Ecology, Disturbances, Evolution, and Succession

Ecological Tolerance

The range of environmental conditions an organism can survive and reproduce in.

Niche

A species' role in its ecosystem, including how it uses resources and interacts with other organisms.

Fundamental Niche

The full range of conditions and resources a species could use without competition or other limitations.

Realized Niche

The conditions and resources a species actually uses because of competition and other limiting factors.

Geographic Range

The total area where a species is naturally found.

Mass Extinction

A period when a large percentage of Earth's species become extinct in a relatively short time.

Anthropogenic

Caused by human activities.

Periodic Disruption (Disturbance)

A disturbance that happens regularly or predictably, such as seasonal flooding.

Episodic Disruption

A disturbance that happens occasionally but not on a regular schedule, such as a hurricane.

Random Disruption

An unpredictable disturbance that can happen without a regular pattern.

Resistance

An ecosystem's ability to remain mostly unchanged when a disturbance occurs.

Resilience

An ecosystem's ability to recover after a disturbance.

SLR (Sea Level Rise)

An increase in average ocean level, mainly caused by melting land ice and thermal expansion from warming.

Intermediate Disturbance Hypothesis

Moderate levels of disturbance can produce greater species diversity than very low or very high disturbance.

Evolution

Change in the genetic makeup of a population over generations.

Microevolution

Small genetic changes within a population or species over time.

Macroevolution

Large-scale evolutionary change over long periods that can produce new species or larger groups.

Natural Selection

Individuals with beneficial traits are more likely to survive and reproduce, making those traits more common.

Artificial Selection

Humans choose which organisms reproduce to increase desired traits.

Fitness

An organism's ability to survive and successfully reproduce.

Adaptation

An inherited trait that increases an organism's survival or reproductive success.

Mechanisms of Evolution

Processes that change allele frequencies, including mutation, gene flow, genetic drift, and natural selection.

Random Mutation

A random change in DNA that can create new genetic variation.

Gene Flow

Movement of genes between populations when individuals migrate and reproduce.

Genetic Drift

Random changes in allele frequencies, especially in small populations.

Bottleneck Effect

Loss of genetic diversity when a population suddenly becomes much smaller.

Founder Effect

Reduced genetic diversity when a new population is started by a small number of individuals.

Speciation

The formation of a new species.

Allopatric Speciation

New species form after populations become geographically separated.

Sympatric Speciation

New species form without geographic separation, usually because reproductive isolation develops.

Ecological Succession

The gradual change in the species and community of an ecosystem over time.

Primary Succession (Terrestrial)

Succession that begins in an area with no soil, such as newly exposed rock.

Secondary Succession (Terrestrial)

Succession after a disturbance where soil is still present, such as after a fire or abandoned farmland.

Pioneer Species

The first species to colonize an area during succession, such as lichens and mosses.

Early Successional Species

Fast-growing species that quickly colonize disturbed areas, such as grasses and weeds.

Mid-Successional Species

Species such as shrubs and small trees that appear as soil and ecosystem conditions improve.

Late (Climax) Successional Species

Species that dominate a mature, relatively stable community, often larger and slower-growing.

Aquatic Succession

Gradual change in an aquatic ecosystem, often as sediment and organic matter accumulate and make the water shallower.

Keystone Species

A species that has a disproportionately large effect on its ecosystem compared with its abundance.

Indicator Species

A species whose presence, absence, or health can show the environmental condition of an ecosystem.