Bio Ch 12 - Population distributions

Geographic range

a measure of the total area covered by a population

Spatial structure

the pattern of density and spacing of individuals in a population

Fundamental niche

the range of abiotic conditions under which species can persist

Realized niche

the range of abiotic and biotic conditions under which a species can persist

Endemic species

species living in a single, often isolated location

Cosmopolitan species

species with very large geographic ranges that can span several continents

Ecological niche modeling

the process of determining the suitable habitat conditions for a species

Ecological envelope

the predicted range of ecological conditions that are suitable for a species

Abundance

the total number of individuals in a population that exist within a defined area

Density

in a population, the number of individuals in a unit of area or volume

for most species, the largest density of individuals occurs near the center of a population’s geographic range

Dispersion

the spacing of individuals with respect to one another within the geographic range of a population

Dispersal

the movement of individuals from one area to another

different from migration, it is not seasonal movement. instead, it allows species to colonize areas outside of their geographic ranges

Clustered dispersion

a pattern of population dispersion in which individuals are aggregated in discrete groups

ex. fungi grow in clusters anywhere where there is a rotting stump

Evenly spaced dispersion

a pattern of dispersion of a population in which each individual maintains a uniform distance between itself and its neighbors

Random dispersion

a pattern of dispersion in which the position of each individual is independent of the position of other individuals

Census

a count of every individual in a population

Survey

a count of a subset of the population

Area and volume-based surveys

surveys that define the boundaries of an area or volume and then count the individuals in that space

the size of the defined space is related to the abundance and density of population

average sample can be determined

Line-transect surveys

surveys that count the number of individuals observed as one moves along a line

Mark-recapture surveys

a method of population estimation where researchers capture and mark a subset of a population, return it to the environment, and then recapture a second sample of the population after some time

Lifetime dispersal distance

the average distance an individual moves from where it was born to where it reproduces

provides an estimate for how fast a population can increase its geographic range

Population abundance and density

populations with high abundance also have large geographic ranges

may be caused by resource availability; species are likely to cover the area that contains the resources they require

Body mass and population density

the density of a population is negatively correlated to the body size of the species

we can expect a plot of land to support fewer large individuals compared to small individuals

Dispersal limitation

the absence of a population from a suitable habitat because of barriers to dispersal

barriers often include large expanses of inhospitable habitat, and the barriers created by humans (roads, forest clearings)

most dispersed species do not establish viable populations

Habitat corridor

a strip of favorable habitat located between two large patches of habitat that facilitates dispersal

studies have been conducted that compare patches of habitats connected by habitat corridors to unconnected patches

connected patches experienced a higher number of recaptured organisms, greater pollination of plants and greater seed dispersal by birds

Ideal free distribution

as individuals move to a high-quality habitat, resources must be divided among more individuals (reduced per capita benefit)

because of this, an individual may benefit from moving to a lower-quality habitat

ideal free distribution is when individuals distribute themselves among different habitats in a way that allows them to have the same per capita benefit