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190 Cards in this Set
- Front
- Back
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what are the models and patterns of distribution? Examples of each? |
- clustered -- school of fish - uniform -- territorial animals - random -- distr of seeds of trees - linear -- migration - compound -- compound of multiple distrs |
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contrast cartographic vs ecological scale |
cartographic: smaller scale = wider view -- ratio between size of physiographic feature and representation ecological: spatiotemporal dimensions of object defined by grain and extent |
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what is ecological scale defined by? |
Grain: finest level of spatial resolution possible with given data set -- smallest measurement extent: size of study area or duration of time under consideration |
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what is extent in ecological scale? |
size of study area or duration of time under consideration |
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what is grain in ecological scale? |
finest level of spatial resolution possible with the given data set -- smallest measurement |
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how is scale defined by Dungan et al.? |
- observation - ecological phenomenon - analysis
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what is a natural vs unnatural spatial unit |
natural: right size in relation to what is being measured unnatural: not a perfect size |
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what is observational scale in Dungan et al.? |
- traditional definition of scale - size, shape, spacing and extent of sampling units - area of consideration - natural or unnatural spatial units |
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what is ecological phenomenon scale in Dungan et al.? |
the spatial or temporal scale of the occurrence or activity of an ecological entity or process |
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what is analysis scale in Dungan et al? |
- stat approaches used to summarise spatial data can alter grain and extent of data - specific to certain spatial stats (kriging, quadrat variance) |
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what do you consider when you have scaling issues? |
- description of eco phenomenon can change on the scale of observation and resulting analysis - our understanding of eco processes is dependent on the appropriate choice of scale - scale might be a continuous process without discrete holons/breaks - strive to identify variability between processes recognising domains of scale |
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what are domains of scale? |
sharp transitions from dominance by one set of factors to dominance by other sets |
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what are the limiting factors proposed by Rettie and Messier? |
how an animal decided between fine and course scale resources and fitness constraints -- choose smaller abundance of plants with less chance of predation over larger abundance of plants with higher predation |
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how do you perform a scale sensitivity analysis? |
incrementally assess larger scales of measurement and then test all the data for a scale effect |
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what is blocked quadrat variance and how do you perform one? |
measure changes in spatial structure as a functionof differences among quadrats/blocks |
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what does fractal d measure? What does it mean for its value? |
tortuousity of movement path if d = 1, linear line, 1 dimension of movement if d=2, 2 dimension movement -- brownian movement |
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what are Kreb's rules for eco data collection? |
- not everything that can be measured should - find a problem and ask a question that is relevant and testable - collect data that will answer your question and make a statistician happy - some eco questions are impossible to answer at the present - never report an ecological estimate without some measure of its possible error/precision - never confuse stat significance with bio significance - garbage in garbage out |
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what is a census? |
complete count of all individuals in a pop |
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what are the steps for a sampling design? |
- specify the stat pop and understand the relation to the bio pop - define the sampling (Experimental) unit - select a sample |
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how do you collect a simple random sample? |
- have a stat pop consisting of N sampling units - sample n units from N - number each sample unit, and use RNG to select sample |
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what are the simple random sampling methods not based on probability sampling? Issues with it? |
- accessibility sampling: restricted to units that are readily available - haphazard sampling: opportunistic sampling - judgemental sampling: investigator selects typical units -- judge before sampling - volunteer sampling: individuals volunteer to submit information/serve as subjects |
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What defines a stratified random sample? |
- stat pop of N sampling units divided into subpops - subpops do not overlap but = entire pop - sample each stratum separately, sample size n1, n2, n3, etc. - descriptive statistics are calculated for each stratum and weighted by proportion of entire stat pop |
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Why would you stratify a sample? |
- control for environmental gradients - sampling effort and technique may differ across areas - may reduce variation in sample across study area, increasing precision - collaborative field logistics may require stratification for each partner - can choose proportional or optimal allocation |
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what is a systematic sample? |
