General features of animals

The following features characterize members of the Kingdom Animalia:

(e) Diverse in Form
Almost all animals (99%) are invertebrates, which lack a backbone. Of the estimated 10 million living animal species, only 42,500 have a backbone and are referred to as vertebrates. Animals are very diverse in form, ranging in size from organisms too small to see with the unaided eye to enormous whales and giant squids.