Midterm 1 Week 4 Flashcards
population
a group of individuals of the same species in a given area that have the potential to interbreed and interact.
metapopulation
group of geographically isolated populations linked together by dispersal
population size
number of individuals within a population
population density
number of individuals per unit area
population dynamics
spatial and temporal patterns and processes of population change in size, density, and/or age structure
3 spacial dispersion patterns: clumped, regular, random
Clumped: presence of one individual at any point increases probability of others being near that point
Regular: presence of one individual at any point reduces probability of others being near that point thus individuals are evenly spaced in the area occupied by the population
Random: there is an equal probability of an individual occupying any point in space
sampling: full census, quadrat, transect, mark-recapture methods
Full census: used when organisms are large, populations are small, and it is possible to identify each individual.
Quadrat: measured areas.
Transect: linear lines drawn across the population’s range.
Mark-recapture method: involves capture, marking, and releasing some individuals, then later capturing another sample of individuals. (# marked in 2nd sample/ total caught in second sample) = (# marked in 1st sample/size of whole population)
open population
population “open” to individuals immigrating into, and emigrating out of, the populationNt+1= Nt+ (B –D) + (I–E)
closed population
population “closed” to immigration and emigration; only births and deaths in the population affect the growth of closed populations
Nt+1=Nt+(B-D)
dispersal
movement of individuals into (immigration) or out of (emigration) an existing population
migration
movement of a whole population, usually in response to seasonal variation in resources
immigration
movement in
emigration
movement out
population growth
Quantifying the size and dispersion pattern of a population is useful but not sufficient to explain how, when, and why populations change in size over time.
Nt+1 = Nt + (B-D)+(I-E)
finite rate of increase
population’s per-individual growth rate across any two time periods. finite rate of increase = Nt+1/Nt
per capita birth rate
no. of births/individual/unit time
B = bN
per capita death rate
no. deaths/individual/unit time
D = dN
per capita growth rate
r = b - d
population growth rate
rN = dN/dt
describes growth rate of a population increasing exponentially
exponential population growth and curve
the number of new individuals added (born) per unit of time accelerates with time even though r, the per capita rate of increase, remains constant.
All populations have the potential for exponential growth when resources (food, space, etc.) are plentiful.
per-capita growth rate is constant; population growth is density independent
logistic population growth and curve
per-capita growth rate varies with population density; population growth is density dependent. (S-shaped curve)
carrying capacity (K)
maximum population size that can be supported by available resources or physical space
density dependent population growth
are processes, such as reproduction, mortality, population growth, that are affected by the density of organisms present at each time period
if density-dependent processes act, a population will grow more slowly during later time intervals when population size (N) is high than it did during earlier time intervals when N is low.
density independent population growth
are processes, such as extreme cold or a hurricane, that may kill a large number of individuals in a population independent of the population’s density
life table
accounting tools that keep track of demographic events* in populations and can be used to determine the rate at which they occur
summarize how survival and reproductive rates vary with the age, size, or sex of individuals in the population
cohort life table
life table that keeps track of a cohort (group of individuals born within the same time frame) from the larger population to estimate growth rate
age-specific survivorship
lx = age-specific survivorship = proportion of the original cohort of individuals that survive to age x
age-specific fecundity
mx = age-specific fecundity = average number of offspring produced by an individual of age x
net reproductive rate
combine information on age-specific survivorship (lx) and age-specific fecundity (mx) .
mean number of offspring produced per individual in the cohort, adjusted for age and survival
R > 1: # offspring increase
R < 1: # offspring decrease
R = 1: # offspring constant
survivorship curves
summarize the pattern of individuals surviving through each life stage in a population
there are 3 general shapes
correlated with general life history patterns
Type I Survivorship
high survivorship through adulthood; low reproductive rate but lots of parental care thus risk of death at early life stages is reduced; humans, elephants, other large mammals
Type II Survivorship
constant risk of mortality at all ages; many birds, fish, plants
Type III Survivorship
low survivorship early in life, higher once maturity is reached; produce many offspring; little or no parental care; most insects, marine invertebrates, annual plants
life history
lifetime pattern of growth, reproduction, and survival for an average individual.
life history strategy
the way in which a species allocates resources to growth, reproduction, and survival based on genetic and environmental factors.
r-strategists
display traits that make a species successful when population densities are far from K and population growth is driven by “r”. Examples: annual weeds, house flies, rabbits
k-strategists
display traits that make a species successful when population densities are near K. Examples: oak trees, bison
age structure
and proportion of individuals in a population
