Excretory Structures Across Animal Groups — NEET Biology
📚 Practice ConceptA survey of animal kingdom presents a variety of excretory structures. In most of the invertebrates, these structures are simple tubular forms whereas vertebrates have complex tubular organs called kidneys. Some of these structures are mentioned here. Protonephridia or flame cells are the excretory structures in Platyhelminthes (Flatworms, e.g., Planaria), rotifers, some annelids and the cephalochordate – Amphioxus. Protonephridia are primarily concerned with ionic and fluid volume regulation, i.e., osmoregulation. Nephridia are the tubular excretory structures of earthworms and other annelids. Nephridia help to remove nitrogenous wastes and maintain a fluid and ionic balance. Malpighian tubules are the excretory structures of most of the insects including cockroaches. Malpighian tubules help in the removal of nitrogenous wastes and osmoregulation. Antennal glands or green glands perform the excretory function in crustaceans like prawns.
Consider the following statements : 1. Ammonia is the most toxic form of nitrogenous waste and requires a large amount of water for elimination. 2. Uric acid is the least toxic nitrogenous waste and is removed with maximum water loss. 3. Many bony fishes, aquatic amphibians, and aquatic insects are ammonotelic in nature. 4. Nephridia in annelids help in both nitrogenous waste removal and osmoregulation. 5. Malpighian tubules are the excretory structures of insects like cockroaches and aid in osmoregulation.
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