Since life on Earth began, a huge number of animals have
appeared, flourished and then disappeared again. These disappearances are
called extinctions. Individual species become extinct for a variety of reasons,
including competition and habitat changes. At least five times in the past
there have been mass extinctions, where large numbers of animal species have
died out in a short period.
Dinosaurs became extinct 65 million years ago, at the end of the
Mesozoic era. Their disappearance has been linked to a massive meteor strike,
which left an vast crater beneath the Gulf of Mexico. Scientists think the gas
and dust from this impact filled the atmosphere, blotting out the sun for
centuries. In that time, 70 per cent of all animals died out, including the
dinosaurs.
Many islands have unique species, found nowhere else. If new
predators are introduced, they have no way of escaping. This makes them
especially vulnerable to extinction. One way of protecting island animals is to
make their homes nature reserves. This giant tortoise is from the Galapagos
Islands, which are protected by the government of Ecuador.
Animals facing extinction in the wild can be saved by increasing
their numbers in zoos. Pandas do not usually breed well in captivity, but in
recent years the number of captive births has risen considerably. This is
partly due to increased cooperation between zoos, with more loaning out their
male or female pandas to form new pairs around the world.
