SBI4U - Population Dynamics

Population density

The number of individuals of one species per unit area

Population density formula

Total organisms / total area

Mark-Recapture Sampling formula

Total marked (M) / total pop. (N) = recaptures (m) / size of 2nd sample (n). Used when physical counting is impossible

Carrying capacity

The maximum population that an ecosystem can sustain (K)

Fedundity

The potential number of offspring a species can produce in its lifetime

Survivorship

The pattern exhibited by the average age of death within a species

Survivorship curves

Type I - humans, Type II - hawks, Type III - frogs

Density dependent factors

Limit population growth, and are intensified with increased populations

Intraspecific Competition

When individuals of the same species compete for the same resources

Predation

Density dependent factor, prey that are more abundant become easy targets

Disease

Density dependent factor, in large populations there is a greater chance of occurrence and spread of disease

Minimum viable population size

The smallest number of individuals that ensures a population can persist

Density independent factors

Limit population growth, regardless of population size, usually from human intervention or extreme changes

Limiting factor

The resource required by an organism that is in shortest supply

Ecosystem

A community of organisms and their environment, including all biotic and abiotic factors

Species

Organisms that are similar in appearance and are able to interbreed

Population

All members of a single species living in a region

Community

A collection of populations located in the same geographic location

Biome

A large community of organisms that occupy a distinct region

Biosphere

The global sum of all ecosystems

Habitat

The natural home of a plant or animal

Ecological Niche

The role an organism plays in its environment

Range

The distribution of the geographical area in which a species may be found

Producer

An organism that generates its own food from sunlight

Quadrat

Used to study stationary species, population is physically counted inside quadrat

Clumped dispersion

Organism are densely grouped, result of clumped resources, and social behaviour (packs or herds)

Uniform dispersion

Individuals evenly distributed, results from competition, species set up territories

Random dispersion

Individuals randomly dispersed, results when organisms are minimally influenced by interactions

Intrinsic Growth Rate

Rate determined from the difference between births and deaths (r)

Logistic Growth

When growth is restricted by resources, and the population stops growing at the carrying capacity

Geometric Growth

In species where birth rates occur at set intervals (mating seasons), population spikes at certain times of year

Interspecific Competiton

Occurs between two different species, restricts population growth

Interference Competition

When two species compete for a resource aggressively, preventing the other from accessing a resource, ex birds of prey

Resource Partitioning

Resources are divided by organisms occupying two non-overlapping ecological niches, reduces competition

Fundamental niche

Under ideal conditions, making optimal use of resources to maximize health and growth rate

Realized niche

Occupy a portion of the fundamental niche, due to interspecific competition

Coevolution

When the evolution of predators directly effects the evolution of prey, and vice versa

Chemical defence

Prey develop chemical means to make them poisonous or unpleasant to predators, ex skunk, monarch

Morphological defence

Body structures which may be harmful to predators who attack, ex porcupine

Camouflage

Coloration of prey to avoid detection by blending into surroundings

Warning coloration

Prey with chemical defended, exhibit bright coloration to warn predators, ex frogs

Symbiosis

When two different species live in close, usually physical, contact

Mutualism

Type of symbiosis, both organisms benefit, ex oxpecker birds on backs of grazing animals

Commensalism

Symbiosis, one organism is benefited, other is unaffected, ex clown fish and sea anemone

Parasitism

Symbiosis, one animal benefits, other is harmed, ex ticks

Predator/Prey cycles

Sinusoid, predator lags behind, cycle at regular intervals, both populations affected

Defence mechanism

Prey develop to avoid predators, many different types

Invasive species

Non-native species, out compete native species for resources and end up taking over, ex zebra mussels

Lag phase

Beginning of logistic growth, growth rate is slow

Log phase

Middle of logistic growth, maximum growth rate

Stationary stage

End of logistic growth, carrying capacity is reached