Mutation is the only evolutionary mechanism that does little to change allele frequencies.
Answer:
The bacterial flora in the intestines are essential to homeostasis in the body, they not only break down food so the nutrients can be absorbed, they produce vitamins like biotin and vitamin K and guard against harmful bacteria that enter the system. While your heart is a vital organ, the brain (and the nervous system that attaches to the brain) make up the most critical organ system in the human body. The digestive system ordinarily gets 20% to 25% of the oxygenated blood pumped out by the heart and the receptors in muscles provide the brain with information about body position and movement, the brain controls the contraction of skeletal muscle the nervous system regulates the speed at which food moves through the digestive tract.
