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126 Cards in this Set
- Front
- Back
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Population
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a group of individuals of a single species living in the same space
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All population share...
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3 characteristics:
-distribution -density -abundance |
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Distribution
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the distribution of a population includes the size, shape, and location of the area it occupies
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Density
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the number of individuals per unit area
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Abundance
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the total number of individuals, or biomass, of a species in a specified area
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small scale
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small distances where there is little environmental changes
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large scale
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areas where there is a lot of environmental change
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random population
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when individuals in a population have an equal chance of living anywhere within an area, neutral interactions occur
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regular population
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when individuals live uniformally spaced, antagonist interactions, depletion of resources
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clumped population
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when individuals are more likely to be found in the same areas as others, caused by attraction between individuals, or attractions to a common resource, social organisms are clumped
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rare species are more vulnerable to...
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extinction than common species, have combinations of extensive vs. restricted geographic range, broad vs. narrow habitat tolerance, large vs. small population size
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geometric population growth
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successive generations differ in size by a constant ratio
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exponential growth
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continuous population growth in an unlimited environment, dN/dt = rmaxN
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logistic population growth
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as resources are depleted, population rate slows and eventually stops, incorporation of environmental limitations
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carrying capacity
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(K), the population size when growth stops, birth rates = death rates, growth=0, dN/dt = rmaxN (1-N/k)
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limits to population growth
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the environment limits population growth by changing birth and death rates, includes density dependent and independent factors
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density dependent factors
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biotic factors that effect density, ex. disease and predation
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density independent factors
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abiotic factors that effect density, ex. floods, extreme temperatures
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on large scales, individuals within a population are...
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clumped, drawn to a common resource or for mating, etc.
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population declines with...
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increasing organism size
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geometric and exponential growth
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in the presence of abundant resources, populations can grow at geometric and exponential rates
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geometric/discrete time growth
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-used for any population with pulsed reproduction
-successive generations differ in size by a constant ratio -uses lambda |
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λ
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the geometric rate of increase, the ratio of the population size at two points in time, gives the change in population between two points in time
λ = Nt+1/Nt, can be used when generations overlap |
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to determine population size in the future...
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use Nt=N0λ^t N0=initial popn, t= number of time intervals or generations, Nt= number of indivs at time, t
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pulse of offspring/discrete breeding season
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occurs in annual organisms (lives one year or less), reproduces in one clump, or animals with a set breeding system (birds, amphibians, some fish, some mammals - have overlapping generations)
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λ = 1-d+b (+i-e)
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b= # births/Nt, d= #deaths/Nt, λ=survivors-d+b (+immigrants-emigrants)
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λ>1, λ=1, λ<1
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when λ>1, popn increasing, λ=1, popn stable, λ<1, popn decreasing
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exponential/continuous growth
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in an unlimited environment, continuous growth can be modeled as exponential popn growth, using dN/dt=rmaxN
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rmax
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instantaneous rate of growth, intrinsic rate of popn increase, shows how quickly popn can grow under ideal conditions
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rmax>0, rmax=1, rmax<0
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when rmax>0, popn increasing, rmax=0, popn stable, rmax<0, popn decreasing
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when popn size increases, N, dN/dt...
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...gets larger, because rmax is being multiplied by larger and larger numbers
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to calculate popn size at a specific time, t: (continuous growth)
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Nt=N0e^rmax^t, N0=initial number of indivs., e= base of natural logarithms, t-time in time intervals
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logistic population growth
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as resources are depleted, popn growth rate slows and eventually stops, creates a sigmoidal/s-shaped curve
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in logistic popn growth, the popn ceases at...
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...carrying capacity (k)
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carrying capacity, k
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the number of individuals of a particular popn that the environment can support, birth rates must equal death rates => no growth
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four models of discrete-time popn growth
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1. monotonic damping
2. damped oscillations 3. stable limit cycles 4. chaos |
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monotonic damping
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an s-shaped model of popn growth, population increases rapidly, slows, and ceases at k, rmax>1
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damped oscillations
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population rapidly increase, overshoots and undershoots k and then settles off at k, 1<rmax<2
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stable limit cycles
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popn increases rapidly, cycles between overshooting and undershooting k, alternates between two population size
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chaos
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erratic popn growth and decline, rmax>2.8
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time lag
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when the popn overshoots k, it uses up resources, the births occurring in one lump and there is a sudden reaction to the lack of resources, always one year, ex: moths
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the logistic model accounts for...
