Claytonia virginica is a woodland spring herb with flowers that vary from white, to pale pink, to bright pink. Slugs prefer to eat pink-flowering over white-flowering plants (due to chemical differences between the two), and plants experiencing severe herbivory are more likely to die. The bees that pollinate this plant also prefer pink to white flowers, so that Claytonia with pink flowers have greater relative fruit set than Claytonia with white flowers. A researcher observes that the percentage of different flower colors remains stable in the study population from year to year. Given no other information, if the researcher removes all slugs from the study population, what do you expect to happen to the distribution of flower colors in the population over time?

TLS Online TPP Program

#Question id: 34163

#Unit 7. System Physiology – Animal

Which of the following represents the correct sequential pathway for aldosterone synthesis from cholesterol, based on the enzyme-catalyzed steps?

TLS Online TPP Program

#Question id: 34164

#Unit 7. System Physiology – Animal

A newborn is diagnosed with 21β-hydroxylase deficiency. Which of the following downstream consequences is most likely due to impaired glucocorticoid production during fetal life?

TLS Online TPP Program

#Question id: 34165

#Unit 7. System Physiology – Animal

Following statements are regarding thyroid hormone biosynthesis?

I. The basolateral membranes of thyrocytes facing the capillaries contain a antiporter that transports two Na⁺ ions and one I^– ion into the cell with each cycle, against the electrochemical gradient for I^–.

II. Na⁺/I^– symporter (NIS) is capable of producing intracellular I^– concentrations that are 20–40 times as great as the concentration in plasma.

III. TSH induces both NIS expression and the retention of NIS in the basolateral membrane, where it can mediate sustained iodide uptake.

TLS Online TPP Program

#Question id: 34166

#Unit 7. System Physiology – Animal

I. Adrenocortical secretion is controlled primarily by ACTH, from the anterior pituitary, but mineralocorticoid secretion is also subject to independent control by circulating factors.

II. Adrenal medullary hormones work mostly to prepare the body for emergencies, the so-called “fight-or-flight” responses.

III. All three cortical zones secrete corticosterone, but the active enzymatic mechanism for aldosterone biosynthesis is not limited to the zona glomerulosa.

IV. An important function of the zona glomerulosa, in addition to aldosterone synthesis, is the formation of new cortical cells.

TLS Online TPP Program

#Question id: 34167

#Unit 7. System Physiology – Animal

I. The adrenal medulla does not regenerate, but when the inner two zones of the cortex are removed, a new ZF and ZR regenerate from glomerular cells attached to the capsule.

II. Immediately after hypophysectomy, the ZF and ZR begin to atrophy, whereas the ZG is unchanged because of the action of angiotensin II on this zone. 

III. The ability to secrete aldosterone and conserve Na+ is normal for some time after hypophysectomy, but in longstanding hypopituitarism, aldosterone deficiency may develop, apparently because of the absence of a pituitary factor that maintains the responsiveness of the zona glomerulosa. 

TLS Online TPP Program

#Question id: 34168

#Unit 7. System Physiology – Animal

Angiotensin II stimulates aldosterone production in the zona glomerulosa by binding to AT1 receptors. Which of the following best describes the intracellular signaling pathway and its role in aldosterone biosynthesis?