Ecology and Population Biology Lecture Notes

Comprehensive vocabulary flashcards covering organismal adaptations, life history strategies, population ecology, demographic equations, predator-prey dynamics, and interspecific competition models.

Organismal Ecology

The study of how an individual organism's behavior, physiology, and morphology are adapted to environmental and biotic factors.

Ecological Niche

The unique "job description" of a species, encompassing its life history, habitat requirements, ecological role, biotic interactions, geographic range, impacts on resource abundance, and mortality factors.

Activity Space

The range of environmental conditions (wide or narrow) that best supports the normal activity of an organism within its habitat.

Acclimation

Reversible morphological or physiological adjustments made by an organism in response to environmental conditions, such as salmon smolts excreting excess water and taking in ions in freshwater while adults pump out $Na^+$ and $K^+$ in saltwater.

Developmental Response

Nonreversible morphological or behavioral changes occurring in juvenile organisms in response to environmental cues, such as density-dependent changes in desert locusts.

Microhabitat Selection

The active selection of microenvironments that match an organism's activity space, such as iguanas maintaining a body temperature of $39\text{--}43^{\circ}\text{C}$ in Mojave air temperatures of $-7\text{ to }60^{\circ}\text{C}$ or kangaroo rats using burrows at $20\text{--}50^{\circ}\text{C}$.

Dormancy

Reversible physiological changes in metabolism, cold tolerance, and nutrient or water storage across life stages (microbial cysts, seeds, invertebrates, vertebrates) until favorable conditions return.

Biological Fitness

An organism's ability to produce surviving offspring, where a greater number of surviving offspring reflects higher fitness.

Optimal Foraging Theory (OFT)

An ecological framework stating that organisms forage to maximize energy intake while minimizing costs in energy and time spent, leaving more energy for reproduction.

Law of Diminishing Returns (in Foraging)

The principle that feeding efficiency decreases over time spent foraging as resources in a patch become depleted or harder to capture.

Central Place Foraging

A foraging model predicting how long an animal foraging from a central home location searches before returning, balancing the costs of excess travel time (leaving too early) against excess search time (staying too late).

Resource Allocation

The distribution of limited energy among survival, growth, and reproduction, requiring trade-offs such as current survival versus future fecundity and adult survival versus parental care.

Flashy Rivers Life History Strategy

An adaptive strategy characteristic of frequently disturbed river habitats, marked by early maturity and the production of many small seeds that require bare soil to germinate (e.g., willows, cottonwoods, cattails).

Stable Rivers Life History Strategy

An adaptive strategy found in stable aquatic environments, characterized by long lifespans, fewer and larger seeds, vegetative sprouting, and shade-tolerant seedlings (e.g., elm, ash, walnut).

Competitors (Grime's CSR Theory)

Plant species adapted to low disturbance and low stress that have long lifespans and allocate the majority of their energy to vegetative growth and spread rather than high seed production.

Stress-Tolerators (Grime's CSR Theory)

Long-lived plant species adapted to high-stress, low-disturbance environments that allocate significant energy to resource storage.

Population Structure

The abundance, density, spatial distribution, and demography (such as age classes and sex ratios) of individuals within a interbreeding gene pool.

Subpopulations

Spatially distinct segments of a population that are separated by environmental barriers but maintain occasional gene exchange.

Uniform Dispersion

A spatial distribution where individuals are evenly spaced across an area, typically resulting from strong agonistic or territorial interactions.

Clumped Dispersion

The most common spatial distribution pattern, where individuals aggregate in dense groups due to uneven resource distribution or strong gregarious interactions.

Demography

The study of factors and statistical parameters that affect the growth, structure, and regulation of populations.

Arithmetic Growth

Population growth that occurs by constant addition over time, characterized by a constant slope ($\frac{\Delta N}{\Delta t} = m$) and the equation $N_t = mt + N_0$.

Exponential Growth

Continuous population growth by a constant per-capita rate of increase ($r$), described by $\frac{\Delta N}{\Delta t} = N r$ and $N(t) = N_0 e^{rt}$, where the absolute addition of individuals increases with population size.

Geometric Growth

Discrete-interval population growth (such as pulsed annual breeding seasons) modeled using the finite rate of increase ($\lambda$) via the formula $N_t = N_0 \lambda^t$, where $\lambda = \frac{N_t}{N_{t-1}}$.

Age-Specific Mortality Rate ($m_x$)

The proportion of individuals dying within a specific age class $x$, calculated from life tables as $m_x = \frac{D(x)}{S(x)}$.

Survivorship Rate ($l_x$)

The proportion of the original cohort surviving from birth to the beginning of age class $x$, calculated as $l_x = \frac{S(x)}{S(0)}$.

Cohort Life Table

A life table constructed by following a single cohort of individuals born at the same time from birth until the death of the last individual.

Static Life Table

A life table constructed from a cross-sectional "snapshot" of survival and reproductive output across all age classes within a population at a single point in time.

