BIOL 327 Exam Preparation – Final Notes: Sampling, Ecology, and Distribution

Comprehensive practice flashcard set covering sampling methods, abiotic and biotic distribution factors, population growth models, predator-prey dynamics, herbivory, mutualism, and landscape ecology for BIOL 327.

Ecologist Sampling Purpose

To provide an estimate of the population size with the smallest confidence limits at the lowest cost.

Systemic Sampling

A method where samples are collected at regular intervals, such as traps placed every $5\,\text{m}$ along a transect line.

Systemic Sampling Advantage 1

It is easier than random sampling.

Systemic Sampling Advantage 2

It is desirable when one needs to sample evenly across an entire habitat.

Systemic Sampling Disadvantage

It often produces biased results.

Simple Random Sampling

A sampling method where every sample unit has an equal probability of being selected.

Simple Random Sampling Advantage

The simplest way to achieve an unbiased sample.

Simple Random Sampling Disadvantage

If the sample size is too small, it might miss out on some environment types altogether.

Stratified Random Sampling

A method where the area is divided into different strata and each stratum is sampled at random.

Stratified Random Sampling Advantage 1

Ensures all habitat types are represented.

Stratified Random Sampling Advantage 2

Reduces sampling bias.

Stratified Random Sampling Advantage 3

Often gives more precise estimates.

Stratified Random Sampling Example

Sampling where tuatara occur in rocky vs. non-rocky habitats.

Pseudo Replications

Treating non-independent variables as if they are independent.

Pseudo Replications Statistical Error

Measurements that are grouped do not provide independent pieces of information, violating the assumption of independence.

Pseudo Replications Variance Effect

Failing to account for non-independence reduces variance, creating the illusion of a highly precise result.

Wasp Poisoning Bad Design Example

Using one treated site, one untreated site, and ten traps in each.

Wasp Poisoning Experiment Problem

Traps were subsampled, not true replicates, and site differences likely affected abundance more than poisoning.

Wasp Poisoning Better Design Replicates

Choose several sites, such as $20$ sites.

Wasp Poisoning Better Design Assignment

Randomly assign half the sites to receive poisoning so they are spatially intermingled with untreated controls.

Abiotic Limits to Distribution

The principle that species can only survive when environmental conditions fall under specific tolerance limits.

Critical Abiotic Factors

Temperature and moisture.

Habitat Stability

The requirement that a habitat provides specific conditions for survival, growth, and reproduction.

Potential Niche Overlap

The overlap of right conditions (not too hot, cold, wet, or dry) that determines where a population can persist.

Moisture Variables

Precipitation, relative humidity, and soil moisture.

Temperature Variables

MAT, summer maximum, winter soil temps, number of frost days, and season of ice cover.

Correlative Models

Models that use species occurrence data and environmental variables to predict suitable habitats.

Climatic Envelope

A predicted range of climatic variables where a species can occur, identified using correlative models.

Correlative Model Strength

Relatively easy to build and useful for predicting invasions.

Correlative Model Weakness

Correlation does not equal causation.

Mechanistic Models

Models that use physiology, tolerance limits, and development rates to predict distributions.

Argentine Ant Development Requirement

Approximately $445$ degree-days above $15.9^{\circ}\text{C}$.

Argentine Ant Model Validation

Spread occurred only where the specific degree-day requirements were met.

Biotic Influences on Distribution

Interactions with other species that can restrict distributions, expand distributions, or alter abundance.

Fundamental Niche

All climatic combinations where a species could potentially persist if no other species affected it.

Potential Niche

Another term for the fundamental niche.

Realised Niche

All the locations in the world where a species actually exists in a climate suitable for persistence.

Facilitation

Any interaction that has a positive effect on the receiving party.

Mutualism

A positive interaction where both parties benefit through resource exchange or services.

Commensalism

A neutral interaction in facilitation where one party benefits and the other is unaffected.

Antagonistic Interaction

A negative interaction in terms of the effect on one party.

Nurse Plants Example

The use of Manuka and Kohuhu in restoration ecology to benefit planted natives.

Manuka and Kohuhu Benefit 1

Reduce frost damage.

Manuka and Kohuhu Benefit 2

Reduce sun exposure.

Manuka and Kohuhu Benefit 3

Reduce grass competition.

Manuka and Kohuhu Benefit 4

Improve moisture availability.

