Is the gastro intestinal tract reduced?(pls see details)?

Question

what happens to the gastro intestinal (GI) tract of multi-cellular organisms when they feed on the most basic food source (i.e. amino acids, lipids, glucose etc)? theoretically, Is the length of the GI tract reduced? would the stomach and some other parts still be present through thousands of years? or would the organism evolve to something of lesser GI length? i mean, if the organism feeds on the most basic components, wouldn't the stomach and other parts be non-functional?

Answer 1

I see three central issues:

First, as Doc pointed out, there are non-funcitoning organs. In order for the GI tract to be "reduced," there would need to be an evolutionary pressure, i.e., an advantage to be gained by the loss of the orgen. Then, when a random mutation led to a being with a reduced or missing organ, that being would be "more fit," and therefore produce more offspring and pass along the new genotype and phenotype. In terms of your question, it's difficult to know or predict how reduction or loss of organs, even in your scenario, would impart such evolutionary pressure.

Second, think about the unique function of each organ. Digestion begins in the mouth, where simple carbs are broken down by enzymes and foods are mechanically disrupted.... in the stomach, this continues... absorption of nutirents occurs in the digestive tract, water is absorbed in the large intestine.... In the scenario you propose, would any of these functions become obsolute? Presumably, if you obtained all nutrients in a liquid, the stomach may not be needed for further breakdown, etc.

Finally, many of the organs have other functions besides the obvious. The stomach, for example, produces the hormone stomatostatin, which regulates the release of growth hormone, insulin, and other factors. The system is so finely tuned that changing the dietary intake may not obviate the need for the organ. As an analogy, if I gave you an electronic ear, connected directly to your brian, you would still want the inner ear to remain in order to have balance.

Answer 2

the appendix is non functional, and the occasional Meckel's diverticulum is not function and the gall bladder is not a necessity.