Net Reproductive Output ($R_0$)

The mean number of offspring produced by an individual over its lifetime, calculated as $R_0 = \sum l_x b_x$.

Intrinsic Growth Rate ($r_m$)

The per-capita maximum potential rate of increase of a population, estimated using generation time ($T$) and net reproductive output as $r_m = \frac{\ln(R_0)}{T}$.

Doubling Time ($t_d$)

The time required for a population to double in size, calculated as $t_d = \frac{\ln(2)}{r_m}$ or approximated using the Rule of 70 ($t_d \approx \frac{70}{\text{interest rate}}$).

Carrying Capacity ($K$)

The maximum population size ($N$) of a species that the available resources of a habitat can sustain indefinitely.

Density-Dependent (DD) Factors

Ecological factors whose per-capita impact on mortality or birth rates varies with population density, capable of stabilizing a population around carrying capacity.

Density-Independent (DI) Factors

Ecological factors (such as abiotic disturbances and weather events) whose per-capita impact is unrelated to population density; they cannot stabilize a population.

Logistic Growth

Density-dependent population growth modeled by $\frac{\Delta N}{\Delta t} = N r_{\max} \left(1 - \frac{N}{K}\right)$, where the growth rate slows as $N$ approaches $K$, peaking at $\frac{K}{2}$.

r-Selected Species

Species adapted for rapid exponential growth in disturbed habitats, characterized by short lifespans, early sexual maturity, small body size, minimal parental care, high dispersal, and a large percentage of energy allocated to reproduction.

K-Selected Species

Species adapted to stable, competitive environments near carrying capacity, characterized by long lifespans, delayed maturity, large body size, extensive parental care, and lower reproductive output.

Limit Cycles

Permanent or repeating cyclic population fluctuations caused by time delays in density-dependent regulation combined with a high intrinsic growth rate ($r$), leading to overshooting and undershooting carrying capacity.

Charles Elton

Ecologist known as the "Father of Animal Ecology" who documented 10-year population cycles in Canadian lynx and snowshoe hares using 90 years of Hudson's Bay Company furbearer records.

Biocontrol

The management of agricultural pests by introducing or maintaining natural predators, parasites, or pathogens to prevent prey populations from undergoing explosive exponential growth.

Prey Equilibrium (Lotka-Volterra)

The predator density (denoted as $\hat{P} = \frac{r}{c}$) at which prey population growth equals zero ($\frac{\Delta R}{\Delta t} = 0$); prey populations decline above this predator threshold and increase below it.

Predator Equilibrium (Lotka-Volterra)

The prey density (denoted as $\hat{R} = \frac{m}{ac}$) necessary to sustain a stable predator population ($\frac{\Delta P}{\Delta t} = 0$); predator populations increase above this prey threshold and decrease below it.

Lotka-Volterra Predator-Prey Model

A mathematical model describing coupled cyclic oscillations between prey ($\frac{\Delta R}{\Delta t} = Rr - RPc$) and predators ($\frac{\Delta P}{\Delta t} = PRca - Pm$), governed by prey birth rate ($r$), capture efficiency ($c$), conversion efficiency ($a$), and predator mortality ($m$).

Huffaker's Experiment

A laboratory study testing predator-prey cycling using predatory and herbivorous mites placed on an experimental grid of oranges and rubber balls.

Liebig's Law of the Minimum

A principle formulated in 1840 stating that total biomass and yield are controlled not by the total pool of resources, but by the scarcest limiting resource relative to demand.

Limiting Resource

An essential resource whose availability is reduced by use and sets the upper limit on population growth and carrying capacity (typically $N$, $P$, and $K$ in terrestrial habitats; $N$ and $P$ in freshwater; and $N$ and $Fe$ in marine environments).

Exploitative Competition

Indirect competition ("scramble competition") in which one organism reduces the abundance of a shared limiting resource more rapidly and efficiently than another.

Interference Competition

Direct competition where an organism actively blocks or prevents another from accessing a shared resource through aggressive behavioral interactions or chemical allelopathy.

Competitive Exclusion Principle (Gause 1932)

The ecological principle stating that two species competing for the exact same limiting resource in an identical niche cannot coexist stably, resulting in the dominant competitor driving the inferior competitor to local extinction.

Competition Coefficient ($\alpha_{1,2}$)

A parameter in the Lotka-Volterra competition model ($\frac{\Delta N_1}{\Delta t} = N_1 r_{\max 1} \left[1 - \frac{N_1 + \alpha_{1,2} N_2}{K_1}\right]$) expressing the per-capita inhibitory effect of species 2 on the resource share of species 1.

Niche Splitting

The evolutionary or behavioral divergence of competing species into different microhabitats or resource spectrums, which reduces competition and allows coexistence.

Intermediate Disturbance Hypothesis

An ecological hypothesis (formulated by Tansley and Connell) stating that species diversity peaks at intermediate disturbance frequencies and intensities, where both dominant and inferior competitors coexist.