Lab 8 Vertebrate homologies:Layout 1.qxd

Incisors: Well developed chisel-shaped teeth with a
cutting edge. These teeth are primarily used for obtaining
food.
Canines: Conical shaped teeth that are adapted for
stabbing, holding, or tearing.
Premolars: Teeth that contains several points (cusps)
for tearing and slicing
Molars: Largest of the teeth that may contain points in
carnivores. In herbivores they are usually flat and
adapted for grinding cellulose in plant cell walls. Both
the premolars and molars are used primarily for chewing.
The dental formula is a shorhand notation expressing
the number of each kind of tooth in the jaws. Teeth in
the upper jaw are noted above the line; those in the lower
jaw are noted below the line. Using the human as an
example, the dental formula would be written as such:
incisors(4)-canine(2)-premolars(4)-molars(6) in upper jaw = 16
incisors(4)-canine(2)-premolars(4)-molars(6) in lower jaw = 16
Total number of teeth = 32
The basic design of teeth and jaws in mammals is similar. However, there are adaptations based
on the primary food source of the mammals.
Omnivores, such as pigs and bears and humans, may eat anything, including vegetation and meat.
The molars and premolars are adapted for both grinding and crushing.
Carnivores, such as cats, dogs, and wolves are meat eaters. They have teeth that are welldifferentiated
and adapted for securing and eating flesh. The canines are long and sharply-pointed
for seizing and tearing prey. The premolars and molars are flattened laterally and have sharp edges
for cutting. The skull is also adapted for the attachment of strong muscles required for meat eating.
Insectivores, such as moles, some species of bats, shrews, and hedgehogs do not have well
differentiated teeth. All of the teeth are short and have sharp points (cusps).
Herbivores, such as cows and deer are plant eaters. The incisors are flat and sharp for cutting off
vegetation or, in the case of browsers, the upper incisors may be absent. The canine teeth may also
be absent in herbivores, leaving a space between the incisors and the cheek teeth (premolars and
molars). The cheek teeth are broad and flat to provide a large surface area for grinding and mashing
8-2