Phys Eco Exam 1 Symbiosis, cellulose and fermentation #4

What is the coral-dinoflagellate nutritional symbiosis?

Dinoflagellates (zooxanthellae) provide carbohydrates to coral polyps and receive a nitrogen source in exchange.

What is the hydrothermal-vent worm nutritional symbiosis?

Sulfur-oxidizing bacteria use hydrogen sulfide carried by worm hemoglobin and produce organic compounds for the worms.

What are chemoheterotrophic nutritional symbionts?

Endosymbionts that perform digestion inside the GI tract of many animals.

What is the most abundant carbohydrate in the world?

Cellulose.

Why does cellulose digestion usually require endosymbiosis?

Microorganisms living in the GI tract are usually required to digest it.

How do endosymbionts digest cellulose?

Through anaerobic fermentation by bacteria and/or protozoa.

What does microbial fermentation produce from cellulose?

Volatile fatty acids (VFAs): short-chain 2-, 3-, or 4-carbon compounds that the animal can use for energy.

What else can digestive symbionts provide?

Important vitamins.

Can any invertebrates produce their own cellulase?

Yes. Some have endogenous cellulase; silverfish were the example.

How do most invertebrates digest cellulose?

Using gut microbes; examples include snails, bivalves, and shrimp.

How do termites digest cellulose?

Using bacteria and protozoa.

What additional function can termite bacteria perform?

Nitrogen fixation, which is useful because wood is low in nitrogen.

Do vertebrates possess endogenous cellulase?

No.

What is foregut fermentation?

Fermentation occurring in large compartments before the true stomach, as in ruminants.

What is hindgut fermentation?

Fermentation occurring in the cecum or large intestine of monogastric animals.