Chapter 53 Flashcards
what is density?
density is the number of individuals per unit area or volume
what is dispersion?
dispersion is the pattern of spacing among individuals within the boundaries of the population
immigration vs emigration
immigration is influx of individuals from other areas
emigration is movement of individuals out of a population
what happens in a clumped dispersion?
individuals aggregate in patches, may be influenced by resource availability and behavior (starfish, wolves, fish)
what is a uniform dispersion?
in a uniform dispersion, individuals are evenly distributed (usually applies to birds on land when they are spread out)
does territoriality apply to uniform dispersion or clump dispersion?
both uniform and clump dispersion can be influenced by territoriality, but not in random dispersion
what is random dispersion?
random dispersion is the position of each individual being independent of other individuals, so mainly in plants, sexual structures dont know where they land
what is a survivorship curve?
a survivorship curve is a graphic way of representing the data in a life table,
what three types are survivorship curves classified into?
- type 1: low death rate in early life, but increase among elders (humans)
- type 2: constant death rate over life span (squirrels)
- type 3: high death rate for young and low death rate for survivors (oysters)
what is exponential population growth and the equation?
exponential population growth is population increase under idealized conditions, rate of increase is at its maximum
- dN/dt = r(inst)N
- J shaped curve, rate of increase is constant, more individuals when time is large
what is carrying capacity (K)?
carrying capacity is the maximum population size the environment can support
can exponential growth be sustained?
exponential growth cannot be sustained for long in any population
what is the logistic population growth model? equation?
the logistic population growth model, the per capita rate of increase declines as carrying capacity is reached, starts with exponential but adds an expression that reduces per capita rate of increase as N approaches K
- dN/dt = r(inst)N (K-N)/K
How do you interpret the (K-N)/K
- When N is small compared to K, the expression is close to 1 and the per capita rate of increase approaches the maximum
- When N is large compared to K, the expression is close to 0 and the per capita rate of increase is small
- When N is equal to K, the population stops growing (Zero population growth)
What happens in species that exhibit semelparity?
they reproduce once and die
What happens in species that exhibit iteroparity?
they produce offspring repeatedly
What is K selection?
K selection, aka density-dependent, selects life history traits that are sensitive to population density
(produce a little offspring so they can take care of them well and make them suitable for life)
What is R selection?
R selection, aka density-independent selection, selects for life history traits that maximize reproduction
(produce a lot of offspring so some survive)
what happens with birth and death rates in density independent (R selection)?
birth and death rates do not change with population density
what happens with birth and death rates in density dependent (K selection)?
in density dependent, birth rates fall and death rates rise with population density
what type of feedback are density dependent birth and death rates?
density dependent are negative feedback, population gets smaller when it gets really big
what do intrinsic factors play a role in?
in density-dependent birth and death rates, along with many other factors such as resources, disease, predation
what are intrinsic factors?
intrinsic factors are physiological factors that can regulate population size
examples of intrinsic factors?
in mice, overcrowded environment can cause hormonal changes and aggressiveness that increases mortality
in elephants, stress messes with hormones and slows reproduction
what is the trade off between survival and parental care?
normal amount of offspring are likely to get good care and survive (but may die of infection or predation), too many offspring can cause parents to get worn out and offspring may die
what are two ways to maintain population stability in humans?
zero population growth = high birth rate & high death rate or low birth rate & low death rate
what is the demographical transition?
going from high birth rate high death rate to low birth rate low death rate
what is demographic transition associated with in terms of women?
increasing health care and education may lower birth rates for women
what is age structure?
the relative number of individuals at each age
