12.3.6 Egestion

Question 1

Egestion

Answer 1

• Egestion is the process by which undigested materials such as cellulose are expelled from the body.
• Many intestinal flora reside in the large intestine. Some intestinal flora are mutualistic symbionts. Mutualistic symbionts derive benefits from their host, and bring benefits to their host.
• Variations in digestive systems allow different organisms to digest specialized diets.

Question 2

large intestine

Answer 2

• The various fluids involved in digestion contain large amounts of water that are reabsorbed into the body. The
  large intestine, or colon, functions in the reabsorption of
  water present in digested materials. As undigested materials move through the large intestine, water is absorbed and wastes take on a solid form called feces.
• If less than normal amounts of water are absorbed, diarrhea may occur. In contrast, the absorption of too much water results in constipation.
• The large intestine serves as a home for many bacteria, which are referred to as intestinal flora.
• Many of the bacteria living in the large intestine are
  mutualistic symbionts. These bacteria feed on undigested materials in the large intestine and produce vitamins, such as vitamin K and several B vitamins, that are useful to the host as a byproduct. Escherichia coli. is one species of bacteria that inhabits the large intestine of humans.

Question 3

digestive system

Answer 3

• The digestive system of many herbivores is specially adapted for the digestion of cellulose. Many herbivores have specialized chambers within their digestive system that house microorganisms capable of digesting cellulose.
• Cows, for example, have a multicompart-mentalized stomach that allows for the digestion of cellulose. Food is partially digested in the rumenby bacteria that produce cellulase, the enzyme that breaks down cellulose. The food is then brought back to the mouth for further chewing and is swallowed again to a different stomach compartment.

Question 4

coprophages

Answer 4

• Coprophages are organisms that eat their own fecal material. For example, rabbits eat their fecal material, which contains undigested cellulose and nourishing by-products of bacterial fermentation. As the materials pass through the body again, they are further broken down, and nutrients are absorbed.

Question 5

Water is primarily reabsorbed from waste products in the

Answer 5

• large intestine

Question 6

Diarrhea can be caused by

i. failure to absorb water in the large intestine.
ii. absorption of too much water in the large intestine.
iii. secretion of excess water in the large intestine.

Answer 6

• i, iii

Question 7

Which of the following life processes is analogous to egestion?

Answer 7

• getting rid of wastes

Question 8

Most parasites do not kill their hosts for this would be maladaptive. However, cholera bacteria is different. How does the death of their host not result in the extinction of cholera bacteria?

Answer 8

• While cholera usually causes death by dehydration from excessive diarrhea, this process serves to further disperse the organism in the untreated water supplies of affected communities

Question 9

Cows are able to digest grass because of the enzyme cellulase, what is the source of that enzyme?

Answer 9

• Bacteria in their gut.

Question 10

Egestion is the process by which

Answer 10

• undigested materials are expelled from the body.

Question 11

The normal flora of the intestines are

Answer 11

• microorganisms.

- symbionts.

Question 12

Egestion does not include:

Answer 12

• release of carbon dioxide.

Question 13

Which phrase accurately describes beneficial intestinal flora such as E. coli ?

Answer 13

• mutualistic symbionts