Population Ecology and Dynamics

Comprehensive vocabulary flashcards covering human demography, population characteristics, population growth models, ecological sampling techniques, species interactions, and ecosystem energy flow.

Renewable resources

Resources that can be replaced naturally, such as solar and wind energy.

Non-renewable resources

Finite resources that take extremely long periods to replace, such as coal, oil, and natural gas.

Carrying capacity

The maximum population size that the environment can sustain indefinitely, given the available food, water, habitat, and other needed resources.

Garrett Hardin

An American ecologist who discussed population limits and resource use, asserting that Earth's resources are finite and that unlimited population growth cannot continue indefinitely.

Thomas Robert Malthus

Author who published an essay on the Principle of Population, theorizing that human populations have the potential to grow exponentially while food production tends to increase more slowly.

Voluntary checks

Malthusian checks on population growth that include birth control, abstinence, and delayed marriage.

Involuntary checks

Malthusian checks on population growth that include famine, disease, and war.

Ecological footprint

A measurement of the biologically productive land and sea area needed to produce the resources a person consumes and absorb or treat the waste they generate.

Global hectares (gha)

The unit of measurement for ecological footprints, representing $1\,\text{hectare}$ of biologically productive area with average global productivity.

Birth rate

The number of live births per $1000\,\text{people}$ per year.

Death rate

The number of deaths per $1000\,\text{people}$ per year.

Immigration

People moving into a country.

Emigration

People moving out of a country.

Demographic Transition Model (DTM)

A model that explains how birth rates, death rates, and population growth change as a society develops through distinct stages.

Replacement-level fertility

The average number of children per woman needed to replace a population from one generation to the next, which is $2.1\,\text{children/woman}$ for developed countries.

Tragedy of the Commons

A concept identified by Garrett Hardin in 1968 occurring when people overuse a shared resource for their own benefit, eventually damaging it for everyone.

Population

A group of individual organisms of the same species that live together in the same geographic area.

Population density

The number of individuals in a given area, describing how many individuals occupy a specific amount of space.

Crude density

The total number of individuals divided by the total area ($\text{Crude density} = \frac{\text{total \# of individuals}}{\text{total area}}$).

Ecological density

The number of individuals per unit of suitable habitat ($\text{Ecological density} = \frac{\text{individuals}}{\text{area of suitable habitat}}$).

Population dispersion

How individuals of a population are distributed throughout the area they occupy.

Clumped dispersion

A distribution pattern in which individuals group together in particular areas, as seen in grass, flocking birds, or fish.

Uniform dispersion

A distribution pattern where individuals are spaced relatively equally across an area, such as nesting seagulls or sea lions on a beach.

Random dispersion

A distribution pattern where individuals are scattered randomly throughout an area, such as rainforest trees or microscopic marine plankton.

Quadrant sampling

A sampling method involving counting individuals within selected sample areas called quadrants (defined areas within a larger habitat) to estimate total population.

Mark-and-recapture sampling

A method of capturing, marking, and releasing organisms, then capturing another sample to determine how many marked individuals are recaptured using the formula $N \approx \frac{M \times C}{R}$.

Type I survivorship curve

A survivorship pattern where mortality is generally low during early and middle life and increases at older ages, typical of species producing relatively few offspring like humans and whales.

Type II survivorship curve

A survivorship pattern with a relatively consistent chance of dying throughout life, meaning young and old individuals have equal chances of surviving (e.g., insects).

Type III survivorship curve

A survivorship pattern where many individuals die early, but survivors of early stages have higher chances to live longer, compensated by producing many offspring (e.g., sea turtles, small fish).

Fecundity

The number of offspring an individual can produce in its lifetime.

Age structure

The distribution of individuals among different age groups within a population.

Habitat

An area with particular environmental characteristics defined by combinations of abiotic and biotic factors.

Abiotic factors

Physical, non-living components of the environment.

Biotic factors

Living components of the environment.

Natality

Births in a population, which increase the population size.

