AMMONOTELISM
As body cells carry out metabolic activities, they consume oxygen and nutrients and produce waste products such as carbon dioxide, urea, and uric acid. Wastes must be eliminated from the body because they can be toxic to cells if they accumulate. The excretory system disposes of most of the wastes. The excretory system performs this function by removing wastes from the blood and excreting them into urine. There are various ways organisms eliminate metabolic waste products from their bodies. Different organisms have different excretory products and their elimination like ammonotelism, ureotelism, and uricotelism, depending on their habitat and physiology.
Ammonotelism is the process of excreting nitrogenous waste in the form of ammonia. It occurs mainly in aquatic animals like fishes, amphibian larvae, and protozoans. Since ammonia is highly toxic and soluble, ammonotelic animals require large amounts of water for excretion, making this process energy-efficient but water-dependent. Have we wondered how fishes or other organisms excrete their wastes as they are aquatic? Here we will discuss one of the forms of nitrogenous waste excretion.
What is Ammonotelism?
Ammonotelism is the process of excretion of nitrogenous waste in the form of ammonia. The organisms that excrete waste by ammonotelism are called ammonotelics. The excretion product, ammonia is highly toxic and produces ammonium hydroxide with water and is highly soluble in water. It must be eliminated from the body once it is formed.
Since ammonia can damage cells by alkaline reaction, excretion of ammonia needs a large quantity of water. In some invertebrates urea is hydrolyzed to carbon dioxide and ammonia. In fish and other amphibians, allenoate (salt or ester of allenoic acid) is turned into urea and glyoxylate.
Excretion and its Importance
Excretion is the process of eliminating unwanted substances from the body. It is done by the excretory system. Wastes are generated by metabolic activities done by the body. Wastes are ammonia, water, excess salt, uric acid, and carbon dioxide. Some of the wastes can harm the body if not removed. Excretion eliminates these wastes. Nitrogenous waste in the human body is urea. Extra nucleic acids and amino acids are broken by the liver. Urea is transported by the blood to the kidney. Kidney filters and waste is eliminated as urine. Major important functions of excretion are:
Excretion of wastes: By forming urine, the kidneys help excrete nitrogenous wastes from the body
Osmoregulation: It helps in the regulation of pressure in fluid by the release of excess water.
Regulation of pH: The kidneys excrete a variable amount of hydrogen ions into the urine and conserve bicarbonate ions, which are an important buffer of H+ in the blood. Both of these activities help regulate blood pH.
Modes of Excretion
There are five modes of excretion based on the product excreted.
Ammonotelism-ammonia(highly harmful) excretion
Uricotelism-uric acid excretion
Aminotelism-amino acid excretion
Ureotelism-urea excretion
Guanotelism-guanine excretion
Excretion Of Ammonia
When the organism's surrounding has a low ammonia level and the organism has a high ammonia level, then through passive diffusion (diffusion of molecules from a higher concentration region to a lower concentration region through the membrane) ammonia gets released into the surrounding.
This nitrogen excretion mechanism is not adoptable for animals that live in high ammonia water. Echinoderms, Platyhelminthes excrete ammonia by direct diffusion (through skin).
Aquatic fish excretes mostly through gills.
The excretion of ammonia needs the least energy.
Examples of Ammonotelism
All ammonotelics are aquatic animals.
Examples are
Larvae of amphibian
Fishes
Protozoans
Cephalopods
Platyhelminthes
Ammonotelism vs Other Modes
Mode of Excretion | Primary Waste Product | Toxicity | Water Requirement | Energy Requirement |
Ammonotelism | Ammonia | Very Toxic | Very high (needs continuous dilution) | Very low (no conversion needed) |
Ureotelism | Urea | Moderate | Moderate (less than ammonia) | Moderate |
Uricotelism | Uric acid | Low | Very low (excreted as paste/solid) | High (energy - intensive synthesis) |
Aminotelism | Moderate | High (diluted in water) | Very low (no conversion) | |
Guanotelism | Guanine | Very low | Negligible (excreted in solid form) | High |
Ammonotelism NEET MCQs
Q1. The most toxic nitrogenous waste excreted by many bony fishes, aquatic amphibians and aquatic insects is
CO2
Ammonia
Urea
Amino acids
Correct answer: 2) Ammonia
Explanation:
Ammonia is the most toxic excretory product.
Ammonia is extremely harmful to the body and is a consequence of protein metabolism. Fish and other aquatic species release ammonia straight into the water where it is diluted because it needs a lot of water to be safely expelled.
