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From Molecules to the First Cell
The prebiotic conditions on the earth in all probability were volcanic eruptions, lightning and heavy rains. There was no trace of free oxygen or an ozone layer in the atmosphere to absorb ultraviolet radiations from the sun. It is assumed that organic molecules would have originated in such climatic conditions. This is described as their abiotic origin. Laboratory experiments from 1953 onwards prove that organic molecules like amino acids, proteins, nucleotides, nucleic acids, lipids and ATP can be formed in similar conditions on the earth. Stan1r.y Miller's experiment described below is one such experiment (Fig. shown below). It is possible that such organic molecules similar to those synthesised in Miller's experiment would have got accumulated at several places in high concentration, giving rise to a kind of liquid soup.
Scientists have three different speculatiohs about the composition of a protobiont. Some consider it'as an aggregate of electrically charged molecules with water around them acting as a boundary and this is called as coacervate model (Fig. shown below). This model was proposed by Alexander Oparin. Sidney Fox proposed another model for protobiont formation called protenoid microsphere model. According to this model when water free mixtures of amino acids are heated at high temperature, they pol.yinerise to form protein-like molecules, called proteinoids. These can persist only if cooled quickly. According to a third model called as the lipid bilayer model of Richard Goldacre, an abiotically synthesised phospholipid bilayer was formed around a central space containing organic molecules. All such models are without any experimental or theoretical evidence. However, the supporters of each model try to explain how some life-processes like osmosis and budding, can be camed out by such protobionts.
Phylum platyhelminthes (13,000 species Flatworm) The body is flattened. Gastrovascular cavity is branched, dense bodies with many cell layers, mouth but no anus. Hermaphrodite
For convenience, living things are placed into different groups. Taxonomic breakdown of living things comprises the following categories: Family, Class, Genus, Phylum, Order, K
State the term - Neuroanatomists Broadmann Neuroanatomists Broadmann used a combination of staining and microscopy to map the cytoarcitecture (cell structure\type) of human ce
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Eye complications are very common in patients with diabetes. In fact, diabetes related eye diseases may not produce symptoms for a very long time and hence, it remains undetected t
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Q Under which environments do echinoderms live? Echinoderms are marine animals and they live in salt water.
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How Genetic Predisposition causing the underweight? Mother's Health Status; Poor nutritional status of the girl child coupled with under nutrition during pregnancy results in L
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