Island Life Midtern

Continental crust

Thick and less dense crust that usually sits higher than oceanic crust

Oceanic crust

Thin and denser crust that usually sits lower and is recycled by plate tectonics

Continental island

An island formed from continental crust and often once connected to a mainland

Oceanic island

An island that forms in the ocean basin usually through volcanism

Hotspot

A relatively fixed source of volcanism where magma rises from the mantle

Mantle plume

A column of hot rock rising through the mantle that can create hotspot volcanoes

Convergent boundary

A plate boundary where plates move toward each other

Divergent boundary

A plate boundary where plates move apart and new crust forms

Subduction

The process where oceanic crust becomes too dense and sinks beneath other crust into the mantle

Island arc

A chain of volcanic islands formed above a subduction zone

Barrier island

A low sandy island shaped by erosion and deposition and often rearranged by storms

Seismic waves

Waves from earthquakes that help scientists infer the structure of Earths interior

Uniformitarianism

The idea that the same geological processes operating now also operated in the past

Fringing reef

A coral reef attached closely to the shore of a volcanic island

Barrier reef

A coral reef separated from land by a lagoon as the island subsides

Atoll

A ring shaped coral reef left after a volcanic island sinks below sea level

Wallaces Line

A sharp biogeographic boundary separating very different animal groups in nearby regions

Common ancestor

An ancestral population from which different species descend

Natural selection

The process in which traits that improve survival or reproduction become more common over time

Mutation

A random change in DNA that creates new genetic variation

Gene flow

The movement of genes between populations through migration and reproduction

Reproductive isolation

A situation where two populations can no longer successfully interbreed

Speciation

The formation of new species

Adaptive radiation

Rapid diversification of one lineage into many species with different ecological roles

Endemic

Native to and restricted to one place

Island biogeography

The study of the distribution and diversity of life on islands

Immigration

The arrival of a species not currently present on an island

Extinction

The disappearance of a species from an island

Dynamic equilibrium

A condition where species number stays about the same while species identities change

Species turnover

The replacement of some species by others through immigration and extinction

Species richness

The number of different species in a place

Species area relationship

The pattern that larger areas usually support more species

Rescue effect

The reduction of extinction risk when new immigrants reinforce a small population

Target effect

The idea that larger islands receive more colonists because they are easier to find

Colonization

The successful arrival and establishment of a species in a new place

Founder effect

Genetic differences caused when a new population begins with only a few individuals

Genetic drift

Random changes in allele frequencies that are strongest in small populations

Genetic bottleneck

A sharp reduction in population size that removes genetic variation

Dispersal

Movement of individuals that can affect gene flow across space

Habitat selection

Dispersal to find better habitat or avoid crowding or inbreeding

Kin selection

Dispersal that helps relatives by reducing competition with them

Bet hedging

Spreading individuals across places to reduce the risk that one bad event wipes out the whole population

Ecological island

A habitat patch isolated by unsuitable surroundings even if it is not surrounded by water

Carrying capacity

The maximum population size or species load an environment can support

r selected species

Species that reproduce quickly and are often early colonizers

K selected species

Species adapted to living near carrying capacity with slower growth and stronger competition

Alternative stable states

Different stable ecological outcomes that can exist under similar conditions

Coral reef subsidence theory

Darwins idea that volcanic islands sink while coral keeps growing upward near the surface

Hotspot chain

A line of volcanoes formed as a tectonic plate moves over a fixed hotspot

Oceanic crust recycling

The process where oceanic crust forms, cools, becomes denser, and is eventually subducted

Geographic isolation

Physical separation of populations that reduces gene flow and can promote speciation

Mainland source pool

The set of species on the mainland that can potentially colonize an island

Non traditional island

Any isolated habitat patch like an oasis or forest fragment that acts like an island biologicall