Genetic variation is the answer to ur question
Xerostomia (hypo functioning of salivary glands )
Inferior mesenteric artery
The part of the colon located distal to the left colic flexure is derived from the hindgut is supplied by the inferior mesenteric artery. The distal part (lower third of the rectum) is supplied by the internal iliac artery. The ileocolic artery supplying the cecum is a branch of the superior mesenteric artery.
B
The other problems are not as easily solved; whereas, data collection over long periods of time is possible and was already done in the past, eg temperature and weather patterns. Therefore, this is the easiest limitation to overcome.
Mitosis
Explanation ~ Mitosis creates two daughter cells each having the same number and kind of chromosomes as the parent nucleus