Questions and Answers
What are the major forms of nitrogenous wastes excreted by animals?
Uric acid is the most toxic form of nitrogenous waste.
False
What process involves the excretion of ammonia?
Ammonotelism
Aquatic amphibians are typically __________ in nature.
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Which animals are referred to as ureotelic?
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Which of the following structures are excretory in Platyhelminthes?
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Match the following excretory structures with the organisms:
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What is the function of nephridia in earthworms?
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Kidneys play a significant role in the removal of ammonia in fish.
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Study Notes
Excretory Products
- Animals produce ammonia, urea, uric acid, carbon dioxide, water, and various ions (Na+, K+, Cl–, phosphate, sulfate) through metabolic activities or excess ingestion.
- These substances need to be eliminated from the body to maintain homeostasis.
Nitrogenous Wastes
- Three major forms of nitrogenous wastes are ammonia (most toxic), urea (less toxic), and uric acid (least toxic).
- Ammonia requires large volumes of water for excretion; it is excreted mainly by aquatic organisms through diffusion and is not removed by kidneys.
- Urea is formed from ammonia in the liver, allowing mammals, terrestrial amphibians, and marine fishes to conserve water.
Excretion Mechanisms
- Ammonotelism refers to the excretion of ammonia primarily by aquatic organisms such as bony fishes and amphibians.
- Ureotelic animals convert ammonia to urea, which is filtered by kidneys.
- Uricotelic animals (e.g., reptiles, birds, land snails) excrete nitrogenous wastes as uric acid, minimizing water loss by forming pellets or paste.
Excretory Structures in the Animal Kingdom
- Invertebrates often have simple tubular excretory structures, while vertebrates possess complex kidneys.
- Protonephridia or flame cells, found in Platyhelminthes and some annelids, regulate ionic balance and osmoregulation.
- Nephridia, present in earthworms, eliminate nitrogenous wastes and maintain fluid balance.
- Malpighian tubules in insects aid in waste removal and osmoregulation.
- Antennal or green glands in crustaceans perform excretory functions.
Human Excretory System
- Comprised of paired kidneys, ureters, urinary bladder, and urethra.
- Kidneys are reddish-brown, bean-shaped organs positioned between the last thoracic and third lumbar vertebrae, within the abdominal cavity.
- Each human kidney measures approximately 10-12 cm in length and 5-7 cm in width.
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Description
This quiz covers Chapter 16 on excretory products and their elimination in humans and animals. Explore how organisms manage waste products like ammonia, urea, and uric acid, and understand their physiological implications. Test your knowledge of the human excretory system and its various functions.
