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As you have probably noticed, we are different to cows. Its not just the way we look, but also what we eat, and because of the different dietary requirements, our digestive systems are different.

A herbivores diet is plant matter. Plant cells have a large amount of cellulose in them.

The problem is, cellulose is too large a molecule to be absorbed straight away, plus these animals cant digest cellulose on their own.

So how can they digest plant matter than?

In order to digest cellulose, herbivores need a specific enzyme called Cellulase.

Fungi, protozoan and bacteria can produce this enzyme.

Herbivores such as cows, koalas and kangaroos have a symbiotic partnership with these organisms. This type of relationship is called a mutualism relationship.

In fact baby Koalas actually eat their mothers faeces to obtain the useful bacteria.

These bacteria live in the intestine of animal. They get shelter and food, and in return they breakdown cellulose into usable nutrients for the host.

Similar to humans, some bacteria in the gut provides the animal with Vitamins.

Since the gut has very little oxygen, most of the bacteria action is anaerobic (doesn't require oxygen). Anaerobic respiration in bacteria leads to fermentation.

As such, the area this occurs is referred to as the ‘fermentation chamber’.

We can break up herbivore mammals into two groups, Hindgut and foregut fermenters.

The first thing you notice is their skull. The shape of their teeth is very different to omnivores or carnivores.

Herbivores have large, dull and flat teeth. This allows herbivores to chew, grind and break down complex plant matter.

Hindgut fermenters.

Hindgut fermentation occurs in the caecum. The caecum is inbetween the small intestine and large intestine (diagram to the right).

This method of digestion is not very effective. Products of their digestion are not completely absorbed.

Horses are hindgut fermenters. Their faeces contain large amounts of undigested plant matter.

To over come this possums and rabbits produce two types of faeces. One is produced by the Ceacum and then re ingested, so it can go through the intestine again.

Foregut fermenters.

Foregut fermenters have their fermentation chamber is located before the stomach. This is called a Rumen.

The food regurgitated, chewed again and then sent back to the stomach. This fermentation method is more efficient as the properly digested food is sent across the whole small intestine.

Kangaroos and Wallabies are foregut fermenters (diagram to the left).

1. List 2 differences between the human digestive system and a horses digestive system?

2. Explain where you would find the Ceacum

3. Explain where you would find the rumen

4. What is the advantage and disadvantage of a Ceacum compared to a Rumen.

5. Cellulose is a complex molecule and it is difficult to breakdown. How do animals break cellulose down?

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