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Wright BIO 1150 - Population
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BIO 115 1st Edition Lecture 31 Topic Discussed: PopulationDynamic biological processes influence population density, dispersion, and demographics- Population- group of individuals of one species living in same areao described by their boundaries and size- Population ecology - study of populations in relation to their environmento Includes: environmental influences on density/distribution, age structure, and population sizePopulations- Density -number of individuals per unit area or volume- Dispersion-the pattern of spacing among individualsPopulation- can be estimated by extrapolation from small samples (quadrats or transects for plants), an index of population size (number of nests), or the mark-recapture methodMark-recapture method- capture, tag, and release a random sample of individuals (s) in a population- capture a second sample of individuals (n), and note how many of them are marked (x)- Population size (N): N= sn/xPopulation sizes and density- Immigration - the influx of new individuals from other areas- Emigration – leaving a populationThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.- And births and deathsPatterns of DispersionEnvironmental and social factors influence the spacing of individuals in a population- clumped dispersion-individuals aggregate in patcheso result of resource availability and behavior- uniform dispersion-evenly distributedo result of territoriality, the defense of a bounded space against other individuals- random dispersion- the position of each individual is independent of other individualso occurs in the absence of strong attractions or repulsionsallopathy-chemical inhibition of neighborsDemographics- study of the vital statistics of a population and how they change over time- Death rates and birth rates are of particular interest to demographersLife Tables- A life table- age-specific summary of the survival pattern of a population- It is best made by following the fate of a cohort- Cohort- group of individuals of the same age- Can calculate proportion alive, death expectancy etc. with survivorship curve- Type I-high survival rate at beginning of life and low at end- Type II-consistent survival rate throughout life- Type III- low survival rate at beginning and high at endReproductive Rates- species with sexual reproduction-demographers often concentrate on females in a population- reproductive table (fertility schedule)- age-specific summary of the reproductive rates in a population The exponential model describes population growth in an idealized, unlimited environment- useful to study population growth in an idealized situation to understand the capacity of species to increase and the conditions that may facilitate this growthPer Capita (per head) Rate of Increase- If immigration and emigration are ignored, a population’s growth rate (per capita increase) equals birth rate minus death rateThe population growth rate : (∆N/∆t)=B-D- ∆N is the change in population size- ∆t is the time interval- B is the number of births- D is the number of deathsBirths and deaths can be expressed as the average number of births and deaths per individual during the specified time interval- B =bN- D= mN- b = annual per capita birth rate- m(for mortality) =per capita death rate- N = population sizeper capita rate of increase (r): r=b-mZero population growth (ZPG) occurs when the birth rate equals the death rate (r= 0)Change in population size can now be written as: ∆N/∆t=rNInstantaneous growth rate: dN/dt= rintsN- rinst = instantaneous per capita rate of increaseExponential Growth: dN/dt=rmaxN- Exponential population growth- population increase under idealized conditions- Rmax= the rate of increase is at its maximumThe logistic model describes how a population grows more slowly as it nears its carrying capacity- Exponential growth cannot be sustained- Carrying capacity (K)-maximum population size the environment can supporto varies with the abundance of limiting resourcesThe Logistic Growth Model: dN/dt=rmaxN (K-N)/K- per capita rate of increase declines as carrying capacity is reachedstarts with the exponential model and adds an expression that reduces per capita rate of increase as N approaches


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Wright BIO 1150 - Population

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