53: Population Ecology Flashcards
what affects the size of a population and how it changes over time
adding or removing individuals
what can be used to describe population
its boundaries and size
what is a boundary
it can be natural like an island or lake
or arbitrarily defined by an investigator
what is population ecology
explores how biotic and abiotic factors affect population, density, dispersion and demographics
what is density
the number of individuals per unit area or volume
what is dispersion
pattern of spacing among indiviudals within the boundaries of the population
what is demography
study of birth/death/migration rates
what can be used to find density
sampling techniques like the mark-recapture method
how do they use the mark-recapture method
scientists capture and tag random sample of individuals in a population and they are given back to the population then they capture a second sample and note how many they mark
what is the formula to solve for population size
x/n= s/N or N=sn/x
what is density the result of
processes that add individuals and remove individuals
what is immigration
influx of new individuals and births to increase population size
what is emigration
movement of indivduals out of a population, and deaths to decrease population size
what is the pattern of dispersion determined by
spacing among individuals within the boundaries
what factors affect the spacing of individuals in a population
environmental and social factors
what is the most common pattern of dispersion
clumped
what is a clumped pattern
- individuals aggregate in patches
- aggregate in high resource availability or favorable physical conditions
what else can influence the clumped pattern
mating behavior and group predation or defense
what is uniform dispersion
individuals spread out evenly
in uniform dispersion what do plants do
secrete chemicals that inhibit germination and growth of competing individuals
what is uniform dispersion influenced by
social interactions like territory and the defense of a bounded space against other individuals
what is random dispersion
the position of each individuals is independent of other individuals
when does random dispersion occur
occurs in the absence of strong attractions or repulsions among individuals
what is demography
study of the vital statistics of population
what is a life table
age-specific summary of the survival and reproductive rates
what is the fate of a cohort on the life tables
a group of individuals of the same age
what group is ignored in a life table
males because only females produce offspring
what does a life table show
proportions of females alive at each age and the number of female offspring produced per female
what is survivorship curve
graphic way of representing the data in a life table
what are the general types of survivorship curves
type 1
type 2
type 3
type 1 curve
low death rates in early and middle
increase in death rates among older age groups
type 2 curve
constant death rate over organisms life span
type 3 curve
high death reates for the young and lower death rate for survivors
what can be used to estimate the number of breeding females
direct counts, mark-recapture, molecular tools
what is an exponential model
describes population growth in an idealized unlimited environment
population growth for an exponential model
dN/dt = rN r = per capita change dN/dt = very small changes in population size over short
what are some characteristcs of a J-shaped curve
rate of increase is constant
large populations grow faster than small populations
- larger r grows faster
-smaller r = grows slower
what does the logistics model describe
describes how a population grows more slowly as it nears its carrying capacity
wha is carrying capacity
the max pop size that an enviornment can sustain
what are some characteristics of the logistics population growth model
- starts with exponential growth model
- adds (K) carrying capacity
- k reduces per capita
- new individuals are added to the population most rapidly at intermediate population sizes
- population growth decrease as N approaches K
what is the logistics pop formula
dn/dt = rn(K-N)/k
what shape does a logistics growth model represent
sigmoid(s shape)
-
what is the logistics model used for
predicting the rate of recovery for small populations
- estimating the sustainable harvest rates for wildlife
- estimating the critical size
what is the life history?
traits that affect the schedule of reproduction and survival
what does life history reflect
the development, physiology and behavior of an organism
what does life-history entail
the age, how often they reproduce, how many offspring are produced
what is semelparity
reproduce once or big band reproduction then die
what is iteroparity
repeated reproductive events
what influences trade-offs
selective pressures influence the number and size of offspring
what do species do when they have young who don’t have a long life span
produce many small offspring
plants produce a large number of small seeds
ensure that at least some of them will grow and eventually reproduce
why do parents produce few offspring
invest more energy in each offspring to increase the probability of survival for each
what is density-dependent birth and death rates
example of negative feedback that regulates population growth
what affects density-dependent birth and death rates
competition for resources, disease, predation, territoriality, toxic wastes, and intrinsic factors
what is the intrinsic factor
the genetic, physiological, and pathological characteristics of an individual