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...patterns of growth shown by populations as they begin to deplete resources
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logistic equation
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dN/dt=rmaxN(1-K/N) or (K-N/K), as the size of N gets closer to K, environmental factors increasingly impede further popn growth
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the environment limits popn growth by changing...
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birth and death rates
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density-dependent factors
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biotic factors which limit popn growth, ex. disease, predation, resources, food, shelter, density of mates, anything that affects a fixed number of individuals
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density-independent factors
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abiotic factors that limit popn growth, like storms, high temps, anything that affects a fixed fraction or percentage of the population
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community
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an association of interacting species inhabiting some defined area
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community structure
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includes the number of species, the relative abundance of species, and the kinds of species comprising a community
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guild
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a group of organisms that all make their living in a similar way, ex: fruit eating birds in the rain forest
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species abundance
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most species are moderately abundant, few are very abundant or extremely rare (lognormal distribution)
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species diversity
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a combination of the number of species and their relative abundance
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species diversity is defined by two factors
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1. the number of species in the community (species richness)
2. the relative abundance of species (species evenness) |
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Shannon-Wiener Index
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helps determine species diversity,
H'= -Σ pi loge pi, H'=value of S-W index, pi=proportion of each species, loge=the natural log of pi, s=the number of species in the community |
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rank-abundance curves
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plots the relative abundance of species against their rank in abundance, to make: determine each H', rank, plot proportion, pi, against rank
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species diversity is higher in...
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...complex environments
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character displacement
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process of evolution toward niche divergence due to interspecific competition, causes directional selection
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character displacement and niche shifts reduce the strength of...
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competition, competition can be a strong selective force
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Lotka-Voltera equation
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comparing interactions of two species on each other, ex. species a and b dN/dt=rmaxN(K-N/K), N1=K1/α12, N2=K2/α21
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factors that prevent popn explosion
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-conditions change yearly, λ is not constant, rmax is ideal but doesn't always occur
-disease -predation increase with popn increase -big die-offs, recoveries, etc. -disturbance can decrease a popn, when it recovers, disturbance prevents excessive growth -density-dependence, competition for resources increases as popn size increases, birth and death rates change as popn changes |
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intraspecific competition is central to density-dependence, why?
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density-dependent populations are reliant on resources like food, shelter, etc. and must compete between other species as well as individuals of their own population to get these resources
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reproductive effort
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the allocation of energy, time, and other resources to the production and care of offspring, usually requires trade-offs
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r selection
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selection favoring a higher population growth rate
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k selection
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selection favoring more efficient utilization of resources such as food and nutrients, these species hand out around carrying capacity most of the time (stable environments)
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Pianka's life history model says...
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most organisms lie between these types of selection and incorporate traits of both r and k, r species (survivorship III), k species (survivorship I and/or II)
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semelparity
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reproduction will occur in one event and many offspring will be produced (annual plants, salmon)
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iteroparity
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repeated reproduction,several reproductive periods throughout the organism's life span
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ruderals
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plants that live in disturbed habitats, disturbance may help in competition with other plants
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Grime's Triangle
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gives four experimental extremes (modeled after plants)
1. low-disturbance, low-stress 2. low-disturbance, high-stress 3. high-disturbance, low-stress 4. high-disturbance, high-stress stress: environmental conditions which limit growth disturbance: limit plants by destroying biomass |
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stress-tolerant plants
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live in conditions of high stress and low disturbance, grow slowly, conserve resources, exploit temporary favorable conditions
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competitive plants
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live in low-disturbance-low-stress environments
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Opportunistic, Equilibrium, and Periodic Life Histories (Winemiller and Rose)
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-opportunistic- low juvenile survival, low numbers of offspring, early reproductive maturity, maximize colonizing ability (guppies
-periodic- low juvenile survival, high numbers of offspring, late maturity (sunfish) -equilibrium- high juvenile survival, low numbers of offspring, later reproductive maturity (sharks) |
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survivorship curves
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summarize the pattern of survival in a population, types I, II, and III, most species don't fit these patterns, they simply set boundaries
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type I
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high juvenile survival, high survival for middle age, high mortality in the aged
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type II
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constant rates of survival
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type III
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high mortality in young followed by a relatively high rate of survival
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life tables
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bookkeeping that lists survivorship and death in populations estimating patterns of survival, two types: cohort and static
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cohort life table
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uses individuals born at the same time
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static life table
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uses individuals born at different times, gives a snapshot of survival within a short time period
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age distribution
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the proportion of individuals of different ages within a population
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birthrate
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the number of young born per female in a period of time, ex. number of eggs laid or seeds produced
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fecundity schedule
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the tabulation of birth rates for females of different ages in a population
