Class interval should always be a whole number and yet in this case we have a decimal number. The solution to this problem is to round off to the nearest whole number. In this example, 2.8 gets rounded up to 3. So now our class width will be 3; meaning that we group the above data into groups of 3 as in the table below.
Skeletons come in a number of forms, each suited for a particular set of lifestyles and environments. Skeletons can be rigid, semirigid, or soft. They can also be external or internal. Vertebrates have internal skeletons, called bony skeletons, which consist mainly of calcified bone tissue. Most invertebrates, such as insects, spiders, and crustaceans, have outer skeletons called exoskeletons.
Most vertebrates have a spinal column made of bones called vertebrae (see SPINE). But some, such as the shark, do not have a bony spinal column. Sharks have vertebrae made of cartilage.Vertebrates are classified in the phylum chordata and make up the subphylum vertebrata.hose bones are called vertebrae so the animals are vertebrates. The animals that do not have backbones are called invertebrates. Some examples of vertebrates include human beings, cats, dogs, fish, elephants, and chickens.