Unit 2: Ecological Disruptions & Tolerance (2.4-2.7)

ecological tolerance

The ability of a species to survive and reproduce under a range of environmental circumstances (generalists are more tolerant compare to specialists)

range of tolerance

Range of chemical and physical conditions that must be maintained for populations of a particular species to stay alive and grow, develop, and function normally

natural disturbances/disruptions

all natural events that destroy or damage an ecosystem; fires, hurricanes, tornadoes, droughts, floods

anthropogenic disturbances/disruptions

Human-caused disturbances to ecosystems. Often negatively impacts biodiversity. Timber harvesting, pollution, overgrazing, introducing invasive species, and development.

periodic

describes an event that occurs or repeats at regular intervals (seasons, night & day)

episodic

describes an event that happening in parts or segments or that kicks off a flow of related events (eutrophication, overhunting by humans)

random

something that occurs randomly (hurricanes, lightening strikes, etc.)

migration

Movement of organisms from one habitat to another. Sometimes permanent (when their habitat is destroyed or disturbed) or temporary (for mating, feeding, or seasonal reasons)

sea level

The average level of the ocean's surface at any given time. Has changed significantly over time based on amount of glacial ice and polar ice.

geologic time scale

scale used by paleontologists to represent evolutionary time

resistance

measure of how much a disturbance can affect the flow of energy and matter in an ecosystem. ecosystems with high resistance are not as vulnerable to natural and anthropogenic disturbances

resilience

the rate at which an ecosystem returns to its original state after a disturbance. the more resilient, the faster an ecosystem returns to its normal state after a disturbance

Adaptation

A characteristic that improves an individual's ability to survive and reproduce in a particular environment.

genetic diversity

a measure of the genetic variation among individuals in a population (higher gen. diversity leads to greater rate of evolution)

Genotype

An organism's genetic makeup

Phenotype

An organism's physical appearance, or visible traits.

natural selection

A process in which individuals that have certain inherited traits tend to survive and reproduce at higher rates than other individuals because of those traits. Leads to evolution of new traits (microevolution) and new species (macroevolution)

Evolution

Changes in a species over time driven by natural selection. Can lead to new traits or entirely new species. INDIVIDUALS DO NOT EVOLVE. SPECIES EVOLVE.

Speciation

the formation of new and distinct species in the course of evolution.

Species

A group of similar organisms that can breed and produce fertile offspring. Different species cannot breed with each other.

reproductive isolation (sympatric speciation)

Differences in behavior or morphology that prevent organisms from breeding with each other (diff. mating calls in birds or diff. structures in flowers in plants)

geographic isolation (allopatric speciation)

two populations are separated physically by geographic barriers such as rivers, mountains, or stretches of water. this prevents them from breeding with each other and leads them to evolve into different species

ecological succession

gradual change in living communities that follows a disturbance

primary succession

succession that occurs on surfaces where no soil exists (bare rock being colonized by moss & lichen, broken down into soil, & eventually colonized by grasses and shrubs)

secondary succession

Succession following a disturbance that destroys a community without destroying the soil (often times a fire or windstorm)

pioneer species

Hardy, first species to populate an area during primary or secondary succession (moss & lichens, small grasses, shrubs, and small trees)

climax species

species that move into an area at later stages of ecological succession. slower growing, species that include large tree

keystone species

A species that has an unusually large effect on its ecosystem. It influences the survival of many other species in an ecosystem, often by creating habitats (beavers) or controlling herbivores (wolves)

indicator species

Species that serve as early warnings that a community or ecosystem is being degraded. (think of the canary in the coal mine)