Ecology: Behaviour, Life Histories, Population Dynamics, and Disease

Vocabulary flashcards covering behavioural ecology, mating systems, life histories, population structure, growth models, and disease ecology from Lectures 11–18.

Behavioural Ecology

The study of interactions between organisms and their environment that are mediated by behaviour.

Behaviour

The internally coordinated responses (actions or interactions) of whole living organisms (individuals or groups) to internal and/or external stimuli (Levitis et al. 2009).

Adaptive Behaviour

A behaviour that increases the survival and/or reproductive success (fitness) of an organism, requiring at least a partial genetic basis so it can be selected across generations.

Foraging Gene (PKG)

A gene that produces protein kinase G (PKG) in honeybees; higher PKG expression causes older bees to forage outside the hive, whereas lower PKG expression causes younger bees to remain inside for brood care.

Fitness

The number of offspring contributed by an individual relative to the number of offspring produced by other members of the population.

Hamilton's Four Classes of Social Interaction

A matrix classifying social interactions based on fitness consequences: Cooperation (+ donor, + recipient), Altruism (- donor, + recipient), Selfishness (+ donor, - recipient), and Spite (- donor, - recipient).

Inclusive Fitness

The total fitness of an individual determined by its own survival and reproduction plus the survival and reproduction of its genetic relatives (Hamilton, 1964).

Kin Selection

An evolutionary mechanism in which individuals increase their inclusive fitness by aiding the survival and reproduction of relatives (kin).

Hamilton's Rule

The rule stating that an altruistic trait is favoured by natural selection when $R_g \times B > C$, where $R_g$ is genetic relatedness, $B$ is reproductive benefit to the recipient, and $C$ is reproductive cost to the donor.

Coefficient of Relationship ($R_g$)

The probability that alleles at a given locus are identical by descent between two individuals in a population.

Eusociality

A social system characterized by: (1) individuals of more than one generation living together, (2) cooperative care of young, and (3) division of individuals into sterile/non-reproductive and reproductive castes.

Haplodiploidy

A sex-determination system in Hymenoptera where males develop from unfertilized haploid eggs and females develop from fertilized diploid eggs, making sisters related by $75\%$ ($0.75$) and more related to each other than to their brothers ($50\%$).

Altruism by Manipulation

A situation where a host displays seemingly altruistic behaviour because it has no mechanism to recognize or prevent being exploited by a parasite (e.g., an eastern phoebe feeding a brood-parasitic brown-headed cowbird).

Spite

A rare social behaviour that confers fitness disadvantages on both the donor performing the act and the recipient (e.g., chronically infected European badgers leaving kin and dispersing to infect non-kin).

Anisogamy

Sexual reproduction involving the fusion of two morphologically dissimilar gametes that differ in size and energy cost (large ova/eggs vs. small sperm/pollen).

Parts of a Flower

Reproductive and sterile structures of an angiosperm flower, including the stamen (male anther and filament), pistil (female stigma, style, and ovary), petals, and sepals.

Sequential Hermaphroditism

A life-history pattern where an individual changes sex over time, divided into protandry (male to female, e.g., clownfish) and protogyny (female to male, e.g., cleaner wrasse).

Social Monogamy vs. Genetic Monogamy

Social monogamy involves forming a pair bond and raising young together despite potential extra-pair copulations; genetic monogamy requires exclusive parental fidelity where all offspring are the pair's genetic descendants.

Polygyny

A mating system in which one male forms sexual relationships or mates with multiple females (e.g., harems in elephant seals, red-winged blackbirds).

Polyandry

A mating system in which one female mates with multiple males (e.g., jacanas, dunnocks exhibiting cloacal pecking to assure paternity).

Polygynandry

A mating system in which multiple males mate with multiple females within a shared social group (e.g., bonobos).

Intersexual Selection

Sexual selection driven by mate choice, where individuals of one sex select for ornamental traits (coloration, displays, acoustic songs) in the opposite sex.

Intrasexual Selection

Sexual selection driven by competition among individuals of the same sex for access to mates, favouring weapons, larger body size, and dominance displays.

Sexual Conflict

An evolutionary asymmetry in the costs and benefits of mating between sexes, prompting an intersexual arms race between male persistence and female resistance.

Life History

A description of the major characteristics of an organism from birth to death, encompassing patterns of growth, reproduction, and survival over its lifetime.

Allometry

The study of the relationship between organism body size and various biological traits or functions, including anatomy, physiology, and behaviour.

Principle of Allocation

The evolutionary concept that organisms possess a finite energy budget; allocating energy to one function (such as reproduction) decreases the energy available for other functions (growth, maintenance, survival).

Semelparity vs. Iteroparity

Semelparity refers to organisms that experience a single reproductive event in their lifetime before dying; iteroparity refers to organisms that undergo multiple reproductive events across their lifetime.

Monocarpic vs. Polycarpic Plants

Monocarpic plants flower and set seed only once before dying; polycarpic plants flower and set seed multiple times throughout their lifetime.

Grime's CSR Triangle

A plant life-history framework based on combinations of stress (external resource constraints restricting biomass production) and disturbance (destruction of biomass): Competitive (low stress, low disturbance), Stress-tolerant (high stress, low disturbance), and Ruderal (low stress, high disturbance).

