MacArthur found 5 different species which occupied the same treesHow were they able to coexistThey occupy the same tree but different partsThey are occupying the same habitat but different niches which limits their interactionsPrevents them from competing and allows them to coexist Factors that influence where organisms liveResources food Light photoautotrophsOther species predatorsWaterTemperature will be focused on TemperatureTemperature affects the metabolic activities of all organismsAll biochemical reactions are catalyzed by enzymesEnzyme reaction rates are proportional to temperature Enzyme Levelacetylcholinesterase is important in neurotransmissionTrout have 2 forms of the enzyme One which works well in cold temperaturesand one that works well in warmThese two forms match the temperature regime that the fish encounters in winter and summer These trout are then restricted to environments where the enzymes are most active Physiological LevelPhysiological differences reflect environmental differences and evolutionary historyMost species perform best in a narrow range of temperature Acclimation to TemperaturePhysiological changes in response to temperature changes Organism LevelTemperature is directly related to population growthHowever if the temperature gets too high it can kill or injure an organism Laws of Minimums and ToleranceLaw of Minumums states that each species has a minimum requirement for every factor necessary to its survival and growthLaw of Tolerance states that even factors necessary for survival and growth can be stressful when present in too great amount How does temperature vary in the environmentMacroclimate is the climate experienced at large spacial and temporal scales latitudinal zonesMicroclimate is the climat experienced at scaled of kilometers or meters or centimetersIs influenced by factors like altitude vegetation soil colour aspect south facing slopes will have grass while the north ones will have trees Habitat Temperature VariationTemperature vaires widely among and within environments Habitat vs NicheA habitat is the physical place where organisms live eg tropical rainforest bottom of lakeMany organisms occupy the same major habitat Organisms that live in similar habitats do not live in the same place in the habitatthey occupy unique nichesPhytoplankton live in the same habitat lake but they occupy different niches within the habitat depth NicheAppropriate combination of conditions for a species to thrivePhysical and biological factors are determine nicheThe ecological niche of an organism is the position it fills in its environment comprising the conditions under which it is found the resources it utilizes and the time it occurs thereSo we can look at the specific requirements of each species beginning with one part of its ecological nicheBy combining different relevant factors and related data of the presence of a species it is possible to construct 3D cubes in space to predict where organisms liveThis is referred to as the dimensional hypervolume the nicheThe set of paramaters is infinite so the parameters must be chosen Every set is uniqueThe availability of niche at a certain habitat varies in time and spacewhich influences the abundance and distribution of the speciesOverlap of niche results in conflict Feeding the Niches of FinchesOn the a Galapagos island there are three main finchesThey all have different sized beaks to suit the seeds they eatThe feeding niche can be determine by the beak sizeThere is a variability of beak size within each speciesThere was a drought that killed 85 of G fortis but it didnt affect all of them that badly because they occupied different niches It favored the larger G fortis Spartina anglicaHybrid speciesUnlike parents it is very tolerant of saline habitats and waterlogged soilsSpread rapidly throughout coastal Europe Australia ChinaDistribution predicted by a few physical variablestide levels fetch Fundamental niche is a niche with appropriate conditions that a species might live inRealized niche is part of the fundamental niche where a species actually live Lecture 14OCT 19Population DynamicsBasic demographySurvivorshipReproduction 1 Basic DemographyA population is a group of organisms of a single species inhabiting a specific areaPopulation dynamics studies the behavior of populations such as increases and decreases in population size Want to predict the growth or reductionThe two most important aspects of demography are death and birthThe simplest case NPNbNt1attNis the number at the end of a seasont P is the probability of survival to the next seasonab is the average number of offspring produced per adultTwo factors important in determining population growth1 Sex ratioThere is a bottleneck when there are too little females Males can reproducde with many females can only bear a limited number of offspring2 Age structureDemography is always female based very hard to track paternitySemelparousOrganisms which reproduce once in a lifetimeUsually have a lot of offspringEasy to monitorCorypha the tailipot palm
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