Extinction

Extinction is the permanent loss of every living member of a species or other taxonomic group. It can result from environmental change, biological interactions, or human activity.

Extinction debt: A delayed loss of species caused by past environmental change whose effects unfold over time. Habitat destruction can commit populations to eventual extinction before their final individuals disappear.
Cretaceous–Paleogene extinction event: A mass extinction about 66 million years ago that eliminated non-avian dinosaurs and many other groups. The impact-driven event shows how a sudden global shock can end entire lineages.
Georges Cuvier: A French naturalist who established extinction as a fact through comparative anatomy and fossil evidence. His work challenged the idea that every species persisted unchanged through time.
Biodiversity loss: The decline in the variety of life across genes, species, and ecosystems. Extinction is its most final outcome, though biodiversity can decline before species vanish.
IUCN Red List: A global assessment system that classifies species by their risk of extinction. Its categories provide a widely used record of assessed extinction risk.
Allee effect: A decline in individual fitness or population growth at low population density. Small populations can shrink faster when finding mates, cooperating, or avoiding predators becomes harder.
Permian–Triassic extinction event: The largest known mass extinction, about 252 million years ago, which devastated marine and terrestrial life. Its scale illustrates how prolonged environmental disruption can produce catastrophic losses.
Mary Anning: An English fossil collector and paleontologist whose discoveries included important marine reptiles. Her fossils helped reveal vanished forms of life and the deep history of extinction.
Ecological cascade: A chain of ecological effects triggered by changes to one or more species or processes. Losing a species can alter food webs and cause further population declines.
Endangered species: A species facing a very high risk of extinction in the wild. This conservation status identifies species for which extinction risk is already severe.

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