Ethology and Population Dynamics Overview

Ethology

The study of how evolutionary processes shape inherited behaviors and how animals respond to specific stimuli.

Behavior

An animal's response to a stimulus (internal or external); subject to natural selection.

Proximate Cause

How a behavior occurs or is modified. E.g., stimulus or environmental influences during growth.

Ultimate Cause

Why a behavior occurs in terms of evolutionary advantage. E.g., survival or reproductive benefit.

Innate Behaviors

Developmentally fixed behaviors that are inherited and instinctive. Not affected by experiences.

Learned Behaviors

Behaviors influenced by environment and experiences. Show high variation in a population.

Fixed Action Pattern (FAP)

A sequence of unlearned, unchangeable acts triggered by a specific stimulus. E.g., red belly in stickleback fish.

Sign Stimulus

An external cue that triggers a behavior (e.g., the red color triggering aggression in fish).

Migration

Regular, long-distance movement triggered by environmental cues (e.g., sun position, magnetic field).

Signal

A stimulus transmitted between animals to communicate. Can be visual, auditory, tactile, electrical, chemical.

Pheromones

Chemical signals emitted by one member of a species to affect others.

Stimulus Response Chain

One behavior triggers the next in a sequence (seen in courtship).

Waggle Dance

A bee behavior communicating food location via body movement.

Directed Movements

Movements in response to stimuli.

Kinesis

Non-directional change in activity in response to a stimulus.

Taxis

Directed movement toward or away from a stimulus.

Phototaxis

Response to light.

Chemotaxis

Response to chemical signals.

Geotaxis

Response to gravity.

Imprinting

Irreversible learning occurring during a sensitive period early in life. E.g., ducklings following their mother.

Spatial Learning

Memory based on environmental layout (e.g., birds using landmarks).

Cognitive Map

A mental representation of spatial relationships.

Associative Learning

Connecting one environmental feature with another. E.g., associating bad taste with certain insects.

Social Learning

Learning by observing and imitating others. E.g., chimps using tools.

Foraging

The act of searching for and obtaining food.

Mating Behaviors

Can be monogamous or polygamous (polygyny or polyandry).

Sexual Dimorphism

Physical differences between sexes due to sexual selection.

Cooperative Behaviors

Actions that increase the survival of the group.

Altruism

Self-sacrificing behavior that benefits others' fitness at a cost to oneself. E.g., non-reproductive naked mole rats protecting the queen.

Phototropism

Directional growth of plants toward or away from light.

Photoperiodism

Development in response to day length (e.g., flowering seasonally).

Physical Defenses

Structural traits like thorns or trichomes (small hairs).

Chemical Defenses

Production of toxins or distasteful chemicals. E.g., signaling in lima beans to prepare for herbivory.

pH Sensitivity

Affects nutrient availability and flower color (e.g., hydrangeas).

1st Law of Thermodynamics

Energy can neither be created nor destroyed, only transferred.

Law of Conservation of Mass

Chemical elements are continually recycled in the environment.

2nd Law of Thermodynamics

Exchanges of energy increase the entropy of the universe.

Population

A group of individuals of the same species living in an area.

Population ecology

Analyzes the factors that affect population size and how and why it changes over time.

Density

The number of individuals per unit area.

Sampling techniques

Count individuals in small areas, average the counts, and estimate total population size.

Dispersion

The pattern of spacing among individuals within a population.

Clumped

Individuals gather in patches.

Uniform

Evenly spaced individuals, often due to territoriality.

Random

Unpredictable spacing; not common.

Demography

The study of the vital statistics of populations and how they change over time.

Life table

An age-specific summary of survival patterns in a population.

Survivorship curve

A graphical representation of a life table.

Type I

Low death rate early/middle life, high later.

Type II

Constant death rate throughout life.

Type III

High death rate early, lower for survivors.

Per capita rate of increase

The rate at which the population increases per individual.

Exponential growth

Population grows under ideal conditions (abundant resources, free reproduction).

J-shaped curve

Characteristic shape of exponential growth.

Logistic growth

The growth rate slows as population nears carrying capacity.

Carrying capacity (K)

Maximum population size an environment can support.

Life history

Traits that affect an organism's reproductive schedule and survival.

K-selection (density-dependent selection)

Traits selected in high-density, competitive environments near carrying capacity.

R-selection (density-independent selection)

Traits that maximize reproduction in low-density, low-competition environments.

Density-dependent regulation

Growth is regulated by factors that worsen with population density.

Density-independent regulation

Environmental factors affect population size regardless of density.

Community

A group of populations of different species living closely and capable of interacting.

Habitat

A place or part of an ecosystem occupied by an organism.

Ecological niche

The role and position a species has in its environment.

Fundamental niche

The potential niche of a species without limiting factors.

Realized niche

The actual niche a species occupies in the presence of limiting factors.

Interspecific interactions

Interactions between individuals of different species.

Competition

(-/-) Individuals of different species compete for limited resources.

Competitive exclusion principle

Two species competing for the same resource cannot coexist permanently.

Niche partitioning

Natural selection leads species to different patterns of resource use.

Predation

(+/−) One species (predator) kills and eats another (prey).

Cryptic coloration

Camouflage.

Batesian mimicry

Harmless species mimics a harmful one.

Müllerian mimicry

Two or more harmful species resemble each other.

Herbivory

(+/−) One organism eats part of a plant or alga.

Symbiosis

Two or more species live in direct contact.

Parasitism

(+/−) One organism benefits, the other is harmed.

Mutualism

(+/+) Both organisms benefit.

Commensalism

(+/0) One benefits, the other is unaffected.

Facilitation

(+/+ or 0/+) One species positively affects another without direct contact.

Species diversity

Variety of organisms in a community.

Species richness

Number of different species.

Relative abundance

Proportion each species contributes to the total.

Simpson's diversity index

Measures biodiversity using richness and abundance.

Invasive species

Organisms introduced to a new habitat, often without natural predators or competitors.

Keystone species

Species with a disproportionately large effect on their ecosystem despite low abundance.

Disturbance

An event that changes a community by removing organisms or altering resources.

Ecological succession

Gradual change in community composition over time.

Primary succession

Occurs in lifeless areas with no soil.

Secondary succession

Occurs where a community existed but was disturbed, soil remains.

Habitat loss

Greatest threat to biodiversity (e.g., urbanization, agriculture).

Overharvesting

Harvesting organisms faster than populations can recover.

Global change

Climate and ecological alterations (e.g., pollution, CO₂ emissions).

Biogeographical factors

Large-scale influences on diversity.

Latitude

More diversity in tropics.

Area

Larger areas have more habitats and greater diversity.

Pathogens

Disease-causing organisms/viruses.