Forms of life

When considering how the evolution of life could have come about, the seeding of terrestrial life by extraterrestrial bacterial spores traveling through space (panspermia) deserves mention. Much is said about the possibility of some form of life on other planets, including Mars or more distant celestial bodies. Is it possible for some remnants of bacterial life, enclosed in a protective coat of rock dust, to have traveled enormous distances, staying dormant at the extremely low temperature of space and even surviving deadly radiation The spore may be neither alive nor completely dead, and even after billions of years it could have an infinitesimal chance to reach a planet where liquid water could restart its life. Is this science fiction or a real possibility We don t know. Around the turn of the twentieth century Svante Arrhenius (Nobel Prize in chemistry 1903) developed this theory in more detail. There was much recent excitement about claimed fossil bacterial remains in a Martian meteorite recovered from Antarctica (not since... 

One of the principal substances obtained from archaea (one of the oldest forms of life on earth) is denved from a 40 carbon diol Given the fact that this diol is optically active is it com pound A or is it compound... 

Of all the monosaccharides d (+) glucose is the best known most important and most abundant Its formation from carbon dioxide water and sunlight is the central theme of photosynthesis Carbohydrate formation by photosynthesis is estimated to be on the order of 10 tons per year a source of stored energy utilized directly or indi rectly by all higher forms of life on the planet Glucose was isolated from raisins m 1747 and by hydrolysis of starch m 1811 Its structure was determined in work culmi nating m 1900 by Emil Fischer... 

ATP IS the mam energy storing molecule for practically every form of life on earth We often speak of ATP as a high energy compound and its P—O bonds as high energy bonds This topic is discussed m more detail m Sections 28 4 and 28 5... 

Biosolid- The resides of wastewater treatment. Formerly called sewage sludge. Biosphere- Zone incorporating all forms of life on earth. The biosphere extends from deep in sediment below the ocean to several thousand meters elevation in high mountains. 

It is a remarkable contrast that, whereas Zn is biologically one of the most important metals and is apparently necessary to all forms of life,( Cd and Hg have no known beneficial biological role and are amongst the most toxic of elements. 

Another important relationship between the salts of the soil and corrosion has to do with biological activity. Since the growth of plants and microorganisms depends upon the proper inorganic mineral nutrients, the action of these forms of life varies with the mineral content of the soil. While many of the possible indirect effects, such as the role of various nitrogenous... 

Every form of life feels its surroundings in one way or another. In response to the feel of the surroundings, it behaves according to a pattern which tends to prolong its existence. 

Peptidases are found in all forms of life. There are about 612 peptidases in humans, plus an additional 385 proteins that are homologous to peptidases but either have no or different catalytic activity. In general, 2% of all genes in a genome encode peptidases. 

All forms of life—animal, plant and even baeterial—are suseeptible to infeetion by... 

Although it is toxic in large doses, selenium is an essential micronutrient in all known forms of life. It is a component of the unusual amino acids selenocys-teine and selenomethionine. In humans, selenium is a trace element nutrient. 

A full appreciation of composition of a given form of life. Note - this may not be very closely knowable. It is not to be found from DNA, RNA or protein content alone but has to be uncovered as a complete analysis of all chemicals. How far is this possible It has not been carried out for any organisms in a systematic way. To what extent are organisms of variable composition dependent on the environment ... 

These chemical substances accumulated in the hydrosphere, which thus became a dilute soup from which the first forms of life evolved spontaneously. 

The criteria for making the distinction should be verifiable across a wide range. The definition should include both forms of life which are already known and hypothetical pre-life forms. It should be logically self-consistent. 

The discovery of the deep sea hydrothermal systems, and the sulphur-metabolising bacteria which live in them, caused some researchers to look more closely at the element sulphur. It seemed obvious to consider a link between sulphur bacteria— primitive life forms—and the emergence of the simplest forms of life, de Duve, 1974 Nobel Prize winner for medicine, joined the ranks of the biogenesis researchers in the 1980s. 

The interpenetration of these phenomena, mediated by HGT, is also likely to be of great importance for evolution. According to the authors, the genetic code, which plays a key role in all forms of life, leads to the prediction that the first steps of the process of the emergence of life evolved in a Lamarckian manner, with vertical descent driven back by powerful early forms of HGT. 

We are getting ever closer to the goal of synthetic life, and when that is achieved we will see more clearly the kinds of molecular systems that were likely to have assembled in the prebiotic environment to produce the first forms of life. 

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