With reference to the threat to Earth's biodiversity, consider the following statements: 1. Currently, the world is witnessing the 'Sixth Mass Extinction' which is slower than the previous five episodes. 2. Quagga and thylacine are now extinct. Which of the statements given above is/are correct?
Earth is currently experiencing a biodiversity crisis.
Recent estimates suggest that extinction threatens up to a million species of plants and animals, in large part because of human activities such as deforestation, hunting, and overfishing. Today, extinctions are occurring hundreds of times faster than they would naturally.
The previous five mass extinction episodes are:
Ordovician-Silurian extinction - 444 million years ago.
Late Devonian extinction - 383-359 million years ago.
Permian-Triassic Extinction - 250 million years ago.
Triassic-Jurassic Extinction: 210 million years ago.
Cretaceous-tertiary Extinction: 65 Million Years Ago.
The Cretaceous-Paleogene extinction event is the most recent mass extinction and the only one definitively connected to a major asteroid impact.
Some 76 per cent of all species on the planet, including all nonavian dinosaurs, went extinct during this period.
During the long period (>3 billion years) since the origin and diversification of life on earth, there were five episodes of mass extinction of species. The ‘Sixth Extinction’ presently in progress is different from the previous episodes in the rates; the current species extinction rates are estimated to be 100 to 1,000 times faster than in the pre-human times and our activities are responsible for the faster rates. Ecologists warn that if the present trends continue, nearly half of all the species on earth might be wiped out within the next 100 years. Hence, statement 1 is incorrect.
Some examples of recent extinctions include the dodo (Mauritius), quagga (Africa), thylacine (Australia), Steller’s Sea Cow (Russia) and three subspecies (Bali, Javan, Caspian) of the tiger. The last twenty years alone have witnessed the disappearance of 27 species. Hence, statement 2 is correct.