Notochord, a flexible supporting rod along the back of an animal. It is present in all chordate animals at some stage in their development. A primitive chordate retains it throughout life. In higher vertebrate animals, the notochord is replaced before birth by a backbone.
If you feel like you just can't get away from all the flying, buzzing insects, you may be right -- insects far outnumber humans. Scientists can only estimate the number of insects on Earth. Take this quiz to find out how much you know about the multitudes of insects on the planet.
Minnow is a name applied to about 300 species of freshwater fish of North and Central America. Read on to learn more.