Population Ecology Flashcards
Population
- a group of individuals of the same species that live in the same area at the same time
- and potentially interact with each other
- defining borders of a population can be difficult
Metapopulation
a population of populations connected by migration (gene flow)
Range of species
- different scales
- populations are displayed in a patchy way depending on the suitability of the environment
- as you zoom in there are more and more populations
Population Density
the number of individuals per unit area
Population Dispersion
- how individuals are distributed relative to one another
- 3 main types: Random, Clumped, and Uniform
Random Dispersion
- an individual has an equal probability of occurring anywhere in an area
- e.g. a field of dandelions have wind dispersion
Clumped Dispersion
- individuals are closer than expected by chance
- if natural selection has favored being close to another individual
e. g. schools of fish reduce the chance of predators eating an individual
Uniform Dispersion
- relatively equal spacing among individuals
- maximize space
- if natural selection has favored being farthest away from each other
- e.g. plants in the desert are uniformly spaced because their roots are competing for water in the soil
3 Main Ways to Calculate the Size of A Population
- Count all individuals in the population
- Sub-sample and extrapolate
- Mark-recapture
Counting all individuals int he population
-usually not possible, unless there is a small population such as the Northern Spotted Owl
Sub-sample and extrapolate
- estimate of population size
- e.g. quadrant and transect sampling
potential difficulties:
- over what area do you extrapolate
- heterogeneous habitat (not every sample is the same and leads to inaccurate estimate)
- movement of individuals
Mark-Recapture
mark: catch some individuals and mark them
recapture: return later and catch some individuals and tally number marked and unmarked
M/N = m/n M- number marked m- number marked in recapture N- estimated population size n- total in recapture
assumptions:
- individuals not moving in/out of study area
- individuals size between captures
- no catch bias
- no fitness difference between marked and unmarked
Demography
- study of vital statistic of populations
- birth and immigration rates (+)
- death and immigration rates (-)
- the values of vital statistics depend on the traits of the focal organisms
- these factors are part of what determines the population size
Life table
- summarizes age-specific demographic stats
- data gathered for a cohort
Cohort
- group of the same age that can be followed through time
- e.g. group of lizards born the same summer
Survivorship
-the average proportion of a cohort that survives to a particular age class
Fecundity
- the number of females produced by each female
- average births/year/original female
Net-reproductive Rate
- growth rate of a population per generation
- average number of female offspring that each female produces over her lifetime
Fertility
-average number of offspring (male + female) that a female produces during lifetime