Biology Organismal Biology & Physiology Flashcards

A plant in a desert environment has thick, waxy cuticles and sunken stomata. These adaptations primarily help the plant to:

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.

The sinoatrial (SA) node is often called the pacemaker of the heart because it:

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.

Which digestive enzyme is secreted by the pancreas and is responsible for breaking down starch in the small intestine?

Answer: Pancreatic amylase

Pancreatic amylase is released into the duodenum and hydrolyzes starch into maltose and shorter oligosaccharides.

In vertebrates, the myelin sheath around axons is produced by which cells in the peripheral nervous system?

Answer: Schwann cells

Schwann cells wrap around peripheral nerve axons to form the myelin sheath, increasing the speed of action potential conduction.

Which event triggers ovulation in the human female menstrual cycle?

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.

Gas exchange in terrestrial insects occurs via a network of air-filled tubes called:

Answer: Tracheae

Insects use a tracheal system—branching chitinous tubes—to deliver oxygen directly to tissues, bypassing the circulatory system for gas transport.

Which photoreceptors in the human eye are responsible for color vision and function best in bright light?

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.