On the other hand, to save water and avoid toxicity terrestrial animals (including humans) transform ammonia into less harmful forms like urea or uric acid. Mammals can expel concentrated urea through urine, and it is less harmful than ammonia. Even less harmful uric acid is expelled as a paste to save water and is present in birds and reptiles.
Hence, the correct answer is option 2)Ammonia.
Q2. Assertion: Sharks are categorized as ammonotelic animals.
Reason: Sharks have the ability to retain significant amounts of ammonia in their blood.
Both the assertion and reason are true, and the reason is a correct explanation of the assertion.
Both the assertion and reason are true, but the reason is not a correct explanation of the assertion.
The assertion is true, but the reason is false.
Both the assertion and reason are false.
Correct answer: 4) Both the assertion and reason are false.
Explanation:
In this case, the assertion claims that sharks are categorized as ammonotelic animals. However, this assertion is false. Sharks are ureotelic animals, meaning they excrete urea as their primary nitrogenous waste product, not ammonia.
The reason given is that sharks have the ability to retain significant amounts of ammonia in their blood. This reason is also false. Sharks do not retain ammonia in their blood; instead, they convert ammonia into urea through their liver, which is then excreted.
Hence, the correct answer is Option (4) Both the assertion and reason are false.
Q3. Choose the incorrect statement
The process of excreting ammonia is Ammonotelism
Kidneys play any significant role in the removal of ammonia
Ammonia, as it is readily soluble, is generally excreted by diffusion across body surfaces or through gill surfaces (in fish) as ammonium ions
Many bony fishes, aquatic amphibians and aquatic insects are ammonotelic in nature
Correct answer: 2) Kidneys play any significant role in the removal of ammonia
Explanation:
Types of Animals Based on Excretory Wastes -
Ammonotelism:
The process of excreting ammonia is Ammonotelism.
Many bony fishes, aquatic amphibians and aquatic insects are ammonotelic in nature.
Ammonia, as it is readily soluble, is generally excreted by diffusion across body surfaces or through gill surfaces (in fish) as ammonium ions.
Kidneys do not play any significant role in its removal.
Hence, the correct option is Kidneys play significant role in the removal of ammonia
Also Read:
FAQs on Ammonotelism
Define ammonotelism and give examples.
Ammonotelism is a type of excretion in which ammonia is the primary nitrogenous waste product. Since ammonia is highly soluble and toxic, it must be excreted quickly and in diluted form. This type of excretion is mainly found in aquatic animals, where water is abundant for rapid removal of ammonia.
Ammonotelic animals include most bony fishes (teleosts), amphibians like frogs (in water), and aquatic invertebrates such as sponges, cnidarians, and crustaceans. These organisms live in aquatic environments where ammonia can be easily diffused out of the body into surrounding water.
What are the different modes of excretion?
Excretion refers to the process of eliminating nitrogenous waste products formed during metabolism. Different animals have evolved distinct modes of excretion depending on habitat and water availability. These mechanisms help maintain osmotic balance and nitrogen metabolism in organisms. The major types are:
Ammonotelism (ammonia excretion)
Ureotelism (urea excretion)
Uricotelism (uric acid excretion)
Aminotelism (amino acid excretion)
Guanotelism (guanine excretion).
Why is ammonia toxic in animals?
Ammonia is toxic because it can alter the pH of body fluids and disrupt cellular metabolism. High concentrations of ammonia can interfere with enzyme activity and the functioning of the nervous system, leading to convulsions or even death. Since it is highly reactive and cannot be stored safely inside the body, animals must eliminate it immediately.
Why do ammonotelic animals need more water?
Ammonotelic animals need more water because ammonia must be excreted in a very dilute form to prevent damage to tissues. To achieve this, large amounts of water are required to dissolve and flush out ammonia. This is why ammonotelism is common in aquatic animals, where water is available in abundance, but not in terrestrial animals where water is scarce.
Frequently Asked Questions (FAQs)
Humans do not produce ammonia as they are toxic and can cause damage to cells. ammonia occurs in the liver and kidney are converted to urea. urea is less toxic than ammonia and can be stored. it is less soluble and needs less water for excretion.
Ammonotelic- These are organisms that excrete nitrogenous waste in the form of ammonia. ammonia is highly toxic and soluble in water. It needs more water for excretion. ammonia must be excreted once it is formed.
Uricotelic- These are organisms that excrete nitrogenous waste in the form of uric acid.
Uric acid is insoluble and less toxic. It needs less water for excretion. uric acid can be stored in cells and body tissues.
Ammonia is toxic and it forms ammonium hydroxide with water. Because of this property ammonia excretion needs large amounts of water. ammonia is highly soluble in water. fishes are aquatic animals. They have plenty of water and can excrete ammonia by ammonotelism. so, fishes are ammonotelic.