theories of origin of life class 12

All these closely resemble and look similar to a corresponding marsupial. The coaceravates started absorbing organic substances and became anaerobic heterotrophs. In plants also, thorns and tendrils of Bougainvillea and Cucurbita represent homology. This caused a massive explosion throwing out hydrogen atom and related nuclei which became organised to into galaxies. C. ... Navigate through all biology MCQs for your studies if you are a Class 11th or 12th student or pre-medical entrance preparation. Examples are forelimbs of some animals like whales, bats and cheetah have similar anatomical structure, such as humerus, radius, ulna, carpals, metacarpals and phalanges. Vestigial organs like homologous organs provide evidences for organic evolution. (b) Ernst Haeckel propounded The theory of recapitulation or Biogenetic law which states that an individual organism in its development (ontogeny) tends to repeat the stages passed through by its ancestors (phylogeny), i.e. This concept was held by early Greek philosophers like Thales, Anaximander, Xanophanes, Empedocles, Plato, Aristotle, etc. Image Courtesy : (ii) These molecules were like RNA, protein and polysaccharides. A four-stage hypothesis has been proposed: Miller and Urey recreated probable conditions of primitive earth in the laboratory. Not only is it far too complex to have developed spontaneously, there is a chicken-and-egg paradox: No proteins without DNA to code for them, but No reason for DNA without proteins to code for. (a) Rocks form sediments and a cross-section of earth’s crust indicates the arrangement of sediments one over the other during the long history of earth. Image Courtesy : Origin of First Cell forces from non-living molecules It is accepted by many scientists. (iv) Analysis of the meteorite also revealed the presence of similar compounds. Theory of Panspermia or Cosmozoic Theory or Spore broth Theory. This is also true for microbes against which antibiotics or drugs have been used. Few examples are mentioned in the table. Content Guidelines 2. past but not today. (b) UV rays from the sun broke up water molecule into hydrogen and oxygen and lighter hydrogen escaped. (v) Chemical evolution of life was more or less accepted. Other theories such as the theory of Spontaneous Generation are of historical importance only. 1. He then boiled the solution till the steam passed out through the tube. The origin of life on Earth is a highly curious thing. Shares. Copyright 10. (ii) The earth was supposed to have been formed about 4.5 billion years back in the solar system of the milkyway galaxy. The presence of gill clefts in all vertebrate embryos including human provides a strong evidence in support of organic evolution. Many theories have been put forward to explain the origin of life. Thus, he showed that the source of the micro-organisms for fermentation or putrefaction such as for milk, sugar and wine, etc., was the air and the organisms did not arise from the nutrient media. (ii) Comparative anatomy and morphological evidences show the similarities and He created the whole universe with his desire. In fact, many scientists have dedicated their entire lives to finding out how life came to be on Earth. He made the dry land and plants, on the fourth day. These were capable of hereditary function. Oparin. It contains huge galaxies. (vi) Anthropogenic evidences Excess use of herbicides, pesticides, etc has resulted in selection of resistant varieties in a lesser time scale. He made the fishes and the birds and on the sixth day, He formed the land animals and human beings. Louis Pasteur, a French scientist took broths in a long necked flask and then he bent the neck of the flask. So / к biogenesis is also disapproved. (d) A study of fossils in different sedimentary layers indicates the geological period in which they existed. ... Organic compounds first evolved in earth required for origin of life were. Following ancient theories are important to mention. Some of the ancient theories regarding the origin of life are as follows !

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