a sampling method used to sample evenly |
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what are the measures of pop density? |
- absolute abundance: number of organisms (or per unit area/volume) - population indices: indirect measure of pop change |
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Pros and cons of absolute abundance |
Pros: - absolute abundance allows standardized comparison among pops and over time - can relate to conservation and management actions cons: - expensive and difficult - interpretation can be hampered by poor precision or bias |
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pros and cons of pop indices |
Pros: - precise, affordable, common cons: - provides relative not direct measure of pop change - risk of bias related to methods - often represent a specific demographic of the pop - need to worry about a numerator and denominator |
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what is an open population vs closed population? |
open: allows for emigration/immigration closed: no emigration/immigration |
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when do you use the bias corrected mark recapture formula? |
when R<7 or M+C<N |
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what are the assumptions of the petersen method? |
- no change in ratio between marked and unmarked individuals during the interval between samples - all animals have same chance of getting caught in first and second sample - marking individuals does not affect their catchability or survival - animals do not loose marks between the two sampling periods and all marks are reported on discovery in the second sample |
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what are the fundamental parameters for mark recapture data? |
- phi: apparent survival from capture session 1 to session 2 - p: encounter prob of recapture at each interval |
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what are quadrat counts and their requirements? |
- counts of plants and animals across known areas -- simplest technique for density estimates - can be used with many sample designs
requirements: - area/volume of sample unit is known - organisms are relatively immobile during counting |
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what are line/belt transects used for? |
calculate density of animals in rectangular area |
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what is hayne's estimator? |
line/belt transect density estimator for birds being flushed |
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what is hayne's estimator? |
line/belt transect density estimator for birds being flushed |
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what are the assumptions of line/belt transects? |
- animals directly on transect line will never be missed - animals do not move before being counted and no double counts - distance are measured exactly with no measurement error - sightings of individual animals are independent events |
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what are the plant distance methods for density estimation and what are the issues with them? how can you correct them? |
- point to organism: underestimates density - organism to nearest neighbor: overestimates density - use diggle's estimator |
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how are models linked through abstraction and interpretation? |
abstraction: include only most important components of real system to simplify and make easier to understand interpretation: model components (parameters, variables) and behaviour that relate the model to real systems/processes |
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what is the trade off of abstraction for interpretation |
abstraction makes the system simpler and easier to understand, but decreases interpretation/realism interpretation makes the system more realistic and closer to real-life, but makes it more complicated |
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what are the types of mathematical models in pop eco? What do they do, what are the problems/advantages? |
analytical: - model continuous change in pop numbers with time, exact solution of instantaneous change over continuous time - issues: not all pops change continuously with time, difficult to solve for pop models with many variables Numerical: - pop change at discrete time steps (eg. day, year) that is defined by life history of organism - uses recursive (iterative) math advantages: mathematically simple, difference and differential equation might be approx equal |
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what is r in pop growth |
intrinsic rate of increase, instantaneous growth rate, per capita growth rate, malthusian parameter |
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how do you interpret r in growth rate? |
r>0; pop increasing r<0; pop decreasing |
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what is the discrete growth rate? |
r(d) -- constant % change in pop |
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what are the parameters of a simple numerical model? |
r(d) -- discrete growth factor lambda -- pop growth with discrete breeding cycles |
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What is lambda in pop growth? how do you interpret lambda? |
discrete growth rate, finite growth rate, multiplicative growth rate L>1; pop increasing 0<L<1; pop decreasing L cannot be negative |
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how do you convert lambda to different time intervals |
convert lambda to r (ln(L)=r) then divide or multiply to correct time scale, then convert back |
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what are the assumptions of the density independent model? |
- immigration & emigration balance - all individuals have equal prob of reproduction or death - asexual repro - sex ratio has no effect on growth - environmental resources are infinite |
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what are the assumptions of the density dependent growth model? |
- closed population - asexual - environmental resources are infinite - all individuals have equal chance of living or dying |
