In balancing selection, two or more alleles are kept in balance, and therefore are maintained in a population over the course of many generations. Which of the following example can support balancing natural selection?

A- Sickle cell allele kept in balance because heterozygotes have greater chance of survival if infected by the malarial parasite, compared with normal homozygotes

B. One morph has selective advantage over another morph

C. One homozygote has greater chance of survival than other genotype results in purity of population

D. many species of invertebrates exist as different colored forms, identical in all respects except color. Visually searching predators often develop a search image for one color form, usually the commoner

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#Question id: 12051

#Unit 7. System Physiology – Animal

Migrating motility complexes (MMC) occur about every 90 min between meals and are thought to be stimulated by the gastrointestinal hormone, motilin. An absence of MMCs causes an increase in which of the following?

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#Question id: 12050

#Unit 7. System Physiology – Animal

A clinical experiment is conducted in which one group of subjects is given 50 g of glucose intravenously and another group is given 50 g of glucose orally. Which of the following factors can explain why the oral glucose load is cleared from the blood at a faster rate compared to the intravenous glucose load? (CCK, cholecystokinin; GLIP, glucose-dependent insulinotropic peptide; VIP, vasoactive intestinal peptide)

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#Question id: 12049

#Unit 7. System Physiology – Animal

Which of the following hormones is released by the presence of fat and protein in the small intestine and has a major effect to decrease gastric emptying?

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#Question id: 12048

#Unit 7. System Physiology – Animal

A 10-year-old boy consumes a cheeseburger, fries, and chocolate shake. The meal stimulates the release of several gastrointestinal hormones. The presence of fat, carbohydrate, or protein in the duodenum stimulates the release of which of the following hormones from the duodenal mucosa?

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#Question id: 12047

#Unit 7. System Physiology – Animal

Biopsies are taken from the antral and duodenal mucosa of a 65-year-old woman. Which of the following hormones can be found in tissue homogenates from both locations?

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#Question id: 12046

#Unit 7. System Physiology – Animal

Which of the following ions has the highest concentration in saliva under basal conditions?