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Presentation on- Life on the earth by Anas ahmad

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ACKNOWLEDGEMENT I AM ANAS AHMAD OF CLASS 10 TH . THIS PROJECT IS GIVEN BY SCIENCE TEACHER. I HAVE CHOOSEN THE TOPIC LIFE ON EARTH. TO COMPLETE THIS OROJECT I HAVE TAKEN THE HELP OF BOKS AND INTERNET.

Biologists reason that all living organisms on Earth must share a single last universal ancestor, because it would be virtually impossible that two or more separate lineages could have independently developed the many complex biochemical mechanisms common to all living organisms:

Biologists reason that all living organisms on Earth must share a single last universal ancestor, because it would be virtually impossible that two or more separate lineages could have independently developed the many complex biochemical mechanisms common to all living organisms Origins of life on Earth

The idea that life on Earth was "seeded" from elsewhere in the Universe dates back at least to the Greek philosopher Anaximander in the sixth century BCE. In the twentieth century it was proposed by the physical chemist Svante Arrhenius, by the astronomers Fred Hoyle and Chandra:

The idea that life on Earth was "seeded" from elsewhere in the Universe dates back at least to the Greek philosopher Anaximander in the sixth century BCE . In the twentieth century it was proposed by the physical chemist Svante Arrhenius , by the astronomers Fred Hoyle and Chandra Life "seeded" from elsewhere

Life on Earth is based on carbon and water. Carbon provides stable frameworks for complex chemicals and can be easily extracted from the environment, especially from carbon dioxide. The only other element with similar chemical properties, silicon, forms much less stable structures and, because most of its compounds are solids, would be more difficult for organisms to extract. :

Life on Earth is based on carbon and water. Carbon provides stable frameworks for complex chemicals and can be easily extracted from the environment, especially from carbon dioxide. The only other element with similar chemical properties, silicon, forms much less stable structures and, because most of its compounds are solids, would be more difficult for organisms to extract. Independent emergence on Earth

Even the simplest members of the three modern domains of life use DNA to record their "recipes" and a complex array of RNA and protein molecules to "read" these instructions and use them for growth, maintenance and self-replication. This system is far too complex to have emerged directly from non-living materials.[37] The discovery that some RNA molecules can catalyze both their own replication and the construction of proteins led to the hypothesis of earlier life-forms based entirely on RNA.:

Even the simplest members of the three modern domains of life use DNA to record their "recipes" and a complex array of RNA and protein molecules to "read" these instructions and use them for growth, maintenance and self-replication. This system is far too complex to have emerged directly from non-living materials.[37] The discovery that some RNA molecules can catalyze both their own replication and the construction of proteins led to the hypothesis of earlier life-forms based entirely on RNA. Replication first: RNA world

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A series of experiments starting in 1997 showed that early stages in the formation of proteins from inorganic materials including carbon monoxide and hydrogen sulfide could be achieved by using iron sulfide and nickel sulfide as catalysts. Most of the steps required temperatures of about 100 °C (212 °F) and moderate pressures, although one stage required 250 °C (482 °F) and a pressure equivalent to that found under 7 kilometres (4.3 mi) of rock. Metabolism first: Iron–sulfur world Metabolism first: Ir on–sulfur w orl d

RNA is complex and there are doubts about whether it can be produced non-biologically in the wild.[56] Some clays, notably montmorillonite, have properties that make them plausible accelerators for the emergence of an RNA world: they grow by self-replication of their crystalline pattern; they are subject to an analog of natural selection, as the clay "species" that grows fastest in a particular environment rapidly becomes dominant; and they can catalyze the formation of RNA molecules:

RNA is complex and there are doubts about whether it can be produced non-biologically in the wild.[56] Some clays, notably montmorillonite , have properties that make them plausible accelerators for the emergence of an RNA world: they grow by self-replication of their crystalline pattern; they are subject to an analog of natural selection, as the clay "species" that grows fastest in a particular environment rapidly becomes dominant; and they can catalyze the formation of RNA molecules The clay theory

Modern humans evolved from a lineage of upright-walking apes that has been traced back over 6 Ma to Sahelanthropus.[179] The first known stone tools were made about 2.5 Ma, apparently by Australopithecus garhi, and were found near animal bones that bear scratches made by these tools.[180] The earliest hominines had chimp-sized brains, but there has been a fourfold increase in the last 3 Ma; a statistical analysis suggests that hominine brain sizes depend almost completely on the date of the fossils, while the species to which they are assigned has only slight influence.:

Modern humans evolved from a lineage of upright-walking apes that has been traced back over 6 Ma to Sahelanthropus .[179] The first known stone tools were made about 2.5 Ma, apparently by Australopithecus garhi , and were found near animal bones that bear scratches made by these tools.[180] The earliest hominines had chimp-sized brains, but there has been a fourfold increase in the last 3 Ma; a statistical analysis suggests that hominine brain sizes depend almost completely on the date of the fossils, while the species to which they are assigned has only slight influence. Humans

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