Ecology: Population Distribution, Growth, Regulation, Predation, and Parasitism

A set of vocabulary flashcards reviewing ecological principles of population distribution, abundance estimation, population growth, regulation, predation, and parasitism.

Population

A group of individuals of the same species that live in a particular area and interact with one another through processes such as sexual reproduction and competition.

Distribution

The geographic area where individuals of a given species occur.

Abundance

The number of individuals of a species present in a given area, commonly reported as total population size or density.

Ramet

A physiologically distinct individual produced through asexual or clonal propagation.

Genet

A single genetic individual originating from a single fertilisation event, which may consist of a single plant or an entire clone of ramets.

Line Transect

A distance sampling method where an observer travels along a fixed path, counting individuals and recording their perpendicular distance from the line to estimate abundance.

Mark–Recapture Method

A technique for estimating total population size ($N$) in mobile organisms by capturing and marking a sample ($M$), releasing them, and determining the ratio of marked ($R$) to total captured individuals ($C$) in a second sample using $N = \frac{M \times C}{R}$.

Ecological Niche

The full suite of abiotic and biotic conditions that an organism requires to grow, survive, and reproduce.

Niche Model

A predictive model that estimates a species' geographical distribution based on the environmental conditions present in locations where the species is currently known to occur.

Dispersion

The spatial arrangement of individuals within a population across a geographic area, commonly exhibiting regular, random, or clumped patterns.

Endemic Species

A species that occurs naturally in only one particular, restricted geographic region and nowhere else.

Metapopulation

A set of spatially isolated populations of the same species that are linked to one another by dispersal among suitable habitat patches.

Levins Metapopulation Model

A mathematical formulation ($\frac{dp}{dt} = cp(1 - p) - ep$) describing patch occupancy dynamics, establishing that a metapopulation persists only when the ratio of extinction rate to colonization rate ($\frac{e}{c}$) is less than $1$.

Population Outbreak

An extremely rapid and explosive increase in the density of a population over an unusually short period of time.

Population Cycles

Regular, repeating fluctuations between periods of high and low population abundance occurring at characteristic time intervals.

Delayed Density Dependence

A delay in the effect of population density on vital rates, causing growth at time $t$ to be regulated by population sizes present at a previous point in time ($\tau$), often leading to fluctuations or cycles.

Effective Population Size

The number of breeding individuals in a population that actively contribute offspring to the subsequent generation.

Extinction Vortex

A reinforcing downward cycle in small populations where inbreeding, genetic drift, and demographic fluctuations cause progressive reductions in size until local extinction occurs.

Inbreeding

Mating between genetically related individuals that elevates homozygosity and increases the expression of harmful recessive alleles.

Environmental Stochasticity

Unpredictable and random temporal variation in environmental conditions that affects birth and death rates across an entire population.

Geometric Growth

Population growth occurring when individuals reproduce in synchrony at discrete intervals, described mathematically by $N_{t+1} = \lambda N_t$ or $N_t = \lambda^t N_0$.

Exponential Growth

Continuous population growth over time under conditions of non-limiting resources, expressed by $\frac{dN}{dt} = rN$ and resulting in a J-shaped curve.

Density-Independent Factor

An environmental force, such as weather, temperature, or catastrophe, that influences per capita rates of birth, death, or dispersal independently of population density.

Density-Dependent Factor

A biotic or environmental factor whose per capita effects on birth, death, or dispersal rates change systematically as population density increases or decreases.

Carrying Capacity ($K$)

The maximum population size of a species that can be sustained indefinitely by the resources available in a particular environment.

Logistic Growth

A model of population growth ($\frac{dN}{dt} = rN \left(1 - \frac{N}{K}\right)$) in which population increase is initially rapid, slows as resources deplete, and approaches zero as density nears carrying capacity.

Life Table

A structured demographic summary detailing how survival, mortality, and reproductive rates vary by age, size, or developmental stage within a population.

Age Structure

The proportional distribution of individuals among different age classes within a population at a specific point in time.

Survivorship Curve

A plot showing the number or proportion of individuals from an initial cohort that survive to reach successive chronological ages.

Type I Survivorship Curve

A survival pattern wherein high survivorship is maintained throughout juvenile and adult life, followed by a sharp increase in mortality among older individuals.

Type II Survivorship Curve

A survival pattern in which individuals experience a constant per capita risk of mortality at all age stages throughout their lifespan.

Type III Survivorship Curve

A survival pattern marked by extremely high mortality rates early in life, with substantially lower and stable mortality rates for the few individuals reaching maturity.

Predation

A trophic interaction wherein individuals of one species consume and directly harm individuals of another species.

Carnivory

A form of predation in which both the predator and its prey are animals.

Herbivory

A trophic interaction wherein an animal consumes tissues of plants or algae, typically without causing immediate mortality to the autotrophic prey.

Crypsis

A morphological or behavioral antipredator adaptation in which prey are camouflaged or visually resemble their background to evade detection.

Mimicry

An evolutionary defense mechanism in which one organism evolves a resemblance to another toxic, dangerous, or unpalatable species to deceive predators.

Aposematic Coloration

Conspicuous warning color patterns displayed by prey to deter predators by signaling that they contain toxins, venoms, or distasteful chemicals.

Masting

The synchronized, episodic production of large seed crops across entire plant populations to satiate seed predators and increase seed survival.

Plant Compensation

A physiological tolerance response where herbivore damage or removal of plant tissue stimulates compensatory vegetative growth, branch proliferation, or increased reproduction.

Prey Zero-Growth Isocline

The specific predator abundance ($P = \frac{r}{a}$) in the Lotka–Volterra model at which the prey population growth rate is zero ($\frac{dN}{dt} = 0$).

Predator Zero-Growth Isocline

The specific prey abundance ($N = \frac{m}{ba}$) in the Lotka–Volterra model at which the predator population growth rate is zero ($\frac{dP}{dt} = 0$).

Symbiont

An organism that lives in intimate, persistent physical association on or within the body of another organism.

Parasite

An organism that lives symbiotically on or inside a host, consuming its tissues or bodily fluids and reducing host fitness without killing it immediately.

Pathogen

A parasite or microparasite that induces distinct pathology or disease symptoms in its host.

Ectoparasite

A parasitic organism that lives, feeds, and resides entirely on the exterior surface of its host's body.

Endoparasite

A parasitic organism that inhabits the interior tissues, organ cavities, or cells of its host.

Zoonotic Disease

An infectious disease caused by pathogens naturally transmitted between non-human animals and humans.

Disease Reservoir

A host species or population in which a pathogen naturally persists and replicates over long periods, acting as a continuing source of transmission.

Disease Vector

An agent, commonly an arthropod such as a tick, mosquito, or sandfly, that acquires and transmits a pathogen from one host to another.

Phytoalexins

Antimicrobial and antifungal chemical compounds synthesized by plant cells at the site of tissue injury or microparasite attack to restrict pathogen spread.