CLEP Biology Organismal Biology & Physiology 4

Question 1

Which hormone, produced by the thyroid gland, lowers blood calcium levels by inhibiting osteoclast activity?

Accepted Answer

Calcitonin

Answer

Calcitonin is secreted when blood calcium is high and reduces calcium levels by inhibiting bone resorption by osteoclasts.

Question 2

In a CAM plant such as a cactus, when are the stomata open to take in CO₂?

Accepted Answer

At night only

Answer

CAM plants open stomata at night to fix CO₂ into organic acids, storing it for daytime photosynthesis with stomata closed to reduce water loss.

Question 3

The countercurrent exchange mechanism in fish gills maximizes oxygen uptake because:

Accepted Answer

Blood and water flow in opposite directions, maintaining a diffusion gradient along the entire gill

Answer

Countercurrent flow keeps blood encountering progressively more oxygenated water throughout the gill, sustaining a concentration gradient for diffusion along the entire length.

Question 4

Which part of the brain is primarily responsible for maintaining balance and coordinating muscle movements?

Accepted Answer

Cerebellum

Answer

The cerebellum integrates sensory information from the vestibular system and proprioceptors to fine-tune motor commands and maintain equilibrium.

Question 5

Aldosterone, secreted by the adrenal cortex, primarily acts on the kidney to:

Accepted Answer

Increase sodium reabsorption in the distal tubule, driving water retention

Answer

Aldosterone upregulates sodium-potassium pumps and channels in the distal convoluted tubule, causing Na⁺ retention and K⁺ excretion, which raises blood volume and pressure.

CLEP Practice Test

CLEP Practice Test

CLEP Biology Organismal Biology & Physiology 4