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what are density dependent factors? |
- factors that influence pop change at a rate that is a function of pop density -- effect increases with pop size |
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what is the Allee effect? |
positive density dependence due to limitations of pop processes at small numbers |
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what do r and lambda equal when the population reaches K? |
r=0, L=1 |
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what are signs of density dependence? |
- increase in mortality of immature animals - increase in age of first repro - reduction in repro rate of adult females - increase in mortality of adults - more immigrations vs emigration - occupancy of marginal/poor habitat |
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how do you diagnose density dependence in plants? |
- slow to fast growth in response to competition - unable to disperse in response to competition - seedling mortality increased - adult mortality constant relative to competition - poor seed establishment |
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where is the point of maximum growth in density dependence growth? |
at k/2 |
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what are the assumptions of the verhulst model? |
- constant K -- resource availability is not constant - linear density dependence -- each individual added causes incremental instantaneous decrease in per capita rate of pop growth - no sexes, emigration, immigration, age groups |
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what is population regulation? |
when a population's size is a function of density dependent responses to K -- density related negative feedback |
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what is population regulation? |
when a population's size is a function of density dependent responses to K -- density related negative feedback |
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what are the methods for detecting regulation? |
- perturbation experiment: reduce or increase number of animals/plants - relate variation in density of multiple populations to pop growth rates - relate individual pops to index of resource availability |
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what is compensatory mortality? |
mortality resulting from harvest to reduce the number of individuals -- no change in survival rate due to harvesting replacing natural death from regulation |
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what are the essentials for regulated compensatory mortality? |
- must know K and have a pop regulated by K - pop produces too many animals for K - surplus animals die from natural causes - harvest surplus animals - compensatory decrease in non-hunting mortality - no net additive increase in mortality at low to intermediate harvest |
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what are the essentials for additive mortality? |
- harvest more animals that would die from regulatory factors - harvest animals from population that is limited, not regulated |
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can compensatory mortality increase N? |
yes and no - increase seasonally -- harvest animals before bottleneck/food limitations - doomed surplus doesn't immediately die, consuming resources before death |
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what are the requirements so that population N does not exceed K? |
- organisms need to be aware of their resources - pop has capacity to control resource use - instant self regulation of birth/death |
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what is the difference between short-term and long-term K |
short term K regulates the pop over short periods of time (Eg. months) while long term K regulates the pop over long periods of time (eg. years) |
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when can the population exceed K |
when the short term K does not equal the long term K |
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what does a difference in short term and long term K lead to? |
pop cycling |
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what is population cycling? |
when populations increase and decrease with a regular period or chaotic pattern |
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can limited populations also cycle? |
yes, however it is a limited cycling dynamic -- respond to external limiting factors |
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what describes cycling? and what rules cycling? |
- ruled by growth rate and time lag (tau) - cycling is described by amplitude and period |
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what is amplitude and period in population cycling? |
period: peak to peak of cycling pattern amplitude: from peak of cycle to equilibrium position |
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what were the hypotheses for population cycling? |
- amplitude of pop fluctuations is positively corellated with latitude (higher lat = higher amplitude) - the more complex the ecosystem is, the less the population fluctuates - the more connected the landscape is, the more area for animals --> less fluctuation - amplitude of fluctuations is a function of plant productivity or predator limitations |
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how does r affect population cycling? |
if r is larger, amplitude of cycling is larger |
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what influences pop dynamics? |
- births, deaths, immigration/emigration - positive and negative density dependence - age |
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what is age structure in age dependent pop growth? |
define birth and death rates for age classes based on time spans significant to life history of spp |
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what is stage structure in age dependent pop growth? |
define birth and death rates for age groupings based on time spans of significance to life history of spp -- simplification of continuous demographic changes and age structure |
