Behavioral Ecology and Population Ecology: Key Terms and Concepts

Behavioral Ecology

Proximate and Ultimate Causation

Understanding animal behavior involves distinguishing between proximate and ultimate causes:

• Proximate causation: Refers to the immediate, mechanistic causes of behavior (e.g., hormonal, neurological, genetic factors).

• Ultimate causation: Refers to the evolutionary reasons why a behavior occurs, often related to fitness and survival.

Mating Systems

• Polygamy: One individual mates with multiple partners.

• Promiscuity: No lasting pair bonds; individuals mate with several others.

• Monogamy: One male and one female form a pair bond.

• Extra-pair copulation: Mating outside the primary pair bond.

Example: Prairie Vole exhibits monogamous behavior, while Meadow Vole is more promiscuous.

Social Behavior and Hormones

• Consoling behavior: Actions that comfort distressed individuals, often observed in social mammals.

• Oxytocin: A hormone associated with bonding and social behaviors.

• Reciprocal social behavior: Behaviors exchanged between individuals, often related to inclusive fitness.

Dispersal Behavior

Movement of individuals away from their birthplace, affecting gene flow and population structure.

Sexual Selection

• Intrasexual selection: Competition among individuals of the same sex for mates (e.g., American Moose).

• Intersexual selection: Mate choice by the opposite sex.

• Runaway sexual selection: Traits become exaggerated due to preference (e.g., Scissor-tailed flycatcher).

• Fitness traits: Traits indicating health or genetic quality (e.g., American red squirrel, Barn owl).

Kin Selection and Altruism

• Kin selection: Favoring relatives to increase inclusive fitness.

• Altruism: Behavior benefiting others at a cost to oneself.

• Inclusive fitness: Sum of direct and indirect fitness.

• Direct fitness: Own offspring produced.

• Indirect fitness: Helping relatives reproduce.

• Reciprocal altruism: Helping others with expectation of future return.

• Kin care: Parental or familial care for relatives.

• Coefficient of Relatedness (r): Probability that two individuals share genes by descent.

Hamilton’s Rule:

$r \times B > C$ Where r = coefficient of relatedness, B = benefit to recipient, C = cost to actor.

Levels of Ecological Study

• Organismal

• Population

• Community

• Ecosystem

• Biosphere

Limits to Tolerance

• Survivorship: Proportion of individuals surviving to a given age.

• Fitness: Reproductive success of an organism.

Example: Coconut palm and Acai palm have different tolerance limits for environmental factors.

Ecological Niche

• Grinnellian niche: Habitat requirements.

• Eltonian niche: Role in ecosystem (e.g., trophic interactions).

• Hutchinsonian niche: Multidimensional space of environmental factors.

• Fundamental niche: Potential range without competition.

• Realized niche: Actual range with biotic interactions.

• Impact niche: Effects on environment.

• Requirement niche: Needs for survival.

Abiotic and Biotic Niche Factors

• Abiotic: Non-living factors (e.g., temperature, moisture).

• Biotic: Living factors (e.g., competition, predation).

Productivity and Biomass

• Biomass: Total mass of living organisms.

• Aboveground biomass: Mass of living plants above soil.

• Primary productivity: Rate at which plants produce biomass.

• Net primary productivity (NPP): Biomass available to consumers.

• Evapotranspiration: Water loss via evaporation and plant transpiration.

Climate and Biomes

Climatograph and Biome Types

• Biomes classified by precipitation and temperature.

• Climatographs plot these variables to define biome types.

Climate Factors

• Solar radiation angle of incidence: Affects temperature and seasonality.

• Seasonality: Caused by Earth's axis tilt.

• Key latitudes: Arctic Circle, Tropic of Cancer, Tropic of Capricorn, Antarctic Circle.

• Atmospheric structure: Layers of atmosphere affect climate.

• Adiabatic heating and cooling: Temperature changes due to pressure changes.

• Atmospheric convection cells: Hadley, mid-latitude, and polar cells drive global climate.

• Coriolis effect: Deflects wind patterns.

• Ocean currents: Move heat and affect climate.

• Local climate: Coastal vs. interior climates; orthographic lifting causes precipitation.

Population Ecology

Demography

• Survivorship curves: Graphs showing survival rates at different ages.

• Fecundity: Reproductive output.

• Net reproductive rate (R): Average number of offspring per individual.

Per capita rate of population increase (r):

$r = \frac{dN}{dt} \div N$ Where N = population size, dN/dt = change in population size over time.

• r intrinsic: Maximum rate under ideal conditions.

• r maximum: Highest possible rate.

• r actual: Observed rate.

• Relationship to R: R > 1 means population grows; R < 1 means it declines.

Population Growth Models

• Exponential growth: Population grows without limits.

$\frac{dN}{dt} = rN$

• Logistic growth: Population growth slows as it approaches carrying capacity.

$\frac{dN}{dt} = rN \left(1 - \frac{N}{K}\right)$ Where K = carrying capacity.

• High r population growth: Rapid increase, often seen in invasive species.

• Human population growth: Influenced by age-class structure and inertia.

Community Ecology

Species Interactions

• Commensalism: One species benefits, other unaffected.

• Competition: Both species harmed; can lead to extinction or niche displacement.

• Niche differentiation: Species evolve to use different resources.

• Example: Darwin’s finches (Geospiza fortis and G. fuliginosa) show niche differentiation.

• Mutualism: Both species benefit.

• Consumption: One species benefits, other harmed.

• Herbivory: Animals eat plants.

• Predation: Animals eat other animals.

• Parasitism: Parasites harm hosts.

• Endoparasites: Live inside host.

• Ectoparasites: Live outside host.

• Parasitoids: Kill host as part of life cycle.

Adaptations Against Consumption

• Cryptic coloration: Camouflage.

• Armor and weapons: Physical defenses.

• Escape behavior: Rapid movement to avoid predation.

• Schooling and flocking: Group behavior for defense.

• Defensive chemicals: Toxins and repellents.

Specialization and Generalization

• Specialization: Narrow ecological niche.

• Generalization: Broad ecological niche.

Interaction Type	Effect on Species 1	Effect on Species 2	Example
Commensalism	+	0	Birds nesting in trees
Competition	-	-	Darwin's finches
Mutualism	+	+	Bees and flowers
Consumption	+	-	Predation, herbivory, parasitism

Additional info: Academic context was added to clarify definitions, examples, and equations for population growth and Hamilton's Rule.