Biology 30 - Chapter 20

population density (DP)

the number of individual organisms (N) in a given area (A) or volume (V); expressed as Dp = N/A or Dp = N/V

growth rate (gr)

change in population size (N) over a specific time frame (t); N is equivalent to the number of births plus immigration minus the number of deaths plus emigration; expressed as gr = N/t

per capita growth rate (cgr)

change in population size per individual over a given time frame; expressed as cgr = N/N or cgr = (Nfinal – N)/N

biotic potential (r)

highest possible per capita growth rate for a population, given unlimited resources and ideal living conditions

exponential growth pattern

pattern exhibited by a population which is increasing exponentially (i.e., doubles repeatedly); results in a J-shaped curve showing a brief lag phase, followed by a steep increase in the growth curve

logistic growth pattern

population increase that results in an S-shaped curve; growth is slow at first, steepens in an exponential pattern, and then levels off due to environmental resistance such as competition

carrying capacity (K)

theoretical maximum population size that the environment can sustain over an extended period of time; may change over time as the habitat changes

density-dependent factor

biotic factor that limits a habitat’s carrying capacity (e.g., parasites, disease); the impact increases with the density of the population; compare density-independent factor

environmental resistance

combined effects of various interacting factors that limit population growth; prevents a population from growing at its biotic potential and determines the carrying capacity of the habitat

density-independent factor

abiotic factor that limits a habitat’s carrying capacity (e.g., fi re, flood); the impact is not affected by the density of the population; compare density-dependent factor

r-selected strategy

a life strategy designed to take advantage of favourable conditions; characterized by a high reproductive rate with little or no attention given to offspring survival; organisms that exhibit this strategy include bacteria and species that reproduce close to their biotic potential (r); also known as r-selection

K-selected strategy

a life strategy designed to take advantage of stable environmental conditions; characterized by the production of a few offspring with much attention given to offspring survival; organisms that exhibit this strategy include mammals and species that live close to the carrying capacity (K) of their habitats, also known as K-selection

intraspecific competition

competition competition for limited resources among members of the same species; compare interspecific competition

interspecific competition

competition for limited resources among members of different species; compare intraspecific competition

Predator

organism that kills and consumes other organisms

Prey

organism that is killed and consumed by another organism

protective coloration

adaptation that helps individuals avoid predation; includes camouflage, mimicry, and using body colours as a warning signal

Symbiosis

direct or close relationship between individuals of different species that live together; usually involves an organism that lives or feeds in or on another organism (host); three forms are mutualism, commensalism, and parasitism

Mutualism

a type of symbiotic relationship in which both partners benefit from the relationship, or depend on it in order to survive

Commensalism

a type of symbiotic relationship in which one individual lives close to or on another and benefits, and the host neither benefits, nor is harmed

Parasitism

a type of symbiotic relationship in which an organism benefits by living on or in an organism of a different species that is harmed by the association

Succession

sequence of invasion and replacement of species in an ecosystem over tim

primary succession

the development of a new community in a previously barren area where there is no soil present, such as on a hardened lava bed, or on a bare rock mountaintop; compare secondary succession

pioneer community

first species to colonize a barren or disturbed habitat and initiate primary succession

climax community

the last or final stage of succession in an area; may remain relatively stable if there are no major environmental changes

ecological disturbance

event that changes the structure of a community, sometimes destroying all actively growing organisms

secondary succession

the regrowth of a previously existing community after an ecological disturbance, such as a forest fire, flood, or agricultural activity; differs from primary succession in the presence of soil, which is not usually destroyed in an ecological disturbance

Sustainability

concept of living in a way that meets our needs without compromising the health of future generations or of the planet

age pyramid

representation of the age structure of a population to show the proportion of individuals in the population in each age class; used by demographers to assess a population’s potential for growth