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how does age structure differ from stage structure in age dependent pop growth? |
age uses age classes that are equal in time whereas stage groups together those age classes into ones of significance |
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what is a life table and what does it allow you to calc? |
- table of age-specific survival, death, and fecundity rates for a pop - net repro rate/individual, instant growth rate, generation time |
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what are the different symbols used in life tables? |
- x: age class - S(x): cohort size (n indiv.); survivors at time x - b(x): fecundity; fem. offspring/fem./time - g(x): P of survival from x to x+1 - q(x): P of mort from x to x+1 - l(x): P of survival from birth to start of age x - l(x)*b(x): contribution age class (x) makes to pop growth R(0) = sum[l(x)*b(x)]: avg net repro rate/indiv. G: generation time |
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what does it mean when R(0) = 1.0 in a pop? |
stable pop (no growth/decline) |
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What is the main issue with life tables? |
only works with short-lived spp |
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what are the different methods for making life table data? Type? |
age at death recorded directly (Cohort LT): - mark single cohort and follow through time; each indiv check at each time step - create S(x) for table Age at death recorded for several cohorts - mark multiple cohorts and follow through multiple age classes, checking each indiv at each step - assume all indiv.s from same pop Age structure recorded directly (Current LT) - number of indiv of age x compared with number that die before x+1 resulting in g(x) and q(x) - multiply g(x) by hypothetical pop to calc S(x) and l(x) |
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what are the matrices for pop growth with age structure? |
age class matrix: Leslie matrix Stage class matrix: Lefkovich Matrix |
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assumptions and limitations of age structure model? |
- Exponential growth -- no K - flexibility to incorporate other vital rates (immigration/emigration) |
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What are vital rates? |
fundamental parameters of pop change: - Birth rates: # individuals born/individual - number of individ. die/indiv. |
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what are the types of birth rates? |
- fertility/birth rate/natality: actual # of offspring per adult female per unit time - fecundity: potential number of offspring produced per unit time - recruitment: # of young that survive into next age class |
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what are the direct methods to measure birth rates? |
- observation - collect reproductive tracts from managed populations (placental and ovarian scars through destructive sampling) |
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what is survival rate? |
proportion of animals alive on day "d" that are still alive on day "d+1" |
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what is survival probability? |
prob that an animal alive on day d will still be alive on day d+1 |
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what is longevity vs senescence? |
Longevity: max age a member of a pop can reach before death senescence: max age a member of a pop can reach before repro stops |
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what is finite survival? |
constant time interval: # of indiv alive at end of time period divided by # of indiv alive at start of time period |
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what is an r-selected spp vs k-selected spp? |
r-selected: - high repro + low offspring investment - continuous growth with high mort. K-selected: - stable environment, low repro - few offspring + high offspring investment |
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what is a survivorship/mortality curve? |
proportion of individuals surviving/dying vs age or time |
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what are the assumptions of daily survival estimator? |
- no immigration/emigration - handling does not affect survival - survival has constant prob - no individual lost from study - marking/tracking does not affect survival |
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what are the advantages the kaplan-meier method? what are the aliases? |
Aliases: - product limit estimator - staggered entry estimator Advantages: - marked individuals checked on non-regular schedules - new left-censored individuals added to sample so that large n retained - accounts for right censored data |
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what is right-censored data for left-censored data? |
right-censored: individuals lost from monitoring but not assumed dead left censored: individuals added to sample so large n retained |
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what are the assumptions of the Kaplan-Meier estimator? |
- random sampling relative to inherent survival - survival times independent for each animal - capture/tagging doesn't change survival - censoring is random - newly marked animals have same survival function |
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what is a deterministic outcome? |
- predetermined outcome - prediction of deterministic models always consistent given consistent input parameters |
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what is a stochastic process? |
- a process with an indeterminate or random element |
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how do you estimate a stochastic process? |
use probabilities to form a curve |
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what will extreme stochasticity lead to regardless of r or lambda? |
extirpation |
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what are the types of stochasticity? |
- environmental stochasticity - demographic stochasticity - genetic stochasticity - natural catastrophes |
