Chapter 27, Problem 1R

The koala is a leaf-eating animal. What can you infer about its digestive system?

Summary Introduction

To review:

The digestive system of koala, a leaf-eating animal.

Introduction:

Koala is a mammal which mainly survives on a diet of eucalyptus leaves, something that is extremely poisonous to many animals. Eucalyptus leaves are rich in fiber and have a very low nutritional level. Koalas have the tendency to rarely drink water as they absorb the required amount of water from the leaves. Koalas have a specialized digestive system adapted to their unique diet that enables the detoxification of poisonous chemicals present in the eucalyptus leaves.

Explanation of Solution

The Koala’s digestive system consists of the esophagus, stomach, caecum, small intestine, proximal colon, distal colon, rectum, and anus. Caecum is a specialized fiber-digesting organ present in Koalas. Though humans also possess this organ, Koalas have a caecum that is about 200 cm long. This highly voluminous caecum harbors millions of bacteria which facilitate the digestion of fiber into a form that can be easily absorbed. The gut microflora of Koala also aid in the digestion of toxic compounds present in eucalyptus leaves. Deterioration of these unique microbes in the gut has severe effects that essentially make them stop feeding as they would not be able to break down such poisonous compounds.

Conclusion

The extremely developed caecum of Koalas, harboring cellulose-degrading microorganisms, facilitates the survival of Koalas which live on a unique diet of eucalyptus leaves.