Mortality

Deaths in a population, which decrease the population size.

Closed population

A population whose size changes only through births and deaths because immigration and emigration do not affect it.

Open population

A population whose size can change through all four factors: natality, mortality, immigration, and emigration.

Net population change ($\Delta N$)

The overall change in population size after considering births, deaths, immigration, and emigration: $\Delta N = (b + i) - (d + e)$.

Population dynamics

The change in population size over time.

Population ecology

The study of how populations change over time in their relation to their environment and other species.

Geometric Growth Model

A model applying to populations with discrete breeding seasons that uses a constant multiplier ($\lambda = \frac{N(t+1)}{N(t)}$) to change population size each time step, resulting in exponential growth.

Exponential Growth Model

A model describing continuous population growth with overlapping generations, given by the differential equation $\frac{dN}{dt} = rN$.

Biotic potential

The maximum population growth rate that could occur under ideal conditions for an organism ($r\,\text{at max}$).

Logistic Growth Model

A model accounting for habitat resources where growth slows as the population approaches carrying capacity ($K$), producing a sigmoid curve.

Lag phase

The initial phase of logistic growth characterized by a slow, relatively constant, arithmetic increase.

Log phase

The phase of rapid growth in a logistic model where the population accelerates from slow growth to an exponential pattern.

Stationary phase

The final stage of logistic growth where the curve flattens into a plateau with an overall growth rate of $0$.

Dynamic population equilibrium

A state indicated by natural populations fluctuating around carrying capacity ($K$).

Density-dependent factors

Internal factors whose effects on population size change with density, such as predation, resource availability, disease, stress, and aggression.

Density-independent factors

External, mostly abiotic factors whose effects do not depend on population density, such as weather, fires, drought, volcanic eruptions, and pollution.

Population cycles

A pattern of repeated increases and decreases in population size over a regular period, often caused by multi-factor interactions like predator-prey dynamics.

Community

Populations of different species interacting in the same area.

Ecosystem

Communities interacting with one another and with abiotic processes.

Niche

How an organism uses its habitat and resources, including its entire way of life.

Interspecific competition

Competition between members of different species for the same limited resources.

Intraspecific competition

Competition between members of the same species for the same limited resources.

Interference competition

Direct interactions where organisms prevent one another from accessing a resource, such as lions fighting over a kill.

Exploitative competition

Indirect competition where organisms consume or use the same limited resource, such as species sharing a food supply.

Competitive exclusion

The outcome where two species compete for the same limiting resource in the same niche, causing the less successful competitor to decline or disappear.

Fundamental niche

The full range of conditions and resources a species could theoretically use in the absence of limiting interactions like competition.

Realized niche

The conditions and resources a species actually uses in nature when factoring in competition and other limiting interactions.

Resource partitioning

The division of resources into different subsets by similar species, reducing direct competition and allowing coexistence in the same habitat.

Predation

An ecological interaction where a predator feeds on prey, creating selection pressure for prey to evolve defensive adaptations.

Morphological defences

Physical structures that make organisms harder to catch or consume, such as porcupine quills or turtle shells.

Chemical defences

Chemicals that make organisms poisonous or unpalatable to deter predators, sometimes sequestered from plants eaten.

Protective colouration

Colouring or patterns that help organisms avoid predators, divided into camouflage (blending into surroundings) and warning colouration (signaling toxicity).

Symbiosis

A close relationship between two different species in which at least one species benefits.

Mutualism

A symbiotic relationship in which both species benefit, such as bees and flowers.

Commensalism

A symbiotic relationship in which one species benefits while the other is unaffected, such as barnacles and whales.

Parasitism

A symbiotic relationship in which one organism benefits while the other is harmed, such as roundworms in a vertebrate host.

Trophic levels

An organism's feeding position in the transfer of energy through an ecosystem.

Food chain

A linear feeding relationship showing how energy moves from one organism to another.

Food web

A complex network of interconnected food chains within an ecological community.