Ecology Final Exam

ecology

Ecology is the study of the interactions between organisms and their biotic and abiotic environment.

Nutrient cycling

Nutrient cycling is an example of a(n) emergent property.

population

A group of individuals of the same species that are spatially distinct from other groups of individuals of the same species.

five important characteristics of population distributions

Geographic range, abundance, density, dispersion, and dispersal.

three types of population dispersion

Clumped: Individuals are clustered together, often near resources. Regular: Individuals are evenly spaced, often due to territoriality. Random: The spatial arrangement of individuals is unpredictable.

Abundance

Abundance refers to the total number of individuals of a species in a given area.

Density

Density refers to the number of individuals per unit area or volume.

community

A group of interacting species that occur together at the same place and time.

indirect effects

Indirect effects occur when the interaction between two species is mediated by a third species.

Trophic cascade

A predator suppresses herbivores, leading to increased plant biomass.

apparent competition

When two species that share a predator appear to compete, even if they do not directly interact.

Indirect Mutualism

Two species indirectly benefit each other through interactions with a third species.

keystone species

A species that has a disproportionately large impact on its environment relative to its abundance or biomass.

Pisaster ochraceus

A keystone predator in the intertidal zone.

dominant species

An abundant species that exerts a significant influence on other species within that community or the structure and function of an ecosystem.

ecosystem engineer

A species that significantly modifies or creates habitat.

ecosystem

A community of interacting organisms and their physical environment.

pools

Nutrients in ecosystems move between pools, which are storages of matter or energy.

Sink

The part of an ecosystem that absorbs and stores a particular substance, nutrient, or energy at a greater rate than it releases.

Fluxes

Fluxes are the movement of matter or energy within ecosystems.

Form

A nutrient's form, or chemical/physical state, affects its movement through the ecosystem and availability to organisms.

biosphere

The portion of Earth that houses all living organisms and their environments.

systems thinking

Understanding complex systems by emphasizing the interconnectedness of their parts.

positive and negative feedback

Positive feedback: Amplifies or reinforces a stimulus, creating a self-perpetuating cycle. Negative feedback: Dampens a stimulus to stabilize the system.

mechanism

A system of causally interacting parts and processes that produce one or more effects.

patterns (or phenomena)

Ecologists format observations as patterns (or phenomena) to help generate research questions.

Hypothesis

A proposed, testable explanation based on evidence.

characteristics of a good hypothesis

Explains a pattern. Contains a mechanism. Testable. Written in the present tense.

prediction

A hypothesis leads to a prediction, which is a testable statement written in the future tense.

experiment

A controlled procedure for evaluating a hypothesis by manipulating variables and observing their effects.

cause-and-effect relationship

Experiments are the only way to establish a cause-and-effect relationship.

ecological detectives

When ecologists evaluate multiple hypotheses using observations and best-fit comparisons, they are acting as ecological detectives.

Fundamental niche

The full range of environmental conditions and resources a species can potentially utilize.

Realized niche

The portion of the fundamental niche a species occupies in the presence of competition and biotic interactions.

niche partitioning

When species specialize on different resources to reduce competition.

adaptations

Traits that allow organisms to survive and reproduce in their environment.

carrying capacity

The maximum population size an environment can sustainably support.

BIDE model

The BIDE model describes changes in population size using births, deaths, immigration, and emigration.

density-dependent factors

Factors whose influence on population growth depends on the population density; examples include: Competition, Disease transmission, Predation.

density-independent factors

Factors that affect population size regardless of density.

Intrinsic rate of increase (r)

The intrinsic rate of increase (r) is a measure of a population's potential for growth under ideal conditions.

extinction risk

The probability that a population will go extinct.

ecological interaction

The relationship between two or more species in an ecosystem.

competition

Competition is a (-/-) interaction, meaning that both species are negatively affected.

types of competition

Intraspecific: Competition between individuals of the same species. Interspecific: Competition between individuals of different species.

ways competition can occur

Exploitation: Indirect competition through resource depletion. Interference: Direct competition by physically preventing access to resources.

