Read Excretion Beyond the Kidney
The kidney is central, but skin, lungs and liver also remove wastes; animal groups use distinctive excretory structures.
Other and Comparative Excretion is the central idea in this question pattern. Identify the condition in the stem before applying the method below.
Assign each organ its role
Lungs remove carbon dioxide and water; the liver eliminates pigments and cholesterol in bile; skin eliminates sweat and sebum; kidneys remove nitrogenous wastes and regulate water and ions. Sebum contains sterols, hydrocarbons and waxes.
Compare animal structures
Earthworms use nephridia, cockroaches use Malpighian tubules, and rotifers use protonephridia with flame cells. Antennal/green glands are associated with crustaceans, not earthworms.
OlympIQ exam lens
- ✓Lungs: CO₂ + water; liver: bile pigments/cholesterol.
- ✓Sebum: sterols, hydrocarbons, waxes.
- ✓Earthworm: nephridia; cockroach: Malpighian tubules; rotifer: flame cells.
Green glands are not an earthworm excretory organ.
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