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.
The feature uniting all chordates (all vertebrates and some invertebrates) is that at some stage in their lives, all have a flexible supporting rod, a notochord, that runs through the length of their bodies.ifferences in Physical Characteristics. Vertebrates have a skeletal structure with a spinal column or backbone. Invertebrates have no backbone, while vertebrates have a well-developed internal skeleton of cartilage and bone and a highly developed brain that is enclosed by a skull.