Competitive exclusion

One species outcompetes and eliminates another.

Coexistence

Species share resources.

Lotka-Volterra competition model

Describes how competing species coexist or how one species can exclude the other.

Exploitation

An interaction where one species benefits by consuming or using another species (+/-).

Predation

Killing and consuming an animal.

Parasitism

One organism living on or within a host and deriving nutrients.

Herbivory

Consuming plants.

Omnivory

The consumption of organisms from more than one trophic level.

Top-down regulation

Consumers limiting the abundance of their prey.

Bottom-up regulation

Resources limiting the abundance of their consumers.

Lotka-Volterra Consumer-Resource model

Describes the dynamics of predator-prey interactions.

Mutualism

An interaction where both species benefit (+/+).

Facilitation

A broader term; commensalism falls under facilitation but not mutualism.

Commensalism

A relationship where one species benefits and the other is unaffected (+/0).

Benefits of mutualistic relationships

(Any of the following) Water and nutrients, Places to live, Defense against enemies, Pollination and seed dispersal.

Obligate mutualism

Necessary for survival of at least one species.

Facultative mutualism

Not necessary for survival.

Trophic mutualism

A mutualism where species exchange food or energy.

Defensive mutualism

A mutualism where one species provides protection for another in exchange for food or shelter.

Transport mutualism

A mutualism involving the transport of one species, or its gametes, by another species.

Amensalism

An interaction where one species is negatively affected and the other is unaffected (0/-).

Neutralism

An interaction where neither species is affected (0/0).

Interaction strength

The magnitude of the effect one species has on another.

Weak interaction effect

The observation that most species interactions are weak.

Biodiversity

Encompasses all living organisms, the communities and ecosystems they form, and their evolutionary diversity.

Extremophiles

Organisms that thrive in extreme conditions.

Species richness

The number of species present in a given location.

Alpha diversity (α)

The average number of species within a small, homogeneous region.

Beta diversity (β)

The difference in species composition between two habitats or communities.

Gamma diversity (γ)

The total species richness across a larger landscape or region.

Species evenness

A measure of how equally individuals are distributed among species.

Shannon-Wiener Diversity Index

Combines richness and evenness into one measure.

Functional diversity

Measures the diversity of functional traits within a community.

Phylogenetic diversity

Measures the evolutionary history of species in a community.

Genetic diversity

Measures the genetic variation within a species or population.

Global species richness estimates

Range from five million to six billion.

Heterogeneity

Variation in environmental characteristics.

Latitudinal gradient

The pattern of increasing species richness from poles to equator.

Biodiversity hotspot

A region with exceptionally high species richness and endemism.

Ecosystem services

Benefits humans receive from ecosystems. Examples include: Clean air and water, Pollination, Pest control, Climate regulation.

Succession

The process of species replacing each other over time in a community.

Climax communities

Relatively stable and represent the endpoint of succession.

Mechanisms of succession

Facilitation, Inhibition, Tolerance.

Primary succession

Occurs in habitats initially devoid of soil.

Secondary succession

Occurs in disturbed habitats that still have soil.

Disturbances

Events that disrupt the structure and function of ecosystems.

Intermediate disturbance hypothesis

The hypothesis that species diversity is maximized at intermediate levels of disturbance.

Nutrient cycles

Biogeochemical cycles that describe the movement of nutrients.

Fast carbon cycle

Involves the rapid exchange of carbon between living organisms and the atmosphere.

Slow carbon cycle

Involves the exchange of carbon between rocks, soil, and the atmosphere over long timescales.

Nitrogen fixation

The conversion of atmospheric nitrogen gas into usable forms by bacteria and archaea.

Nitrification

The conversion of ammonia to nitrite, then nitrate, by bacteria.

Denitrification

The conversion of nitrate to nitrogen gas by bacteria.

Phosphorus as a limiting nutrient

True.