Lichens Composition

Fungi that have algae growing within them.

Lichen Resource Exchange

The lichen receives sugars, and the algae receives water and physical protection.

Algae Independence

Most algae can live without the fungus, but their habitat range is greatly enhanced as a lichen.

Competition Effect

Both species experience negative effects, often restricting their realised niches.

Wethey (2002) Study

Observed competition between $Chthamalus\,fragilis$ and $Semibalanus\,balanoides$.

Semibalanus balanoides Competition Result

Outcompeted $Chthamalus$ in northern areas.

Chthamalus fragilis Transplants

When transplanted into areas lacking $Semibalanus$, it survived beyond its normal range limit.

Competition and Ranges

Competition can determine the boundaries of species ranges.

Predation and Parasitism Impact

Often have clearer and stronger effects on broad-scale and fine-scale distribution compared to other factors.

Specialist Predators

Predators that rely on a narrow range of prey, often one or a few closely related species.

Generalist Predators

Predators that feed on a wide variety of prey species.

Extent of Occurrence (EOO)

The total area enclosed by the outermost known occurrences of a species.

EOO and Extinction Risk

A small EOO indicates a greater extinction risk.

Area of Occupancy (AOO)

The area actually occupied within the geographic range.

AOO Indicator Value

Considered a better indicator of species presence than EOO.

EOO Drawback

It includes a lot of unoccupied area.

AOO Sensitivity

The value of the AOO reduces as the resolution of the subunits becomes finer.

Rapport’s Rule

Species at higher latitudes tend to have larger geographic ranges than species in the tropics.

Rapport’s Rule Climatic Explanation

Greater climatic variability at high latitudes.

Rapport’s Rule Glaciation Explanation

Better dispersal following glaciation.

Rapport’s Rule Ecology Explanation

Less competition and greater ecological generalisation at high latitudes.

Density-Dependent Population Growth

Population growth limited by resources as density increases, causing growth to slow and stabilize.

Exponential Growth Model

Density-independent population growth occurring when resources are unlimited.

Exponential Growth Rate

The per-capita growth rate remains constant.

Exponential Growth Curve

Produces a $j$-shaped curve.

Exponential Growth Example

Invasive species immediately after introduction.

Logistic Growth Model

Density-dependent population growth that slows as it approaches carrying capacity.

Logistic Growth Density Transition

Growth is rapid at low density, then slows.

Carrying Capacity (K)

The level at which a population stabilizes in a logistic growth model.

Logistic Growth Curve

Produces an $s$-shaped curve.

Logistic Growth Example

Deer populations.

Contest Competition Model

A model where dominant individuals monopolize resources, resulting in a fixed number of successful individuals.

Contest Competition Feature

Population tends towards a stable carrying capacity with a fixed number of individuals.

Contest Competition Example

Territorial birds and mammals.

Scramble Competition Model

A model where resources are shared among all individuals, causing severe competition at high densities.

Scramble Competition High Density Effect

Individuals receive fewer resources, potentially leading to population crashes or boom-and-bust cycles.

Scramble Competition Low Survival Cause

Occurs when densities become extremely high.

Scramble Competition Example 1

Caterpillars feeding on a limited host plant.

Scramble Competition Example 2

Insect outbreaks.

Allee Effects

A phenomenon where population growth is negative at low density.

Allee Effect Cause 1

Difficulty finding mates.

Allee Effect Cause 2

Reduced group defense.

Allee Effect Cause 3

Poor cooperative survival.

Allee Effect Consequences

Small populations risk extinction even without harvesting and create unstable equilibria.

Lotka–Volterra Predator–Prey Model

A mathematical model describing predator–prey population dynamics.

Lotka–Volterra Prey Assumption

Prey grow exponentially in the absence of predators.

Lotka–Volterra Predator Assumption

The predator population depends on the prey, and consumption increases with prey abundance.

Lotka–Volterra Prediction

Predator and prey populations cycle through time.

Lotka–Volterra Classic Example

Lynx–hare dynamics.

Predation Rate

The number or proportion of prey consumed by predators per unit time.

Predation Rate Expression 1

Number of prey killed per predator per unit time.

Predation Rate Expression 2

Total prey killed per unit area per unit time.

Direct Observation of Predation

Watching predator–prey interactions and recording kills.

Direct Observation Usage

Often used for large, visible predators.