How do plants show excretion


excretion, general. The excretion of substances that disturb the metabolic equilibrium.

1) at plants the excretion of salts and calcium oxalate, which occurs via certain excretory cells and tissues.

2) At Animals especially the excretion of solid, liquid or gaseous nitrogenous metabolic end products (Excreta). The excreta come mainly from the amino acid and nucleic acid metabolism, the primary waste product of which is ammonia (NH3) is. Although its direct E. is energetically very economical, many animals first convert ammonia into urea, uric acid or other nitrogen compounds because ammonia is so toxic. Which excretion product is formed depends primarily on the habitat and the water balance of the organism in question. According to the product excreted, three main forms of excretion can be distinguished, according to which the animals are classified as ammoniotelian or ammonotelian (Ammonia separator), as ureotelian (Urea separator) and as uricotelian (Uric acid separator, partly also purinotelian called).

Organisms living in water separate those that are very readily soluble in water ammonia straight from. Ammonia can easily pass through membranes and diffuses over the entire body surface, in fish over the gill epithelia, into the surrounding medium (mostly as NH4+). Land-living animals in dry habitats and animals whose embryos grow in waterproof eggs, shed uric acid out. This is sparingly soluble in water and can therefore be separated as a (mostly crystalline) precipitate and released as a kind of paste with the faeces. Uricotelian animals are e.g. lizards, snakes, tortoises, land snails, insects, birds. Some animals can switch from urea excretion to uric acid excretion when environmental conditions change (water scarcity). urea is the most important excretion product of many vertebrates (sharks and rays, amphibians, mammals). Since urea is readily soluble in water, a high osmotic pressure arises when it accumulates. Larger amounts of urea can therefore only be excreted if there is sufficient water and the ability to concentrate urine. Urea is produced in the liver of terrestrial vertebrates in the urea cycle from ammonia and carbon dioxide (CO2). It is transported from the liver to the kidney and excreted in the urine. In sharks in particular, some of the urea is not excreted but contributes to osmoregulation because it makes the shark's blood isotonic to seawater. Amphibians are usually ammonotelic as tadpoles and become ureotelian animals in the course of the metamorphosis, with exceptions here as well: The clawed frog, for example, also excretes ammonia after the metamorphosis and only switches to urea excretion if it has to live outside the water for several weeks.

Other excretions of nitrogen metabolism are, for example, amino acids (echinoderms, molluscs, crustaceans), guanine (especially in arachnids), trimethylamine oxide in marine Teleostei (its bacterial decomposition product trimethylamine causes the characteristic smell of dead sea fish) and creatinine, which is contained in the urine of vertebrates small amount occurs. (Excretion organs, excretion storage)