APES CH 6 VOCAB

Population- the individuals that belong to the same species and live in a given area at a particular time

Community- all of the populations of organisms within a given area

Population ecology- the study of factors that cause populations to increase or decrease

Population density- the number of individuals per unit area at a given time

Population distribution- a description of how individuals are distributed with respect to one another

Sex ratio- the ratio of males to females in a population

Age structure- a description of how many individuals fit into particular age categories in a population

Limiting resource- a resource that a population cannot live without and that occurs in quantities lower than the population would require to increase in size

Density-dependent factor- a factor that influences an individual’s probability of survival and reproduction in a manner that depends on the size of the population

Carrying capacity (K)- the limit of how many individuals in a population the environment can sustain

Density-independent factor- a factor that has the same effect on an individual’s probability of survival and the amount of reproduction at any population size

Population size (N)- the total number of individuals within a designed area at a given time

Population growth models- mathematical equations that can be used to predict population size at any moment in time

Population growth rate- the number of offspring an individual can produce in a given time period, minus the deaths of the individual or its offspring during the same period

Intrinsic growth rate (r)- the maximum potential for growth of a population under ideal conditions with unlimited resources

Exponential growth model- (N_t=N₀e^rt)a growth model that estimates a population’s future size (N_t) after a period of time (t), based on (r) and the number of reproducing individuals in the population (N₀)

J-shaped curve- the curve of the exponential growth model when graphed

Logistic growth model- a growth model that describes a population whose growth is initially exponential, but slows as the population approaches the carrying capacity of the environment

S-shaped curve- the shape of the logistic growth model when graphed

Overshoot- when a population becomes larger than the environment’s carry capacity

Die-off- a rapid decline in a population due to death

K-selected species- a species with a low intrinsic growth rate that causes the population to increase slowly until it reaches carrying capacity

Survivorship curve- a graph that represents the distinct patterns of species survival as a function of age

Type 1 survivorship curve- a pattern of survival over time in which there is high survival throughout most of the life span, but then individuals start to die in large numbers as they approach old age

Type II survivorship curve- a pattern of survival over time in which there is a relatively constant decline in survivorship throughout most of the life span

Type III survivorship curve- a pattern of survival over time in which there is low survivorship early in life with few individuals reaching adulthood

Corridor- strips of natural habitat that connect populations

Metapopulation- a group of spatially distinct populations that are connected by occasional movements of individuals between them

Inbreeding depression- when individuals with similar genotypes-typically relatives-breed with each other and produce offspring that have an impaired ability to survive and reproduce 

Community ecology- the study of interactions between species

Symbiotic relationship- the relationship between two species that live in close association with each other

Competition- the struggle of individuals to obtain a shared limiting resource

Resource partitioning- when 2 species divide a resource based on differences in their behaviour morphology

Competitive exclusion principle- the principle stating that 2 species competing for the same limiting resource cannot coexist

Predation- an interaction in which one animal typically kills and consumes another animal

Parasitoid- a specialized type of predator that lays eggs inside other organisms (hosts)

Parasitism- an interaction in which one organism lives on or in another organism

Pathogen- a parasite that causes disease in its host

Herbivory- an interaction in which an animal consumes a producer

Mutualism- an interaction between 2 species that increases the chances of survival or reproduction for both species

Commensalism- a relationship between species in which one species benefits and the other species is neither harmed nor helped

Keystone species- a species that is not very abundant but has large effects on an ecological community

Ecological succession- the predictable replacement of one group of species by another group of species over time

Primary succession- ecological succession occurring on surfaces that are initially devoid of soil

Secondary succession- the succession of plant life that occurs in areas that have been disturbed but have not lost their soil

Pioneer species- a species that can colonize new areas rapidly and grow well in full sunshine

Climax community- historically described as the final stage of succession

Theory of island biogeography- a theory that demonstrates the duel importance of habitat size and distance in determining species richness