Grade 12 biology - Natural population Dynamics

population ecology

a sub-field of ecology that focuses on the dynamics of populations and how populations interact with their environment

Geographic range

the overall spatial boundaries within which a population lives

Habitat

the place where an organism normally lives

Population size (N_t)

the number of individuals of a specific species that occupies a given area or volume at a given time

population density (D)

the number of individuals of the same species that occurs per unit area or volume

crude density

population density measured in terms of the number of organisms of the same species within the total area of the entire habitat

Ecological density

population density measured in terms of the number of individuals of the same species per unit area or volume that is actually used by the individuals

Dispersion

The pattern of distribution in which a population exists; may be clumped, random, or uniform

quadrat

a sampling frame that is used for estimating population size; the frame can be real or virtual

Mark-recapture method

A sampling technique for estimating population size and density by comparing the proportion of marked and unmarked animals that are captured in a given area; sometimes called the capture-recapture method

Demography

the study of the growth rate, age structure, and other characteristic of populations

Natality

the birth rate in a population

Morality

the death rate in a population

immigration

the movement of individuals into a population

emigration

the movement of individuals out of a population

Life table

A chart that summarizes the demographic characteristics of a population

cohort

a group of individuals of similar ages

Age-specific mortality

the proportion of individuals that were alive at the start of an age interval but died during the age interval

Age-specific survivorship

the proportion of individuals that were alive at the start of an age interval and survived until the start of the next age interval

Survivorship curve

a graphic display of the rate of survival of individuals over the lifespan of a species

Fecundity

the potential for a species to produce offspring in a lifetime

Generation time

the average time between the birth of an organisms and the birth of its offspring

Sex ratio

the relative proportion of males and females in a population

Population dynamics

the change in a population over time

Exponential model of population growth

a pattern of population growth in which organisms reproduce continuously at a constant rate

per capita growth rate

the difference between the per capita birth rate and the per capita death rate of population

Zero population growth

a situation in which the death rate and the birth rate are in equilibrium

Carrying capacity (K)

the number of individuals in a population that the environmental resources can support

Logistic model of population growth

a model that describes limited population growth, often due to limited resources or predation

Sigmoid curve (Logistic)

an S-shaped curve, typical of population growth that starts slow, accelerates or grows rapidly, and then levels out over time

Limiting factor

A factor that limits the growth of a population

Density-dependent factor

A factor that is influenced by population density, having a greater impact as the population density increases

Density-independent factor

A factor that influences population regulation regardless of population density

Competition

An interaction in which both competing populations lose access to some resources

Interspecific competition

Competition between members of different species

Intraspecific competition

Competition between members of the same population for resources

Predation

the interaction between predator and prey

Allee effect

A density-dependent phenomenon that occurs when a population cannot survive or fails to reproduce enough to offset mortality once the population density is too low

minimum viable population size

the smallest population size that is likely to survive both predictable and unpredictable environmental variation; note that it is only a prediction

Coevolution

a process in which one species evolves in response to the evolution of another species

Herbivory

the interaction between herbivorous animals and the plants that they eat

Mutualism

An interaction in which both partners benefit

Parasitism

An interaction in which one species benefits and the other is harmed

Commensalism

An interaction in which one species benefits and the other is unaffected

mimicry

A form of defence in which one species evolves an appearance that resembles the appearance of another species

interference competition

competition in which all the individuals have equal access to resource; the fitness of some individuals is reduced by the presence of others

Exploitative competition

competition in which all the individuals have equal access to resources; some have superior ability to gather resources

Fundamental niche

the range of conditions and resources that a population can possibly tolerate and use

Realized niche

the range of conditions and resources that a population actually uses in nature

resource partitioning

a situation in which several species that live in the same place use different resources or use the same resources in different ways