Waste Products are the unwanted and toxic by-products that are removed to maintain homeostasis and protect the body from their toxicity
Context
1. Metabolic Waste Products
2. Types Of Animals Based based on excretory Products
1. Metabolic Waste Products
Metabolic wastes may be separated into gases, liquids, solids, and heat. Heat, though usually not classified as a waste product, should be classified as such because it is a by-product of metabolic activity and must be eliminated to avoid harmful elevation of body temperatures in warm-blooded animals. Gaseous wastes
Oxygen produced during photosynthetic reactions in green plants and certain bacteria may be considered to be a waste product, or at least a by-product, requiring removal. Carbon dioxide is produced by all animals and by green plants in darkness. Nitrogen gas is produced by denitrifying sulfur bacteria (Thiobacillus), and ammonia is excreted by decay-causing bacteria and by most invertebrate and vertebrate animals.
Liquid wastes
The sole liquid waste produced as a metabolic by-product by all animals and photosynthetic plants in darkness is water.
Solid wastes
Several important kinds of materials may be classified as solid wastes. Among them are nitrogenous wastes, by-products of protein and amino-acid metabolism by animals; nitrite and nitrate compounds produced by nitrifying bacteria; and sulfur and sulfates resulting from the metabolic activities of sulfur bacteria. Many other substances also enter into solid wastes to be disposed of by organisms. Iron compounds in an insoluble form are secreted by iron bacteria that have used soluble iron compounds. Various resins, fats, waxes, and complex organic chemicals are exuded from certain plants—as in the latex from rubber trees and milkweeds. Organic pigments from the breakdown of biological pigments, such as haemoglobin in vertebrates, become components of solid waste. Inorganic salts, including molecules and ions such as carbonates, bicarbonates, and phosphates resulting from life-sustaining chemical reactions, eventually may become solid waste products.
(i) Nitrogenous Waste Products:-
Eg. Xanthine, Guanine, Allantoin, Creatine, Hippuric acid, Uric acid, Urea, Ammonia.
(ii) Non-nitrogenous Waste Products:-
Oxalic acid, Lactic acid.
(iii) Excess Chemicals:-
Sodium, Calcium, Magnesium, Lead, Chlorine, Phosphorus, Iodine, Hormones, Vitamins, Wax etc.
2. Types Of Animals Based On Excretory products
(i) Ammonotellic Animals:-
Bony fishes, Aquatic Amphibians and Aquatic insects. It is readily soluble and is generally excreted by diffusion across body surfaces as Ammonium Ion. The kidney does not play any significant role in their removal. About 300-500 mL of water is required for the elimination of 1 gm of ammonia.
(ii) Uricotellic Animals:-
Excretes Urera. It mainly includes Mammals, Many terrestrial amphibians and marine fishes. In these organisms Ammonia produced by metabolism is converted into urea in the liver and released into the blood which is filtered and excreted out by the kidneys. Urea formation requires the expenditure of energy. It is formed in the liver nu the Ornithine cycle.
(iii Uricotellic Animals
Excretes uric acid. Shown in terrestrial animals as it is subsequent elimination requires a lesser amount of water,. It is less toxic as compared to ammonia. 10 mL of water is required for the elimination of 1gm of uric acid.
