Read Comparative Excretion

Fish intake relates to gland-size adaptation. The graph shows a negative relationship between percent fish in diet and relative salt-gland depression size: species eating more fish tend to have smaller salt-gland depressions, whereas those eating more marine invertebrates have larger ones. This supports B. The outlying Adelie penguin is consistent with a recent shift from a fish-rich to a krill-rich diet, so gland morphology may lag behind diet, supporting D.

Nephridia, Malpighian tubules and related structures. Earthworms excrete through nephridia, not antennal (green) glands; those glands are characteristic of crustaceans. The other listed pairings are correct.

Trace the excretory route before naming the organ: earthworm coelomic fluid enters a metanephridium through its nephrostome and exits via a nephridiopore. Aquatic vertebrates instead adjust kidney and gill transport to their salinity; seawater teleosts drink seawater and actively excrete excess salts.

First separate the water and ion problems. In the stated aglomerular-toadfish model, moving to much more dilute seawater requires tubular solute excretion and stronger branchial and intestinal solute uptake. Therefore choose B and D. Do not reverse the direction of water flow or predict a rise in plasma osmotic pressure.