Final answer:
Seagulls face the osmotic challenge of drinking seawater with high salt concentration, which is overcome by specialized osmoregulatory mechanisms that allow them to excrete excess salts and retain water.
Step-by-step explanation:
Seagulls face significant osmotic challenges when drinking seawater that has an osmolarity of 1000 mosm, which is much higher than their body fluids' normal osmolarity of 370 mosm. The main challenge is to expel the excess salt without losing too much water. Osmotic pressure causes water to move from an area of lower solute concentration (their body fluids) to one of higher solite concentration (the seawater). To cope with this, seagulls have evolved specialized osmoregulatory mechanisms. Unlike humans at sea who would become severely dehydrated from drinking saline water because of our inability to excrete the excess salt without losing too much water, seagulls can excrete salts through specialized glands while retaining water.
This osmoregulation in seagulls is similar to what is observed in marine fish, which also drink seawater and excrete excess salts through their gills. These marine animals have evolved to maintain water and electrolyte balance despite living in hypertonic environments. These adaptations are critical for their survival in marine habitats. It's worth noting that such adaptations are essential for marine organisms to live in environments that are seemingly inhospitable due to high salt concentrations.