Biology 30 - Unit 5 Booklet 1: Population and Community Dynamics (Terms)

Population

All the members of a species that occupy a particular area at the same time

Species

A group of organisms that has the potential to interbreed in nature to produce viable, fertile offspring

Evolution

The change in the frequency of genes in a population’s gene pool from one generation to the next

Gene Pool

The total of all genes in all the members of a population at one time; all alleles in a population

Hardy-Weinberg Principle/Equilibrium

A law used to quantify an unchanging gene pool stating that the frequencies of alleles in a population’s gene pool remain constant over generations if all other factors remain constant

Genetic Equilibrium

A state of stability in which allele and genotype frequencies in a population remain constant from one generation to the next, meaning there is no evolution occurring

p

Frequency of the dominant allele in the hardy-Weinberg equilibrium

q

Frequency of the recessive allele in the hardy-Weinberg equilibrium

p²

Frequency of the homozygous dominant genotype

2pq

Frequency of the heterozygous genotype

q²

Frequency of the homozygous recessive genotype

Micro-evolution

A change in the gene pool of a population over successive generations

Macro-evolution

A change in the phenotype of a population over successive generations as a result of selective pressures favouring a certain allele

Natural Selection

The phenomenon mainly reliant on abiotic factors in an environment that acts on the variations provided by mutations selecting more successful alleles

Gene Flow

Movement of alleles from one population to another through the movement of individuals or gametes

Sexual Selection

The selection of a trait that improves mating success of the individual due to those individuals having higher reproductive success

Sexual Dimorphism

A sexually selected trait resulting in striking physical or behavioural differences between males and females

Genetic Drift

Change in the gene pool of a population resulting from chance fluctuations

Chance Fluctuations/Events

An accidental event caused by chance that results in death or isolation and thus changes the gene pool of a population (ex. natural disasters)

Founder Effect

Genetic drift that results when a small number of individuals separate from their original population and thus become a new, separate population

Bottleneck Effect

A dramatic, often temporary reduction in population size that usually results in genetic drift

Population Density (D_p)

The number of individuals of the same species that occur per unit area (land) or volume (aquatic)

Natality

Number of births per unit of time

Immigration

Number of individuals that move into an existing population per unit of time

Mortality

Number of deaths per unit of time

Emigration

Number of individuals that move away from an existing population per unit of time

Exponential Growth

A population growth model characterized by rapid growth followed by rapid death corresponding with r-selected species that resembles a “J-curve”

Logistic Growth

A population growth model characterized by fluctuations around a carrying capacity corresponding with k-selected species that resembles an “S-curve”

Biotic Potential

The theoretical maximum growth rate of a species under ideal conditions affected by the time and level of ease in which a species can reproduce (ex. growth rate depending on number of offspring per birth, gestation time, reproductive age, etc.)

Environmental Resistance

Any limiting factor that restricts a population’s ability to reach its full biotic potential (ex. limited amounts of food, water, space, light; competition; abiotic factors such as weather)

Density-Dependent Factors

Factors affecting population change depending on a population’s density that influence a population only when a population is at a certain number

Density-Independent Factors

Factors affecting population change that influence every population regardless of their density

Intraspecific Competition

Competition within the same species (within a population) for resources in the environment (ex. competition for food per individual, space, sunlight, mates. etc.)

K-Selected Organisms

Organisms that have adapted to living in a population that is at or near carrying capacity (mammals, large organisms)

R-Selected Organisms

Organisms that have adapted to increase population size rapidly in order to prepare for rapid death

Interspecific Competition

Competition between species in the same community for resources in the environment (ex. competition for food sources, space, etc.)

Symbiosis

A close relationship between members of different species

Mutualism

Symbiosis in which both species benefit from the relationship

Commensalism

Symbiosis in which one species benefits from while the other is unaffected by the relationship

Parasitism

Symbiosis in which one species benefits from while the other species is farmed by the relationship

Succession

The sequence of identifiable ecological stages or communities occufring over time in progress from bare rock to climax community

Primary Succession

The initial colonization of a barren habitat by pioneer species, producing soil

Secondary Succession

Re-building of an area that once supported many organisms

Pioneer Species

Species that are commonly r-selected that are the first species to appear during succession

Climax Community

The final stage in ecological succession that is stable and self supporting in which more organic material is produced than used