CLEP Biology Organismal Biology & Physiology 3 — Questions and Answers
Question 1: A plant in a desert environment has thick, waxy cuticles and sunken stomata. These adaptations primarily help the plant to:
- Increase the rate of photosynthesis
- Reduce water loss through transpiration (Correct answer)
- Attract pollinators
- Increase nutrient absorption from soil
Correct answer: Reduce water loss through transpiration
Thick waxy cuticles and sunken stomata reduce the water potential gradient and wind exposure, minimizing transpirational water loss in arid conditions.
Question 2: The sinoatrial (SA) node is often called the pacemaker of the heart because it:
- Pumps blood into the aorta
- Generates spontaneous electrical impulses that set heart rate (Correct answer)
- Prevents backflow of blood between chambers
- Receives oxygenated blood from the lungs
Correct answer: Generates spontaneous electrical impulses that set heart rate
The SA node depolarizes spontaneously at a regular rhythm, initiating each heartbeat and determining the intrinsic heart rate.
Question 3: Which digestive enzyme is secreted by the pancreas and is responsible for breaking down starch in the small intestine?
- Pepsin
- Salivary amylase
- Pancreatic amylase (Correct answer)
- Lactase
Correct answer: Pancreatic amylase
Pancreatic amylase is released into the duodenum and hydrolyzes starch into maltose and shorter oligosaccharides.
Question 4: In vertebrates, the myelin sheath around axons is produced by which cells in the peripheral nervous system?
- Astrocytes
- Oligodendrocytes
- Schwann cells (Correct answer)
- Microglia
Correct answer: Schwann cells
Schwann cells wrap around peripheral nerve axons to form the myelin sheath, increasing the speed of action potential conduction.
Question 5: Which event triggers ovulation in the human female menstrual cycle?
- A sustained rise in progesterone
- A surge in luteinizing hormone (LH) (Correct answer)
- A sharp drop in estrogen
- A surge in follicle-stimulating hormone (FSH) only
Correct answer: A surge in luteinizing hormone (LH)
The mid-cycle LH surge triggers the release of a secondary oocyte from the dominant follicle, an event called ovulation.
Question 6: Gas exchange in terrestrial insects occurs via a network of air-filled tubes called:
- Lungs
- Book gills
- Tracheae (Correct answer)
- Spiracles alone
Correct answer: Tracheae
Insects use a tracheal system—branching chitinous tubes—to deliver oxygen directly to tissues, bypassing the circulatory system for gas transport.
Question 7: Which photoreceptors in the human eye are responsible for color vision and function best in bright light?
- Rods
- Cones (Correct answer)
- Bipolar cells
- Ganglion cells
Correct answer: Cones
Cones are concentrated in the fovea, contain three types of opsin sensitive to different wavelengths, and mediate color vision in photopic (bright) conditions.
CLEP Biology Organismal Biology & Physiology 3
A plant in a desert environment has thick, waxy cuticles and sunken stomata.
These adaptations primarily help the plant to: