53.1-5

53.1-5

define population ecology
the study of population in relation to their environment, including environmental influences on population density and distribution, age structure, and variation in population size
dynamic biological processes influence ________________
population density, dispersion, and demographics
define population
a group of individuals of the same species that live in the same area and interbreed, producing fertile offspring
define density
the number of individuals per unit area or volume
changes as individuals are added to or removed from a population
define dispersion
the pattern of spacing among individuals within the boundaries of a population
what is the mark-recapture method?
a sampling technique used to estimate the size of wild animal populations
how do population ecologists estimate density?
from number of nests, burrows, tracks, fecal droppings
define immigration
the influx of new individuals into a population form other areas
define emigration
the movement of individuals out of a population
what are the patterns of dispersion within a population’s geographic range?
clumped
uniform
random
clumped dispersion
the most common pattern
where individuals are aggregated in patches
plants and fungi are often clumped where factors favor germination and growth
uniform dispersion
evenly spaced pattern of dispersion
may result from direct interactions between individuals in the population, such as territoriality
define territoriality
a behavior in which an animal defends a bounded physical space against encroachment by other individuals, usually of its own species
random dispersion
unpredictable spacing
the position of each individual in a population is independent of other individuals
occurs in the absence of strong attractions or repulsions among individuals or where key physical or chemical factors are relatively constant across the area
ex: plants by windblown seeds
define demography
the study of changes over time in the vital statistics of populations, especially birth and death rates
uses life tables and survivorship curves
define life table
an age specific summary of the survival pattern of a population
what is the best way to construct a life table?
to follow the fate of a cohort
define cohort
a group of individuals of the same age in a population
define survivorship curve
a plot of the number of members of a cohort that are still alive at each age
one way to represent age specific mortality
three types: type I, II, III
type I survivorship curve
flat at the start, reflecting low death rates during early and middle life, and then drops steeply as death rates increase among older age groups
many large animals including humans that produce few offspring but provide good care
type III survivorship curve
drops sharply at the start, reflecting very high death rates for the young, but flattens out as death rates decline for those few that survive the early period of die off
usually organisms that produce large amounts of offspring but provide little to no care, such as long lived plants, fishes, and marine invertebrates
type II survivorship curve
intermediate, with constant death rate over the organisms life span (straight line)
squirrels, rodents, annual plants
define reproductive table
an age specific summary of the reproductive rates in a population
the exponential model describes ___
population growth in an idealized, unlimited environmnet
what are population ecologist most interested in?
the difference between the per capita birth rate and per capita death rate, which is the per capita rate of increase
define zero population growth(ZPG)
a period of stability in population size, when additions through population through births and immigration are balanced by subtractions through deaths and emigration
define exponential population growth
growth of a population in an ideal, unlimited environment, represented by a j-shaped curve when population size is plotted over time
assumes resources are unlimited with unlimited reproduction
the j-shaped curve of exponential growth is characteristic of ___
some populations that are introduced into a new environment or whose numbers have been drastically reduced by an event and are rebounding
the logistic model describes___
the logistic model describes how a population grows more slowly as it nears its carrying capacity
define carrying capacity
the maximum population size that can be supported by the available resources, symbolized as K
what are some limiting factors of carrying capacity?
energy
shelter
refuge from predators
nutrient availability
water
suitable nesting sites
define logistic population growth
population growth that levels off as population size approaches carrying capacity
the per capita rate of increase approaches zero as the carrying capacity is reached
produces a sigmoid(S-shaped) growth curve when N(population size) is plotted over time
life history traits are products of _________
natural selection
define life history
the traits that affect an organisms’s schedule of reproduction and survival
what are the three main variables of life history?
when reproduction begins
how often the organism reproduces
how many offspring are produced per reproductive episode
define semelparity
reproduction in which an organism produces all of its offspring in a single event; also known as big band reproduction
example: salmon and agave plant
define iteroparity
reproduction in which adults produce offspring over many years; also known as repeated reproduction
produce few but large offspring
what are the two critical factors between selemparity and iteroparity?
survival rate of the offspring and the likelihood that the adult will survive to reproduce again
when survival rate of offspring is low, semelparity is favored because adults are also less likely to survive in such environments
iteroparity is more favorable in dependable environments, where adults are more likely to survive to breed again and where competition for resources may be intense
define K-selection
selection for life history traits that are sensitive to population density; also called density dependent selection
favored at high density
define r-selection
selection for life history traits that maximize reproductive success in uncrowded environments; also called density independent selection
many factors that regulate population growth are ____________
density dependent
density independent
referring to any characteristic that is not affected by population density
ex: a birth or death rate that does not change with population density
density dependent
referring to any characteristic that varies with population density
acts as a negative feedback between population density and rates of birth and death
ex: death rate that rises as population density rises
what are the mechanisms of density dependent regulation?
competition for resources
predation
intrinsic factors
toxic wastes
territoriality
disease
how does competition for resources affect population growth?
increasing population density intensifies competition for resources, reducing reproductive rates
how does predation affect population growth?
can be important if a predator captures more food as the population density of the prey increases
predators may feed preferentially on that species if population builds up
how do intrinsic factors affect population growth?
intrinsic physiological factors sometimes regulate population size
reproduction may drop at high population densities
how do toxic wastes affect population growth?
organisms produce wastes, and too much waste is toxic
how does territoriality affect population growth?
territoriality can limit population density when space becomes the resource for which individuals compete
maintaining territory increases likelihood that animal will capture enough food to reproduce
surplus means territoriality is restricting population growth
how does disease affect populate growth?
diseases have a higher transmission rate in higher crowded areas
define population dynamics
the study of how complex interactions between biotic and abiotic factors influence variations in population size
define metapopulation
a group of spatially separated populations of one species that interact through immigration and emigration