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The Teeth of Herbivores
Herbivorous animals are adapted to eat vegetation. The sheep has no front teeth on its top jaw. Instead it has a hard pad of gum. The front teeth in its bottom jaw are small and sharp.
The sheep eats grass which is easy to pull out of the ground. Grass must be chewed well, however, to break it down into small pieces before it is swallowed.
The sheep’s back teeth are very large and have broad surfaces. The ridges of the bottom teeth fit together. The sheep moves its jaw from side to side. The grass is broken up between these large molars.
Herbivorous birds do not have teeth to grind up the vegetation they eat. Teeth would make their skulls too heavy and make flight difficult. Instead, a part of their digestive system, called the crop, contains stones which grind up the plant material they eat.
Some herbivores are called ruminants. The cow and the giraffe are ruminants. These animals have two stomachs. During the day they chew their food in the same way as sheep. When a ruminant swallows, the food goes into the first stomach, called the rumen. In the evening the animal brings a mouthful of food back into its mouth from its first stomach. This is called regurgitating the food. The food is chewed well again before it is swallowed into the second stomach. This second chewing is called chewing the cud.
These mammals have two pairs of large teeth at the front of their mouths. One pair of teeth is found in the top jaw and the other pair in the bottom jaw. These gnawing teeth allow animals, such as the rat and squirrel, to bite through hard seeds.
All herbivores need to chew their food well. The locust or cricket has many complicated parts to its mouth. Two of these parts are called mandibles. The mandibles are made of a very hard substance called chitin. Every blade of grass the insect eats is passed between the mandibles. The surface of the mandibles is very similar to the surface of the back teeth of the sheep. The grass is crushed between the two mandibles as they come together.
The Roman, or edible snail can be as much as 25 cm long with a mass of 250 grammes. Snails have a long tongue called a radula. The radula is covered with many rows of teeth. There are 20000 teeth altogether. These teeth have flattened surfaces and the snail uses the radula to scrape off small pieces of food which are then sucked into its body.
The earthworm eats soil which contains a lot of vegetable material. It has no teeth to grind this vegetation but a part of its digestive is adapted to do this. There is a small pouch, called the crop, which contains many small, sharp stones. When the food reaches the crop it is cut up into much smaller pieces by these sharp stones.
Many animals which live in water feed on the small microscopic animals and plants in the plankton. Mussels create a current of water through their bodies, using muscles. As the water moves through, special hair-like structures sieve out the plankton. This is called filter feeding.
The flamingo is also a filter feeder. It puts its head upside down into the water and moves its head from side to side. The flamingo’s tongue is very large and it is moved to the back of the mouth to suck in water containing the food. The tongue is then pushed forward to push out the water but the food is trapped in the fine hairs around the beak. The trapped food is then swallowed. The flamingo’s diet includes small shrimps which are pink. This pink colour moves into the flamingo’s feathers, giving them the same pink colour.
Some animals feed only on liquids and therefore need to suck their food. The female mosquito feeds on blood. The mouthparts are very long and thin and able to be pushed into the skin of the victim without being felt. The butterfly drinks nectar from flowers. It has a very long mouthpart called a proboscis. This tube is coiled under its head when it is flying and can be extended when it feeds.
Humming birds are small birds with long beaks and a long tongue. They also drink the nectar from flowers. Aphids put their thin but strong, pointed mouthparts into the stems of plants to suck the plants’ food. The housefly has a proboscis shaped like the end of a vacuum cleaner. It uses it to suck the juices from the food which it walks over.