Identify the roles played by human gut bacteria. identify the roles played by human gut bacteria. ulcers are caused by the acid-tolerant bacterium helicobacter pylori. the human appendix houses mutualistic bacteria that digest cellulose. human gut bacteria synthesize all essential vitamins required by humans.

The correct answer is option (A) ulcers are caused by the acid-tolerant bacterium Helicobacter pylori.

Gut refers to the parts of the alimentary canal especially the stomach and the intestines. The healthy microflora of the gut is largely responsible for the overall health of an individual. They are involved in the fermentation of certain dietary fibers , synthesis of vitamin B and K and other beneficial roles are played by the bacteria.

Apart from being beneficial, the gut flora like the Helicobacter pylori is involved in the formation of ulcers. It causes ulcers in the duodenum and stomach. It secretes urease and creates an alkaline environment optimal for its survival. It also increases the secretion of hormone gastrin involved in the stimulation of hydrochloric acid. This over production of the acid causes inflammation of the lining of the stomach and intestines causing ulcers.

Cellulose cannot be digested by humans and the undigested cellulose helps in smooth funtioning of the intestine and not all essential vitamins are synthesized by the gut flora. Thus, the role played by the gut bacteria is ulcers are caused by the acid-tolerant bacterium Helicobacter pylori.

relative dating involves things like higher layers are most recent than rocks lower in the sequence. this can be extended to the known sequence of fossils. rocks containing rabbit fossils are later than those containing dinosaur fossils.  

absolute dating methods mainly use radioactive elements that have known rates of decay and produce recognizable products. for example potassium 40 decays to produce argon. once a rock has solidified the argon is trapped. by measuring the argon and potassium0 you can get an accurate number for the age.  

some other methods are good for archaeological ages. dendrochronology involves recognizing the sequence of tree rings. the orientation of magnetized particles in baked clay can be used to date a fire.

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