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Ammonotelism refers to the process of excretion of nitrogenous waste substances by certain organisms, in form of ammonia. Excretion refers to the process of removal of unwanted and harmful products from the body. The excretory system removes all the waste substances from our bodies, especially nitrogenous waste. The process of excretion is important for the body as it aids the removal of waste from the body along with excess vitamins, bile pigments, and salts. The five modes of excretion are Ammonotelism, Uricotelism, Aminotelism, Ureotelism, and Guanotelism.
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Key Terms: Excretion, Ammonotelism, Nitrogenous, Waste, Ammonia, Removal, and Excretory system
Introduction to Excretion
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Metabolic activities result in the formation of waste substances in the body of all animals. There is also a mechanism in all animals to get rid of such substances. Few waste substances can harm the body if they remain in the body for long periods. Some of these waste substances are urea, carbon dioxide, ammonia, uric acid, water, etc. Excess of water, sodium, and vitamins also need to be eliminated.
The excretory system removes waste substances from our bodies, especially nitrogenous waste. Our body produces Urea, which is the primary nitrogenous waste. The liver breaks down a surplus of nucleic acids and amino acids in the body. Urea is then transported to the kidney by blood. Blood filters and removes the waste through urine.
Also Read: Excretion Process
Importance to Excretion
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- Excretion aids the removal of nitrogenous waste from the body.
- It also aids the removal of excess salts, bile, and vitamins from the body.
- The process of excretion helps in maintaining Osmoregulation in the body by removing excess water or retaining it in case of shortage.
Importance of Excretion
Mode to Excretion
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In animals, there are five modes of excretion. These are:
- a) Ammonotelism: excretion of ammonia
- b) Uricotelism: excretion of uric acid
- c) Aminotelism: excretion of amino acids
- d) Ureotelism: excretion of urea
- e) Guanotelism: excretion of guanine
Also Read: Excretion Overview
Ammonotelism: Mode of Excretion
Ammonotelism refers to the process of excretion of nitrogenous waste substances by certain organisms, in form of ammonia. Ammonia can harm the cells by alkaline caustic action. Ammonia results in the formation of ammonium hydroxide as it is highly water-soluble. The process of ammonotelism requires water in a large amount. Allantoin and allantoic acid are formed during the oxidization of a portion of uric acid.
Allantoate is hydrolyzed into urea and glyoxylate, in fishes and other amphibians. Hydrolyzation of urea into ammonia and carbon dioxide occurs in a few marine invertebrates.
Excretion in Animals
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- Excretion means the process of removal of unwanted and harmful products from any animal body.
- Metabolic activities would result in the formation of waste substances in animal bodies.
- These waste substances could harm the body if they don’t get removed even after long periods. Some of those are urea, carbon dioxide, ammonia, uric acid, water, etc.
- There are various modes of excretion used by animals to excrete nitrogenous waste. Ammonotelism deals with the excretion of ammonia.
Sample Questions
Ques. What is Uricotelism? (3 marks)
Ans. Animals that remove nitrogenous waste as uric acid are uricotelic animals. The waste removed is in form of paste or pellets. This process is the least toxic and results in minimal water loss, however, it is costly. Uricotelic animals include insects, reptiles, and birds. Uric acid is not soluble in water.
Ques. Write a note on Micturition. (5 marks)
Ans. The process of discharge of urine from the urinary bladder is called Micturition. This excretion occurs in animals and humans through the excretory system. The process of formation and excretion of urine is aided by the kidney. Micturition reflex occurs when there is an increase in the urge to urinate.
The process of Micturition occurs in two phases, the storage phase and the voiding phase. The storage of urine in the urinary bladder is the storage phase. The process of urinating until the bladder is empty is the voiding phase. The process of Micturition can be affected by several factors or diseases such as urinary retention, detrusor instability, and spinal cord trauma.
Ques. What are Aminotelism and Guanotelism? (3 marks)
Ans. Aminotelism: Aminotelism is the characteristic of echinoderms to excrete amino acids.
Guanotelism: In spiders, birds, reptiles, and earthworms, ammonia gets converted into guanine. There is no requirement of water for Guanotelism as it is insoluble in water.
Ques. Write a note on Urine Formation. (4 marks)
Ans. The human body excretes waste in form of urine. The kidney plays an important role in process of formation and excretion of urine. Normal human urine consists of five per cent solid waste and ninety-five per cent of water. The process of production of urine takes place in the nephron. The process of urine formation consists of three steps: Glomerular filtration, Reabsorption, and Secretion.
Urinary system and Urine formation
Ques. Explain the function of Tubules. (3 marks)
Ans. Tubules play important role in the excretory process. Glomerulus filters the blood. The collecting duct reabsorbs the water from filtrate. Proximal convoluted tubules remove toxins and absorb nutrients, water, and ions. Distal convoluted tubule maintains pH and reabsorbs sodium ions. Descending loop of Henle concentrates the filtrate whereas ascending loop of Henle dilutes the filtrate.
Ques. What is Ureotelism? (3 marks)
Ans. Organisms, in which the metabolic waste product is urea, are called ureotelic. Some amphibians and mammals are ureotelic. In the liver, the ammonia is converted into urea and released into the blood. Then, urea is excreted from the body by the kidney. To maintain osmolarity, the matrix of the kidney retains some urea. Humans excrete urea through urine and so they are ureotelic.
Ques. Write a note on Human Excretory System. (5 marks)
Ans. Excretion is a basic process for the survival of organisms. Humans and animals need to get rid of the waste in their bodies. The food we eat gets converted into waste during metabolic activities. The removal of waste from the body occurs through the excretory system. The excretory organs in humans are kidneys, urethra, ureters, and urinary bladder. Kidneys are located on both sides of the backbone. Kidney includes Henle's lop, Capsule, and Nephrons. The ureter extends from the renal pelvis. The main function of the urinary bladder is to store urine. The urinary bladder is empty after Micturition. The urethra is a tube that aids the excretion of urine.
Human Excretory System
Ques. What are various disorders of the excretory system? (3 marks)
Ans. The disorders of the excretory system include:
- a) Renal Failure
- b) Uremia
- c) Oedema
- d) Hypertension
- e) Diabetes Insipidus
- f) Kidney stones or Renal Calculi
- g) Renal Tabular Acidosis
- h) Bright’s diseases or Nephritis
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