Extinction describes the complete cessation of a species or higher taxon level, reducing biodiversity

  • Extinctions can occur gradually as one population of organisms evolves into something else (phyletic extinction)
  • Alternatively, a species may not leave any identifiable descendents and simply cease to exist (abrupt extinction)

It can be very difficult to determine the moment of extinction, and so most categorisations are usually done retrospectively

  • Occasionally species thought to be extinct can be rediscovered after a period of time (Lazarus taxa)

Over 99% of all species that ever lived on Earth are considered to be extinct (estimated to amount to over 5 billion species)

  • Occasionally, natural catastrophes may cause mass extinction events (large scale loss of species in relatively short period)

Case Study: Tasmanian Tiger

  • The Tasmanian tiger (Thylacinus cynocephalus) became extinct after the arrival of European settlers to Australia
  • The Tasmanian tigers would feed on introduced sheep and were subsequently hunted and poached by man
  • The loss of habitat to human development and lack of successful breeding programs led to population numbers dwindling
  • The last Tasmanian tiger died in captivity in 1936 and they were declared extinct by international standards in 1986
  • Aboriginal rock paintings suggest the Tasmanian tiger once lived on the mainland, but died out from predation / competition

Photo of a Tasmanian Tiger

tasmanian tiger