16. Which ion serves as the primary signal responsible for neurotransmitter release at the axon terminal and has been widely used to reflect neural activity?
(A) Potassium efflux.
(B) Sodium efflux.
(C) Sodium influx.
(D) Calcium efflux.
(E) Calcium influx.

12. In animal physiology, when differentiating between roundworms, annelids, and snakes, which characteristics could you use? (A) Radial symmetry and dorsal nerve cord. (B) Radial symmetry and worm-like body shape. (C) Segmentation and dorsal nerve tube. (D) Segmentation and bilateral symmetry. (E) Pseudocoelom and ventral nerve cord.

13. Which of the following is not a result of sexual selection? (A) Sexual dimorphism. (B) Infanticide. (C) Male competition. (D) Altruism. (E) Female choice.

14. What are the sex(s) of the model organism nematode worm, Caenorhabditis elegans? (A) Male and female. (B) Male and hermaphrodites. (C) Female and hermaphrodites. (D) Only hermaphrodites. (E) Male and female and hermaphrodites.

15. Most aquatic animals primarily excrete nitrogenous wastes as: (A) Ammonia. (B) Urea. (C) Uric acid. (D) Creatinine. (E) Nitrogen.

17. What is the primary factor enabling the rapid conduction of action potentials in the giant axons of squids? (A) Myelination. (B) Low threshold. (C) Increased sodium channels. (D) Multiple axons. (E) Large diameter.

18. Which receptor directly mediates the transmission of nerve impulses at the neuromuscular junction? (A) Nicotinic receptor. (B) Muscarinic receptor. (C) α Adrenergic receptor. (D) β Adrenergic receptor. (E) Orexin receptor.

19. What are the two neurohormones primarily released by magnocellular neurosecretory cells at the posterior pituitary? (A) Thyroxine and insulin. (B) Vasopressin and oxytocin. (C) Cortisol and adrenaline. (D) Growth hormone and prolactin. (E) Follicle-stimulating hormone and Luteinizing hormone.

20. The Nobel Prize in Physiology or Medicine 2014 was awarded for the discovery of place and grid cells, which are responsible for: (A) Circadian rhythm. (B) Special navigation. (C) CAT T cell therapy. (D) Spinal cord development (E) Cardiac regeneration

21. Identify the incorrect statement regarding the complex interactions within the gut-brain axis: (A) Short-chain fatty acids produced by gut microbiota can influence brain chemistry and behavior. (B) The gut-brain axis communicates through the central nervous system and the body's hormonal responses but does not involve immune responses. (C) Dysbiosis in the gut microbiota is linked to neurological and psychiatric disorders, such as depression and anxiety. (D) Gut microbiota can influence the epigenetic regulation of genes in the central nervous system, impacting neural development and function. (E) The gut-brain axis involves bidirectional communication, where not only does the gut influence brain function, but the brain also significantly affects gut microbiota composition and function.

22. Which of the following statements about the effects of oxaliplatin on SW480 colon cancer cells, as observed in the DNA content histogram plots, is incorrect?  (A) An increase in the sub-G1 population after oxaliplatin treatment indicates a rise in apoptotic cells due to DNA fragmentation. (B) Oxaliplatin treatment leads to DNA damage in SW480 colon cancer cells. (C) The accumulation of cells in the G2/M phase after oxaliplatin treatment suggests cell cycle arrest at this phase. (D) Oxaliplatin treatment causes a majority of SW480 cells to pass through the G1 phase, indicating enhanced cell proliferation. (E) Cells with a 4N DNA content cannot be distinctly separated into G2 and M phases due to their similar DNA content.