Animals

Birds are bipedal (two legs), endothermic (warm-blooded), vertebrate animals (with backbones) that are an important part of the animal kingdom and food chain. Birds reproduce offspring through external reproduction, known as laying eggs. There are around 10,000 living species, and they inhabit ecosystems across the globe, from the Arctic to the Antarctic. Birds range in size from the 5 cm (2 in), such as the Bee Hummingbird, to the 2.7 m (8 ft 10 in), like the Ostrich. Also, birds are winged, in order to fly, hunt, migrate and travel. The fossil records indicate that birds evolved from dinosaurs during the Jurassic period, around a million years ago, and the earliest known bird is the Late Jurassic Archaeopteryx. Most paleontologists (people that study the developing history of life on Earth) regard birds as the only species of dinosaurs that survived the Cretaceous–Tertiary extinction event. Why do you think that birds could have survived this extinction event over other large species of dinosaurs? Also, what kind of physical characteristics could have helped birds to survive? Give some examples of birds.