The world today is going through the sixth largest mass extinction event in its history. As a part of GCSE Geography students will look at some of the causes of extinctions, but also what can be done to slow their rate - or even to bring some extinct species back to life.
A species is declared extinct when its last known member dies. Sometimes this happens in the wild, and it’s only after years of searching by scientists that the entire species is declared extinct. At other times it’s a rather public loss. The last known thylacine, or Tasmanian tiger, died in Hobart Zoo in 1936, just 59 days after the species was officially protected. There is limited evidence that some thylacines survived in the wild into the 1960s but little beyond that. However, the species wasn’t officially declared extinct until 1982.
A species might now be declared extinct, extinct in the wild, or just considered functionally extinct. Some species, such as the giant pangasius, are extremely threatened in the wild and possibly extinct. However, in captivity the giant pangasius is such a common species that it is often sold in supermarkets as food. It is also one of the main types of pet fish handed into rescues as they outgrow their aquariums. Functional extinction often occurs when the population of a species is too low to have enough genetic diversity for its numbers to have any hope of recovery.
Through time some species have gone extinct as the bulk of them have evolved into another distinct species. Several large scale extinctions (mass extinction events) have occurred when conditions have changed too rapidly for organisms to adapt and evolve to keep up with. The causes of these are thought to range from asteroid impacts to climate change. We are currently in the midst of another mass extinction as we lose species faster than at any other time since the Cretaceous-Tertiary Mass Extinction some 66 million years ago. That particular mass extinction is famed for the loss of the dinosaurs, but they were amongst thousands of other species that were also lost.
Try this quiz to see how well you know the causes of extinctions or what might bring about a mass extinction event.