Organisms and the abiotic environment

Organisms and the abiotic environment The Red River Pupfish, Cyprinodon rubrofluviatilis

Organisms and the abiotic environment red creek Cyprinodon rubrofluviatilis

Organisms and the abiotic environment

Organisms and the abiotic environment broad tolerance for environmental conditions: temperature (eurythermal) salinity (euryhaline) oxygen concentration (euryoxic)

Organisms and the abiotic environment

Organisms and the abiotic environment The Southern Redbelly Dace, Phoxinus erythrogaster

Organisms and the abiotic environment Phoxinus erythrogaster the Blue River

Organisms and the abiotic environment

Organisms and the abiotic environment narrow tolerance for environmental conditions: temperature (stenothermal) salinity (stenohaline) oxygen concentration (stenoxic)

Distribution and abundance of organisms A species’ tolerance for abiotic environmental conditions is one factor that affects its distribution and abundance

Distribution and abundance of organisms Some species are widespread and common

Distribution and abundance of organisms Other species are localized and rare ‘akiapola’au the Rich Mountain salamander

Distribution and abundance of organisms The distribution and abundance of species changes over time Some species decline in abundance and extent of geographic range

Distribution and abundance of organisms The distribution and abundance of species changes over time Other species increase in abundance and expand in range

Distribution and abundance of organisms The causes of these changes include… geological change climate change change in the biotic environment “anthropogenic” factors

Population ecology Ecologists are concerned with how population size changes… All populations have the capacity to increase in size This capacity is the “biotic potential” of the population and with the factors that regulate change through reproduction by the individuals in the population

Population ecology Biotic potential is the rate at which a population would grow with no limitation on resources and no mortality due to predation or other factors Under these conditions populations grow exponentially…

Population ecology Exponential population growth: Change in population size over time is a function of the current population size and the biotic potential of the population

Population ecology dN/dt = r N as time passes, more individuals are added to the population number of individuals added is a function of the population size

Population ecology dN/dt = r N with no constraints, a population grows exponentially

Population ecology But there are constraints… food, space, nest sites, etc become limiting intraspecific competition for resources slows population growth

Population ecology the populaiton size that the resources of a habitat can support is the “carrying capacity”

Population ecology dN/dt = r N(K-N/K) Where K is the carrying capacity

Population ecology dN/dt = r N(K-N/K) What happens to dN/dt when N is small relative to K?

Population ecology dN/dt = r N(K-N/K) What happens to dN/dt as N approaches K?

Population ecology “Logistic” population growth

Population ecology What factors regulate population growth? Density-dependent factors: intraspecific competition

Population ecology What factors regulate population growth? Density-dependent factors: intraspecific competition predation

Population ecology What factors regulate population growth? Density-dependent factors: intraspecific competition predation disease and parasitism

Population ecology What factors regulate population growth? Density-independent factors: weather; drought, flood, storm, heat, cold

Population ecology What factors regulate population growth? Density-independent factors: weather; drought, flood, storm, heat, cold catastrophes

Life history strategy Population growth depends on reproduction by individuals in the population Natural selection acts on characteristics that affect the balance between “somatic growth” and “reproductive growth” over the lifespan of individuals. The balance between “somatic growth” and “reproductive growth” over the lifespan of individuals is “life history strategy”

Life history strategy There are two extremes in the spectrum of life history strategy…

Life history strategy There are two extremes in the spectrum of life history strategy… “r” selected species emphasize biotic potential, the ability to increase in population size quickly

Life history strategy There are two extremes in the spectrum of life history strategy… “r” selected species emphasize biotic potential, the ability to increase in population size quickly “K” selected species emphasize stable population size, at or near K

Life history strategy “r” selected species… high intrinsic rate of increase small body size (usually) rapid ontogenetic development early reproductive maturity large numbers of small offspring short life span poor competitors for space, light… highly variable population size often density independent regulation of population size often inhabit variable, unpredictable, or disturbed habitats good dispersal and colonizing capabilities

Life history strategy “K” selected species emphasize stable population size, at or near K

Life history strategy “K” selected species… low intrinsic rate of increase large body size (usually) slow ontogenetic development late reproductive maturity small numbers of large offspring long life span good competitors… stable population size, near K often density dependent regulation of population size often inhabit stable, predictable, or undisturbed habitats population size at equilibrium