Environmental Science: Population and Survivorship

(Population) Distribution

Characteristic of population concerning how individuals are spaced out in a population; random, uniform, or clumped; influences measure of density

Survivorship

Characteristic of population concerning mortality scale; 3 types

Sex ratio

Characteristic of population concerning the ratio of males to females; close to 50:50 in most species

Population size

Characteristic of population that includes the number of individuals in a population

population density

Characteristic of population that measures the number of individuals per unit area

Population

Individuals of the same species, living in the same place at the same time

Quadrat sampling

Method of measuring a population's size by measuring the population in a certain area or quadrant; used for sessile species

Capture-mark-recapture

Method of measuring population size in which the organism is captured and marked, usually with a plastic band or number, and then released; uses the Lincoln-Peterson Index to calculate estimation

Sessile

Slow moving or non-mobile organism whose population size can be estimated using the quadrat sampling technique

Type I (Survivorship)

Survivorship curve in which organisms had parental care; not much death during adolescence but population drops around middle age; ex. humans, gorillas, elephants

Type II (survivorship)

Survivorship curve in which parental care was present but not constant (parents leave children alone to find food, allowing predators to attack); constant slops/state of mortality; ex. birds

Type III (survivorship)

Survivorship curve in which there is no parental care; death usually occurs in adolescence with death rates slowing in middle/old age; ex. fish, turtles, frogs

Uniform (distribution)

Type of population distribution in which organisms are dispersed in a sort of pattern, usually because of social behavior

Clumped (distribution)

Type of population distribution in which organisms are in groups for protection purposes

Random (distribution)

Type of population distribution in which organisms are simply scattered in no specific way; happens in trees due to nutrient levels in soil

population ecology

the branch of biology that deals with the number of individuals of a particular species found in an area and how and why those numbers increase or decrease over time