Amphibians, Reptiles, Birds

The few data that are.available have been assembled by Voronkov, Zelchan, and Lukevits (4a). In some cases it is not possible to decide whether the reported amount of silica is greater than could have been present as Si(OH)4 in solution in the body j fluids. Thus if the organism consisted of 50% water and 10% ash and the water were saturated with amorphous silica, the silica in the ash would be 0.05%. Generally, the. silica is no lower than 0.1-0.2% based on ash. Skin, feathers, intestines, etc., which. can be exposed to contact with materials from outside, are all higher in silica. For example, feathers may contain up to 77% silica in the ash, strongly suggesting the possibility of physical adsorption of colloidal silica or silicates. Also, earlier data - may indicate a falsely high silica level because of interference by phosphorus in the. silicomolybdate test. 

It has often been assumed that in higher life forms, that is, animals, the element silicon is not essential. However, Holzapfel (173, 174) showed that silica is present in trace amounts in most animals and thus might have some definite function. 

Animals invariably take in a certain amount of silica in water but, unlike plants, can also excrete silica in solution so that no accumulation in the body need occur. Taken orally silica is almost certainly innocuous. Rabbits have been fed 2 grams of silica gel per day for 30 weeks with no ill eflects (175). Magnesium silicate, which is easily attacked by acid, liberating silica, is used in internal medicine. 

Whether or not the ingestion of silica gel could be beneficial under some circumstances is a matter of debate. Tabasheer, the silica gel found inside bamboo (94), was once believed to be of value in treating asthma and tuberculosis (98), and it is conceivable that there might have been some practical basis for the treatment, as has been the case with other primitive medications. 

In Europe around 1920 there was some interest in silicic acid as a therapeutic agent for tuberculosis. For example, Gonnermann (176) pointed out that the herbs 

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Phylum Chordata Tunicates, sharks, bony fishes, amphibians, reptiles, birds, mammals... 

This form of luminescence occurs sporadically in a wide range of natural organisms, such as protists (bacteria, fungi), animals, marine invertebrates and fish. It even exists naturally, albeit rarely, in plants or in amphibians, reptiles, birds, or mammals. 

Terrestrial tetrapods adjust by avoidance of evaporative stress, reduction of evaporative and urinary water losses, and temporary toleration of hyperthermia or hypernatremia. Antidiuretic hormone (ADH) from the neurapophysis is very important in enhancing uptake of water through the skin (amphibians), reduction in glomerular filtration (amphibians, reptiles, birds), and increase in tubular reabsorption of water (mammals). 

Many fundamental concepts in modem biology have been established through studies on aquatic organisms. Fish are of special interest to research workers, because some of their metabolic features characterized early vertebrates. Fish have also evolved numerous adaptations, which have permitted them not only to survive but also to thrive in recent times. The range of structural and functional adaptations and metabolic flexibility, combined with individual specializations, has resulted in an immense diversity of fish - more than 20 000 species - which greatly exceeds that of amphibians, reptiles, birds and mammals. As the final link in many food chains, fish can be reliable indicators of the condition of complex ecosystems. Studies on fish provide an understanding of the pathways of metabolic substances and of energy transformations in bodies... 

Hydrogen in the sun and in the waters of our blue planet, together with nuclear in the sun and in the soil under our feet provided conditions that were appropriate for the development of life on the Earth 4 billion years ago. Humans arrived after a long chain of evolution of living beings that included simple and multiple cell organisms, fish, insects, amphibians, reptiles, birds, mammals... with whom we still share an important part of our genes. 

Calcium is essential to all living things. Calcium compounds are a vital component of the skeletons and bones of mammals, amphibians, reptiles, birds, fish, and other land and marine animals. The most abundant metal in the human body, calcium makes up the bones and serves other functions in the body s metabolic system. These functions include keeping cells joined together, aiding in muscle contraction and conduction of nerve impulses, helping blood clot, and controlling cell division. 

Figure 2. Numbers of Papers Dealing with Fish, Amphibians, Reptiles, Birds and Marmnals in the Journal of Chemical Ecology from its Inception in I97S to 2003.

Tetrapoda In some classifications, a superclass of jawed chordates ( Gnathostom-ata) comprising all vertebrate animals with four limbs, l.e. the amphibians, reptiles, birds, and mammals. The skeleton of the limbs of all tetrapods is based on the same five-digit pattern (see pentadactyl umb). 

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