Doing a single exercise on vertebrate anatomy is quite difficult because the body plans of vertebrates are very diverse. Vertebrates include fish, birds, amphibians, reptiles, and mammals. When we look at all of these organisms, we can see that there are many differences between all of the groups. But, there are also a surprisingly high number of similarities as well.
The vertebrate forelimb, for instance, has the bones humerus, radius and ulna, carpals, metacarpals, and phalanges. The exceptions to this are the bony and cartilaginous fishes, which have many more bones that do not correspond to those listed. But, birds, mammals, amphibians, and reptiles have (or least had) those bones. But, they are all modified for very different uses.
One use for the vertebrate forelimb is swimming. Whales, otters, and penguins have forelimbs that are modified for swimming. The bones in whales are rather compact and do not move within the flipper. This provides a strong ‘paddle’ by which whales can control the direction of their swimming. Otters, however, have more versatile arms that allow for more movement. The metacarpals and phalanges are connected by skin that provides a ‘webbed’ appearance. Penguins are birds and their forelimbs were first adapted for flight, then to swimming. But, their bone arrangement is only slightly different from whales.
Other differences between vertebrate forelimbs can be seen in organisms such as horses, wolves, and deer, which are modified for running. Flight, of course, is a mode of movement which requires special adaptations. The forelimbs of bats and birds are quite different, though they are both suited for flying. |
2002 McGraw-Hill Higher Education