E-P-O Life History Approach

A life-history classification based on trade-offs among juvenile survivorship, fecundity, and age at maturity: Opportunistic (low survival, low fecundity, early maturity), Periodic (low survival, high fecundity, late maturity), and Equilibrium (high survival, low fecundity, late maturity).

Population

A group of individuals of a single species inhabiting a specific area at the same time.

Absolute Density vs. Ecological Density

Absolute density is the number of individuals per unit area of total space; ecological density is the number of individuals per unit area of suitable habitat.

Numerical Response

A change in predator population density in response to changes in prey density, caused either by reproduction (creating a time lag) or aggregative dispersal (tracking prey with no time lag).

Small-Scale Distribution Patterns

Local spatial patterns of individuals in a population: Random (neutral interactions), Regular (antagonistic interactions or local resource depletion), and Clumped (mutual attraction, social grouping, or patchy resources).

Metapopulation

A group of spatially separated subpopulations occupying distinct habitat patches that are interconnected by the dispersal of individuals.

Self-Thinning

A density-dependent process in growing plant populations where individual biomass increases while overall population density progressively declines due to intraspecific competition.

Rabinowitz's Seven Forms of Rarity

A classification scheme defining rarity versus commonness through eight combinations of geographic range (extensive vs. restricted), habitat tolerance (broad vs. narrow), and local population size (large vs. small).

SARA Risk Categories

Conservation status designations under Canada's Species at Risk Act: Extinct ($X$), Extirpated ($XT$), Endangered ($E$), Threatened ($T$), Special Concern ($SC$), and Not At Risk ($NAR$).

Cohort Life Table vs. Static Life Table

A cohort life table tracks a group of individuals born simultaneously from birth to death; a static life table records the age at death of a large sample of individuals during a narrow snapshot in time.

Survivorship Curves

Plots showing survivor numbers against age: Type I (high juvenile survival, mortality in older ages), Type II (constant mortality rate across all ages), and Type III (high juvenile mortality, followed by high subsequent survival).

Frequency-Dependent Selection (Sex Ratios)

An evolutionary process where the fitness of a phenotype depends on its frequency in the population, maintaining a $1:1$ sex ratio because producing the rarer sex yields higher per capita reproductive success.

BIDE Population Dynamics Model

The demographic framework defining future population size as $N_{t+1} = N_t + B + I - D - E$, or per capita rates $N_{t+1} = N_t + N_t(b + i - d - e)$.

Density-Dependent vs. Density-Independent Factors

Density-dependent factors (competition, predation, parasites) change their per capita effect on birth or death rates as population density shifts; density-independent factors (abiotic storms, floods) exert effects regardless of population density.

Net Reproductive Rate ($R_0$ in Demography)

The average number of female offspring produced by an individual female over her entire lifetime, calculated as $R_0 = \sum l_x m_x$.

Generation Time ($T$)

The average age at which a female gives birth to her offspring, calculated as $T = \frac{\sum x l_x m_x}{R_0}$.

Per Capita Rate of Increase ($r$)

The average contribution of each individual to population growth per unit time ($r = b - d$ or $r = \frac{\ln(R_0)}{T}$); positive values indicate growth, zero indicates stability, and negative values indicate decline.

Geometric Rate of Increase ($\lambda$)

The ratio of population size between consecutive time steps ($\lambda = \frac{N_{t+1}}{N_t}$), used to model discrete population growth in organisms with pulsed reproduction and non-overlapping generations ($N_t = N_0 \lambda^t$).

Exponential vs. Logistic Growth

Exponential growth occurs under unlimited resources following a J-shaped curve ($\frac{dN}{dt} = rN$); logistic growth incorporates resource limitation and carrying capacity $K$, producing an S-shaped curve ($\frac{dN}{dt} = r_{max}N\left(1 - \frac{N}{K}\right)$).

Carrying Capacity ($K$)

The maximum population size of a species that a specific local environment can sustain indefinitely without resource exhaustion.

Maximum Sustainable Yield (MSY)

The theoretical maximum harvest rate of a population that can occur without reducing long-term population growth, occurring at half the carrying capacity ($\frac{K}{2}$) where population growth rate ($\frac{dN}{dt}$) peaks.

Horizontal vs. Vertical Disease Transmission

Horizontal transmission is the transfer of a pathogen among individuals of the same generation; vertical transmission is the direct passage of a pathogen from mother to offspring before or during birth.

Basic Reproduction Number ($R_0$ in Disease Ecology)

The average number of secondary infections generated by one infectious host in an entirely naive population without intervention, calculated as $R_0 = \frac{\beta N}{\nu + d + r}$.

Herd Immunity Threshold ($H^*$)

The minimum proportion of a population that must be immune to prevent sustained pathogen transmission, calculated as $H^* = 1 - \frac{1}{R_0}$.

Compartment Models

Mathematical epidemic models that categorize hosts into distinct infection-status compartments—such as Susceptible ($S$), Infected ($I$), and Recovered/Immune ($R$)—to track transitions and disease spread.