52 Flashcards
population ecology
study of populations in relation to the environment
dispersion
pattern of spacing among individuals within the boundaries of the population
uniform dispersion pattern may result from
direct interactions btwn individuals in the population
why do some plants exhibit uniform dispersion pattern
they secrete chemicals that inhibit the germination and growth of nearby individuals that could compete for resources
animals often exhibit uniform dispersion b/c of
antagonistic social interactions, ex territoriality
territoriality
the defense of a bounded physical space against encroachment by other individuals
__ dispersion pattern not as common in populations as __ pattern
uniform; clumped
3 factors that influence pouplation density and dispersion patterns
ecological needs of a species, environmental sturcture, interactions btwn individuals within the population
demography
study of the vital statistics of populations and how they change over time
life tables
age-specific summaries of the survival pattern of a population
cohort
group of individuals of the same age
best way to construct a life table
follow the fate of a cohort from birth until all are dead
to build the life table, we need to determine
# of individuals that die in each age group; proportion of cohort surviving from one age to the next
survivorship curve
graphic way of representing data in a life table; plot of proportion of numbers in a cohort still alive at each age
animals that exhibit type I survivorship
humans and large mammals that produce few offspring but provide them w/ good care
what type of animals exhibit type III and 3 examples
those that produce very large numbers of offspring but provide little or no care; ex long-lived plants, fishes, marine invertebrates
examples of type II organisms
belding’s ground squirrels, other rodents, various invertebrates, some lizards, some annual plants
describe bird surivorship
high morality among young (type 3), constant mortality among adults (type 2)
describe invertebrate survivorship
“stair-stepped” curve. brief periods of increased mortality during molts, followed by periods of lower mortality when exoskeleton is hard
in populations without immi/emigration, which 2 factors determine population trends
survivorship, reproductive rate
reproductive table aka
fertility schedule
reproductive table is an
age specific summary of the reproductive rates in a population
best way to construct fertility schedule
measure reproductive output of a cohort from birth til death
reproductive output for sexual species is
the produce of the proportion of females of a given age that are breeding and the number of females of a given age that are breeding and the number of female offspring of those breeding females
life history
traits that affect an organism’s schedule of reproduction and survival
life histories entail 3 basic variables:
when reproduction begins, how often the organism reproduces, how many offspring are produced during each reproductive episode
big bang reproduction aka
semelparity
big-bang reproduction
produce thousands of offspring in a single reproductive opportunity, then dies (parent)
2 organisms big bang reproduction
salmon, agaves
repeated reproduction aka
iteroparity
iteroparity
several reproductive episodes, only a few offspring per episode
in what environment is iteroparity more favorable
dependable environments where competition for resources may be intense
in what environment is semelparity more favorable
low survival rate of offspring, as in highly variable or unpredictable environments
K-selection
selection for life history traits that are sensitive to population density; density-dependent selection
r-selection
selection for life history traits that maximize reproductive success in uncrowded environments (low densities); density-independent selection
K-selection tends to maximize poopulation size and oprates in populations living at
carrying capacity
r-selection tends to maximize
r, the rate of increase
r-selection occurs in environments in which
population densities will fluctuate well below carrying capacity or inidivudlas are likely to face little competition
in many bird populations. ____ is a good indication that territoriality is restricting population growth
presence of surplus (nonbreeding) individuals