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what is environmental stochasticity? |
temporal or spatial variation in extrinsic factors (eg. quality of habitat, interspecific interaction, incidence of disease or parasites) |
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what is demographic stochasticity? |
random fluctuations in intrinsic pop parameters (eg. birth and death rates, emigration, immigration, sex ratio, age structure |
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what is genetic stochasticity? |
- randomness in pop genetics leading to change in individuals' fitness |
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what is a pop viability analysis (PVA)? |
model used to measure the impacts of stochastic processes on pop/species persistence |
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what are the limitations of PVA? |
- poor data -- hard to obtain vital rates and associated variance - single pop -- lack of community interactions - linear pop growth -- density dependence and compensation poorly represented - difficult to assess results -- no standard protocol to identify a valid PVA |
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what is a community? |
- assemblage of spp that live in an environ and interact with one another forming a distinct living system with its own composition, structure, environ relations, development, and function - associations of plants and animals that are spatially delimited and that are dominated by one or more spp or by a physical characteristic |
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what are the defining criteria for a community? |
- collection of organisms (2 or more spp overlap and interact at a location, not necessarily same time) - focus on interactions and outcomes for dynamics across multiple populations - study patterns and processes |
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what is a pattern vs a process in community ecology? |
pattern: describe communities and their collections of spp, unique distribution process: interactions among spp that result in communities |
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what is ecosystem ecology? |
- interest in abiotic interactions |
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what is landscape ecology? |
almost any set of interactions at any scale but consider patches as a focal point study pattern, processes and scale |
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what is habitat ecology? |
- spatial interactions between organisms and patches of resources |
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what are the subsets of communities? |
- guild: collection of spp that use similar resources in similar ways - taxocene: set of taxonomically related spp within a community - trophic levels: subsets of spp within communities that acquire energy in similar ways - biomes/ecozones: basic categories of communities that differ in their physical environments and life styles of dominant organisms |
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how do you ID a community? |
- taxonomy: presence of one or more dominant spp - statistical: set of spp whose abundance is correlated over space and time - interaction: must interact to be part of a com; taxonomy and ecology do not guarantee membership |
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what are habitats? |
- location where organism lives - the conditions of the environment necessary to support an organism - resources and conditions present in an area that produce occupancy -- including repro and survival -- by a given organism |
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what is habitat use vs preference vs selection: |
use: occurrence or frequence of an organism in a habitat preference: choice of some resource when all resources offered in equal amounts selection: differential use of habitats relative to availability of those habitats |
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what are the evolutionary premises for habitat selection? |
- max resource recovery - minimum risks for higher fitness -increase interactions with other spp (eg. mutualism) |
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how do you measure habitat use and seletion? |
- browse, pellet or track surveys - stomach contents - ground observations via line transects - aerial surveys - aerial surveys IDing marked individuals - relocating marked individuals using VHF, GPS or satellite collars |
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where do you measure habitat use? |
- at location - buffer around location - movement vector - seasonal range |
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what are the different scales for measuring habitat availability or selection? |
1st: largest ecological scale 2nd: second largest (eg. annual range) 3rd: small scale (eg. monthly range) 4th: smallest scale (eg. at location measurements) |
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what is a spp distribution model |
a model that related the distribution of an organism to a set of environmental factors |
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what are the requirements to build a spp distribution model? |
- data describing distr of organism: (quantitative or qualitative) - environmental variables that influence distr: (field observations, remotely sensed data) - modelling framework: presence only spp data, presence-absense spp data, presence-pseudo-absence data, expert knowledge , expert knowledge |
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what is the habitat suitability index? |
- use expert opinion/literature to identify important environmental variables - identify strength or importance of variables -- become weighting coefficients - multiple coefficients for a site to obtain habitat ranking |
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what is the resource selection function? |
- quantitative species distribution model - any math equation that produces the relative prob of occurrence of a pop of animals or plants - nonrandom patterns of distribution suggest selection or avoidance |
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what does resource selection function tell us? |
