Most people know that all the animals in the world belong to one animal group or another.
The biggest bird of all, the ostrich, grows up to 2.74m tall and is so heavy, it can't fly. The tiny bee hummingbird is the smallest bird in the world and measures just 5.7cm. It's an expert at flying, beating its wings 80 times per second so that it can hover on the spot and even fly backwards. There are about 2,000 species of stick insects, some reach mammoth lengths of 36cm, making them the world's longest insects. The big blue The largest animal in the world is the blue whale.