Chordates, members of the animal phylum Chordata, which includes all mammals, birds, amphibians, reptiles, and fish. There are about 45,000 species of chordates. They are classified in four subphyla, the largest of which contains the vertebrates. All chordates share three basic characteristics. The first characteristic is a single dorsal nerve cord, which in mammals takes the form of the brain and spinal cord. The second is a flexible rod of cells called a notochord, which in vertebrates takes the form of the backbone. The third is the presence of gill slits at some stage during the development of the animal. All chordates have bilateral symmetry.
If you've ever placed catnip near a cat, you will notice that the plant causes the cat to react in an extremely unusual way. It will roll around and kick its legs. What is it in catnip that causes cats to have this reaction? Find out in this article.
Dik-Dik is a slender dwarf antelope found in the dry bushlands of East Africa. It stands about 14 inches (36 cm) high at the shoulder and weighs 6 to 7 pounds (2.7 to 3.2 kg).