- statistically defensible relationship between distr of population and environmental features (weighting of coefficients) - maps of habitats likely to be used by the pop |
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assumptions of resource selection studies? |
- selection of random respresentative sample of subjects - animal relocations are independent - availability is estimated correctly and is constant over the period of observation - used resources are classified correctly |
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what are the methods for relating habitat selection to populations? |
- conventional pop estimate based on sample and strata - pop estimate based on RSF probabilities |
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reference area vs extrapolation area? |
reference area: scale density of individuals in reference area by selection for each habitat type; greater selection coefficient means greater proportion of individuals in that habitat extrapolation area: given density of individuals by habitat in reference area, apply to extrapolation area |
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assumptions of habitat based density estimator |
- pop distribution/density is correlated with habitat selection - reference population is at K - individuals in extrapolation area are free to distribute themselves according to habitat quality |
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what are the types of distribution data? |
- habitat use - vital rates |
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what does the andersen gill survival model accomodate? |
- left and right censoring - variation in observation period, discontinuous intervals of risk |
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what explanatory themes are models defined for? |
- demography - human disturbance - habitat |
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what is PATCH? |
- program to assist with the tracking of critical habitat - age/stage structured stochastic pop model - spatially explicit -- requires GIS input: movement parameters, habitat |
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what are spatial processes? |
animals and plants moving from patch to patch |
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what are the dispersal mechanisms? |
- hydrochory: water - anemechory: wind - zoochory: animals - barochory: gravity - antochory: self-dispersal - anthropochory: human activity |
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what are the types of movement between patches/islands? |
- dispersal: colonize habitat; birth site to breeding site - migration: repeated movement among habitat/range |
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why are hexagons used for spatial processes and populations instead of grids? |
allows for 6 different directions of movements instead of 4 |
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what is a metapopulation? |
- population of subpopulations consisting of more than one subpop - represents the interaction of individuals among patches within a matrix of hostile habitats |
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what is a strict Levins' metapopulation |
a metapopulation that requires extinction recolonization events |
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what are the assumptions of a Levins' metapopulation model? |
- density of individuals is unimportant - patch may experience colonisation or extinction event - consider occupancy as a patch containing one or more individuals - population measure: fraction of patches occupied by a spp regardless of density within patch |
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what events will change f in a metapopulation over time? |
- extinction - colonisation |
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what is the rescue effect? |
the reduction in the prob of extinction that occurs when more patches are occupied and since more individuals increase N |
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what are the assumptions of levins' patch occupancy model? |
- homogenous patches: no difference in size or quality - no spatial structure -- extinction and colonisation rates are affected by fraction of occupied sites, not spatial arrangement - no time lags: df/dt responds instantly to f, c and e - constant c and e -- no stochastic forces - only care about patch occupancy, not N |
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what are the positives of metapops? |
- genetic interchange - more resilient to disease, predators, catastrophe, environmental stochasticity - connected pops provide opportunity for rescue effect - based on a theoretic construct |
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what are the antirescue effects/negatives of metapops? |
- source/sink pops -- sink habitats deplete source habitats - connectivity of disease/predators resulted in increased mortality - hostile matrix -- poor survival of dispersers will reduce pop viability |
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what are the different types of interspecific interactions? |
- symbiosis: interaction of two different spp (not negative or positive for either) - predation/parasitism: one benefits at the expense of another - competition: negative interaction for both individuals - commensalism -- one individual benefits from the interaction while the other experiences no benefit or harm - mutualism -- both individuals form a partnership benefitting from the interaction - amensalism: one individual harms another without benefit |
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what is predation and the outcomes? |
- consumption of all or part of one living organism by another - negative interaction for consumed individual and positive for the consumer - increase fitness of predator and other prey in pop (conspecifics) - evolution: prey and predator adapt and evolve to increase/decrease predation - community effects -- facilitate trophic interactions |
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what are the types of predation? |
