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BIOL 230 Midterm Notes.docx

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BIOL 230
Roy Turkington

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BIOL 230 Midterm Notes: Ecology: (1) the study of growth, development, and interactions between species and their environment on a variety of scales (2) the experimental analysis of distribution and abundance (3) ways in which environmental factors and organisms interact to bring about patterns (4) study of everything present in a habitat and why they are present Ecological investigations: Descriptive ecology: surveying and collecting Functional ecology: asking proximate (immediate, now, near future) questions about how current factors act to influence organisms and systems Evolutionary ecology: asking ultimate questions about why organisms and systems today act as they do Accuracy: true representation of what’s happening in nature, all variables acting and unmanipulated Precision: all variables measured precisely, to determine their effects in the absence of “background noise” More manipulation  more precise  less accurate  lab-based Less manipulation  less precise  more accurate  field studies Natural experiments: completely unplanned events where data and observations could be collected Semi-natural experiments: planned, but not as an experiment Controlled manipulative experiments: planned experiments where variables are manipulated and controlled either on a large or small scale Replication: producing the same experiment in multiples in different but similar locations (i.e. multiple plots on a field)  not repetition (repeating experiment multiple times in same place or other places, but not because of ecological considerations)  Environmental heterogeneity  experimental site probably heterogeneous  takes into account either really good or really bad sites  Stochastic events  could happen + ruin or give weird results Global patterns of species richness:  Highest near the tropics, lowest near the poles  opposite for things like seabirds  Intermediate or variable in temperate regions  Must reflect difference between species added (speciation) and species loss (extinction) o As S increases, speciation levels off whereas extinction rises exponentially Area Hypothesis:  Physical  abiotic mechanism  Process of plate tectonics  arrangements of continents + oceans are changing  last 100 million years or so, large continental land masses near the tropics  Larger A more room for more species  hold more species  tropics have more species  Implies pop’ns able to exist at high abundance + on avg each pop’n will occupy large A  less likely to go extinct as result of stochastic events  Works well only for recent past  global patterns of S may have been diff. in past  More coincidental than mechanism Productivity Hypothesis:  Ecological mechanism  more productivity  higher “carrying capacity”  Tropics are constantly sunny, wet and warm  good producing conditions  lots for consumers to eat  lots of consumers to eat  encourages low extinction rates + high speciation  I.e.) good conditions for growth + survival  plants are productive  herbivores are productive o Predators become numerous + diverse  keep prey abundances low  less likely to be driven extinct by competition o Steady food supply  little niche overlap  even unspecialized predators can persist  No starvation, little competition  low extinction rates + specialization  speciation = high S  Claims “carrying capacity” is greater: o More productive, large pop’ns o Lots of low-abundance pop’ns o Carrying capacity is pop’n specific, not based on community Museum Hypothesis:  Evolutionary mechanism  less disturbances, lower extinction rate, more speciation time  Disturbances strike more often + more severely at higher latitudes  more extinctions/unit time  Tropics have been compressed by large scale disturbances  maintained tropical conditions  relatively fewer extinction  long-term persistence  Long history of consistent, relatively undisturbed systems  more time for excess of speciation over extinction to occur  Cradle Hypothesis: tropical diversity acts as a “source” for higher latitudes  when conditions are favourable, dispersal occurs Species-Area Graphs:  Show the role of area, comparing islands to other patches  Steeper slope of line (after logged)  greater difference in species richness among sampling areas  Mainlands + islands controlled by rates of dispersal and extinction o Mainland  immigration rates greater, extinction rates lower  A has smaller effects on these factors  gentler slope Rescue Effect:  Species X lost at particular locality by stochastic events  resources capable of supporting Species X, unused  X individuals from neighbouring localities move in  short-range dispersal  Adaptive dispersal: individuals gain advantage by moving into new area  little to no competition  Smaller A  fewer X individuals  same size disturbance  kills all individuals  cannot operate Extinction vs. Immigration Rates on Islands:  Area influences mostly extinction rates  in a smaller area  smaller pop’ns  higher densities  takes a small disturbance to lower abundance below sustainable value  i.e. more likely to go extinct statistically  Distance influences mostly immigration rates  further away from mainland or source  harder to reach/ less likely to reach  lower immigration rates Equilibrium Theory of Biogeography:  As S increases, extinction rates increase exponentially and immigration rates decrease exponentially  Where they cross, there’s an equilibrium  the ideal species richness  At S : eq o Disturbance  initially E>I  SE  eqS  more competition  E increase until E=I  E Trends: o S low  life easy  few predators + competitors o As S increases  more probable that resources will be used up efficiently  i.e. little to no leftovers  species expect reduction in density  more likely to fall below sustainable size o S high  pop’ns are small + stressed  disturbance or resource shortage  easy extinction o Affected by A  smaller, lower S; larger, higher S  I Trends: o S small  any successfully establishing species will be new  relatively high o Source has limited number of species available to reach island  these species will arrive + establish quickly  no longer count as new  rate reduces o New species run out  all have already reached the island  trails off the zero o Affected by d  farther, smaller S; closer, bigger S 6 Biogeographic Regions: 1. Nearctic  North America 2. Neotropical  South America + Caribbean 3. Ethiopian  Africa (minus northern tip) 4. Oriental  South Asian  India, Thailand, Malaysia, etc. 5. Palearctic  Eurasia 6. Australasian  Australia + New Guinea  Vicariance: the evolutionary separation of a species due to barriers  a range of distribution in the past becoming a patchy distribution in the present o Major cause of distinctness of regional biotas  Endemism: limitations of species or sets of species to one area  Vicariant biotas come into contact  dispersal of previously isolated organisms  Glacial periods  colder periods  less forest  more grassland  easier corridors for dispersal o Lower sea levels  more land exposed  land bridges for dispersal + more room for settlement Filters: factors limiting the distribution of organisms, determine which species will be able to become predominant in an area 1) Regional Species Gene Pool  gamma diversity  all species within reach for potential dispersal F1) Dispersal  weeds out species unable to reach a specific habitat  lack capacity to move there  distance, time, terrain F2) Abiotic factors  weeds out species unable to withstand habitat conditions  T, pH, moisture F3) Biotic factors  species interactions  weeds out species which cannot tolerate the presence of other organisms already established  predators, competitors, etc. 2) Local community  alpha diversity  all species within a locality Alpha diversity: count of all species present in one site within the study region Gamma diversity: count of all species present in all sampling sites in the region defined by you Beta diversity: measure of relative similarity of alpha regions in the gamma region (species turnover)  measures species-sharing within localities  high when many species are narrowly localized  relates well to filters  sites have different filters, i.e. differ in distances from other areas with other species present, in what types of abiotic +biotic variables prevail  similar filters  low Beta Resource: anything which is in limited supply, which will be unavailable to others after use, which is required for survival, which cannot be replaced by an alternative  essential, depletable, nonsubstitutable Conditions: property
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