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net reproduction rate (R0)
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average number of offspring/individual in lifetime or generation
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stable age distribution
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assumes that birth and death rates of each age group are constant
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interference competition
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direct aggressive interaction between individuals
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resource limitation
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limited supply of suitable space for territories
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intraspecific competition
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competition between members of the same species
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interspecific competition
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competition between individuals of different species, reduces the fitness of both
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alleopathy
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the release of toxins by a stationary organism (usually plants) to kill off competitors
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population effects of competition
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both species decrease in population, one is winning but must use more energy/resources to do so = fewer babies, one is losing and has less access to resources=fewer babies
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resource partitioning
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splitting up resources between two or more competitors or former competitors
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niche shift vs. niche expansion
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reduction in space vs. increase in space
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competitive release
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increase in population size with loss of a competitor, often due to niche expansion toward the fundamental niche
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unstable coexistance
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doesn't really involve coexistance, one species wins (depending on starting conditions)
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competitive exclusion
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one species out-competes the other and leads them to extinction
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priority effect
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competitive interaction where the species that gets there first wins
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competitive coexistance
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the two competitors coexist but there will ALWAYS be competition between them for resouces
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exploitative competition
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one species takes as much of resource as they can before the other does, ex. plate of cookies
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inferior vs. superior competitors
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competitor that does not do very well vs. the competitor that does better, these can coexist or the superior will out-compete the inferior
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an invading species will move into what kind of niche?
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a new species should come into an unused niche, where it has a better chance of surviving, this will cause niche shifts in the natives, decreasing population in these groups due to increased competition
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to determine if your plane diagram shows competitive coexistance...
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draw growth arrows, if the 'average direction' arrows in the overlapping triangles point towards each other, competitive coexistance is occurring.
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limiting similarity
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the limit to how similar two species can be and still coexist, to determine this, use the Lotka-Volterra equation
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when is it most appropriate to use a life table?
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when the population of interest is new and small and they haven't use up all the resources yet
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R0
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the sum of all fecundity for all ages for a generation
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nx
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the number surviving at the start of age x
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lx
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the proportion surviving at the start of age x
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dx
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the proportion dying at age x
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qx
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the age specific mortality rate
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Fx
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the total births in a cohort at age x
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mx
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the age specific birth rate per individual in the population/per capita
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lxmx
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the realized fecundity
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R0=λ when...
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the species is annual, generation time is only one year
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generation time
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T=Σ(x)lxmx/Σlxmx, where x=age, lxmx=realized fecundity for that age, gives the time between when the mother is having her babies and when her daughter is having her babies
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axes on survivorship curves
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y=log number of survivors, x=time
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annual species
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a species that goes through entire life cycle in one year with only one generation per year
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perennial species
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lives for more than one year, in plants, the vegetation above ground might be different year to year but the bulbs/roots are the same
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fecundity
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reproduction per individual (number of births in a litter)
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in a discrete time growth model, where can r and k species be found?
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r species are found in the fast growth portion of the s-curve, k species hang out around equilibrium
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per capita rate of increase, r
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r= lnR0/T
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r characteristics
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small body size, many offspring, early reproductive maturity, fast development, short lifespan, poor competitors disturbance adapted, low juvenile survival, semelparous
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k characteristics
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large body size, few offspring, late reproductive maturity, slow development, long lifespan, good competitors, stable habitats, stable popn size, high juvenile survival, iteroparous
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ln(lambda)=...
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rmax!
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fundamental niche
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the habitat in which an organism might live in the absence of other species
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realized niche
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the actual niche of a species where distribution is limited by biotic interactions like disease, competition, predation, and parasitism
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life history
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adaptations of an organism that influence aspects of its biology, such as number of offspring produced, survival, and size and age at reproductive maturity
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niche
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summarizes environmental factors that influence the growth, survival, and reproduction of a species
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in logistic growth, dn/dt slows as population...
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increases because the difference between (1-N/K) gets smaller (as it approaches K), when N=K, the right side of the equation becomes zero
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