Herbivores and Carnivores By Claire J, Claire E, Robyn and Ian

Carnivores Teeth The top and bottom canines thrust past each other as the jaw is closed, allowing the dog to pierce the body of its prey The premolars and molars and molars have sharp edges and are known as carnassial teeth.

Chewing food Dogs don’t chew their food, they keep it in their mouth long enough to chop it into small pieces to be swallowed. As meat doesn’t contain starch, amylase doesn’t need to be secreted and no chemical digestion happens in the mouth. Dogs stomachs contain even more acids than humans so they can eat rotten food without harm

Digestion in dogs As in humans, pepsin in the stomach breaks down proteins Dogs food contains no cell walls so it is easy for proteases and lipases to digest their plasma membrane and cytoplasm

Herbivores Cows are adapted to feed on a diet of green plants. The food that a cow eats is made up of cells surrounded by cellulose cell walls. No mammal is able to make an enzyme to digest cellulose. The energy value in plant food is in the cellulose molecules themselves.

Cow teeth The cow has no canine teeth, just a gap called a Diastema. This enables the long flexible tongue to move grass around in the mouth so it can be thoroughly chewed from all angles. The chewing is done by premolars and molars. The molars have broad surfaces with ridges and cusps. The ridges on the upper jaw fit into the cusps of the lower jaw. Grass lying between these teeth is ground thoroughly as the cows jaws move from side to side while it chews. The cow does have incisors on it’s lower jaw, they are shaped like chisels and point forward. It uses these to tear off grass, along with using it’s tongue. Cows teeth grow continually as the roots of a cows teeth remain open, allowing blood to enter the teeth and supply the living cells with oxygen and nutrients.

Cow stomach Only the abomasum is the equivalent of the stomach of a human or dog. This structure has evolved because it helps the cows get nutrients from plant material

Chambers of the stomach Inside the largest chamber the rumen, there is a community of anaerobic micro organisms. They produce enzymes which break down cellulose to celloboise and glucose. Other enzymes convert these sugars to fatty acids releasing carbon dioxide and methane as they do so.

The carbon dioxide and methane go up the oesophagus and the fatty acids are absorbed through the walls of the rumen. Most tissues in cows are adapted to use fatty acids as their main respiratory substrate. Material from the rumen and reticulum pass back up the oesophagus into the mouth where they are chewed before being re swallowed.

Bacterial proteins are digested to amino acids in the abomasum and absorbed by the cow. Some of the amino acids make urea which is used so that an ‘internal nitrogen cycle’ takes place via the salivary glands, saliva, stomach, blood and liver. Many cattle feeds contain urea to maximise the production of proteins in the rumen.