- herbivory - carnivory - parasitoid: consumption of meat by larvae - parasitism - cannabilism |
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what are conspecifics |
other members of the same population |
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what are the two mechanisms of cannabilism? |
- size structured: eat small young - sexual: eat mate |
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what is apparent competition? what are the steps |
- competition triangle of 2 prey and one predator - one species supports predator and leads to demise of 2nd species apparent but not real competition steps: - first prey exists with second spp: predator - 3rd prey spp enhances predator/parasitoid population - predator/parasitoid depresses/extirpates first, less competitive, spp |
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what are the strategies to avoid predators? |
- colouration - chemical defences - life-history strategies - catalepsis: playing dead so predator ignores - life history strategies: low density make prey for lower rates of encounter - socialisation: many eyes for increased vigilance with less investment per individual; swamping -- high density of prey to disorient predators |
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what are the two behavioural realities that limit predators' ability to consume prey? |
- time required to search for prey - timre for handling prey |
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what are the functional responses of predation rates? |
- type 1: number of prey caught is a linear function of prey density; prey mortality is constant - type 2: predator is overwhelmed by prey and limited by processing time; prey mortality rate decreases with prey density - type 3: predators increase search activity with increasing prey density; predators can regulate pop |
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what are the numerical responses to rates of predation? |
- type 4: predator density increases as a fxn of prey density -- flat linear - type 5: predator density increases as function of prey density -- negative linear slope |
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what are aggregational response? |
- temporary increase in predator density as a function of aggregations of prey |
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what does the lotka-volterra equations of predation do? |
- predict number of prey necessary for predator pop to increase - predict number of predators necessary to control a prey pop - predict the period and amplitude of dependent cycling predator-prey pops - predict the equilibrium condition for predator-prey dynamics |
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what are the numerical outcomes of predation? |
- predators convert prey into fitness units -- more repro and/or survival - prey -- predation results in extreme reduction in fitness of individual prey item - outcome: increase in number of predators and reduction in number of prey to some equilibrium or nonequilibrium point |
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what are the four phases in the predator prey isocline plot? |
- phase 1: predators increase and victims increase - phase 2: predators increase and victims decrease - phase 3: predators decrease and victims decrease - phase 4: predators decrease and victims increase |
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what are the four phases in the predator prey isocline plot? |
- phase 1: predators increase and victims increase - phase 2: predators increase and victims decrease - phase 3: predators decrease and victims decrease - phase 4: predators decrease and victims increase |
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assumptions of the lotka volterra predation model |
- prey exhibit exponential growth -- no density dependence - predator is fully dependent on prey -- 2 spp model - predators can consume and infinite number of prey -- type 1 functional response - no spatial structure to environment -- predation risk is equal across population area |
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what is interspecific competition? |
mutually negative interaction to eliminate one spp |
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what are the categories of interspecific competition? |
- exploitive: through consumption one spp limits resources available and used by a second spp - interference -- behaviourally, one spp actively excludes a second spp from area or resource - pre-emptive: through occupancy of space one spp excludes a second - apparent: tri spp pred-prey dynamic; not competition for resources |
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what are the mechanisms of competition |
- consumptive -- one spp negatively affects another by being the first to consume shared resource - occupancy -- phgysical space/resource is occupied - overgrowth -- one organism overgrows another restricting or removing resources; does not require direct contact - territorial - encounter - chemical |
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how would you test a relationship for competition? |
- experimental: introduce two spp in controlled environment (direct evidence) - ecological release -- two spp demonstrating allopatric distr have broad range, much smaller when sympatric with competitors (indirect evidence) - niche partitioning: two spp have similar ecology but use resources differently - character displacement -- two spp demonstrating allopatric distr have nearly identical physical characteristics; when sympatric -- characteristics diverge - historical replacement: invasive or competitively superior spp replace another spp over time |
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what are the four outcomes of competition? |
- exclusion of species 2 by species 1 - exclusion of species 1 by species 2 - stable equilibrium - unstable equilibrium -- determined by starting point |
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assumptions of the lotka volterra competition model |
- limited resources - competition coefficients constant - linear density dependents - no benefit from consuming competitiors - 2 spp model |
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what is a grinnellian "requirement" niche |
the sum of the habitat requirements that allow a species to reproduce |
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what is an Eltonian "impact" niche |
an animals place in the biotic environment, its relations to food and enemies |
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what is hutchinson's niche? Primary components? |
niche visualised as an n-dimensional hypervolume of resources needed to maintain pop - fundamental/pre-interactive nich - realised post-interactive niche |
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what are the primary components of hutchinson's niche? |
fundamental/pre-interactive niche: resource values where a spp can persist in the absence of competitors/predators realised post-interactive niche: impact of other spp in limiting the range of conditions exploited |
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what are bioclimatic envelopes? |
- area of suitable climate for a spp or community in terms of temp and precipitation |
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what are the problems with bioclimatic envelopes? |
- interaction with other spp - fundamental, not realised nich - works only for organisms constrained by climate |
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what is a food web? |
feeding relations among organisms in all or part of a community |
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what are the weaknesses of food webs? |
- other kinds of interspecific interactions not defined well - simple descriptive devices created to illustrate subsets of important interactions - unable to describe all trophic interactions |
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what are the types of food webs? |
- source web: describe feeding relationships that start at a single source start at beginning point - sink web: describe relationship mong spp from the perspective of the consumer -- start at end point - community web: describe the entire set of feeding relatioships (difficult) |
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what evidence is there of food web dynamics? |
- experimental - static models describe food web structure - dynamic models describe predator prey and competition - new dynamic models -- complex systems approach |
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what are the general patterns in food webs |
- small organisms/primary producers more diverse and abundant than predators - species diversity and abundance decrease as food web progresses - scale is important in understanding food web dynamics - chans are longer in more productive environments - complexity can decrease or increase food web stability - strength of interaction varies - food web patterns vary with time - omnivores are different |
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what are the two types of interspecific effects in food webs? |
direct effect: donor directly interacts with a receiver through competition directly affecting receiver spp
indirect effect: influence of one spp; donor is transmitted through a second spp (transmitter) to receiver spp |
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what are top down vs bottom up effects in food webs? |
- top down: predators dictate composition and abundance of spp in lower trophic levels - bottom up: primary producers productivity dictates abundance and diversity of community |
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what is a trophic cascade? |
top-down effects of predators on lower levels |
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what are tri-trophic effects? |
indirect effects that propagate from the bottom up through multiple trophic levels |
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what are species level changes in community composition? |
- intraspecific competition - interspecific competition - predator/prey/parasitism/disease - commensalism - mutualism |
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what are community/ecosystem level change? |
- reduction or increase in nutrients or energy input - changes in global patterns or variablility of climate - natural disturbance - anthropogenic disturbance |
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what is succession? |
the phenomenon of temporal change in species composition following natural or anthropogenic disturbances |
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what are the types of succession? |
- primary: occurs on sites without existing vegetation - secondary: occurs on sites with established vegetation |
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what are the explanations of succession? |
- facilitation: established spp alter conditions so they are more suitable for next set of spp - tolerance: least tolerant/competitive spp leave first resulting in community of most competitive spp --> intensity of competition increases over time - traits and gradients: species establishment and persistence dependent on gradient of tolerance to limited or limiting resources - inhibition and initial floristic composition: community defined by initial plant colonisers and succession dictated by colonisers - state and transition models: community has multiple stable states dictated by type and intesity of disturbance - stochastic effects: finite number of community states |
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what is the intermediate disturbance hypothesis? |
- disturbance prevents competitively dominant spp - allows coexistance of climax and colonist spp - richness maximised by disturbance of intermediate frequency and intensity |
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what is a markov chain? |
calculations in a chain to determine proportion of species after succession |
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assumptions of markov chain? |
- communities can be represented as finite number of states - transition probabilities are constant over time and space - transition determined by the immediately previous state, no other factors further in the past - no time lags - density independent model |
