Ibrahim Ali Posted May 14 Report Share Posted May 14 The theory of evolution has been one of the debated topics in the history of science. The idea that all living organism evolved over million of years through a process of natural selection and adaptation has brought controversy among individuals who have different beliefs and point of view. The theory of evolution is a profound scientific concept, characterized by strong evidences that makes it impossible to ignore, some accepted it as scientific fact while other rejected it entirely. Firstly, Evolution is the sum of total adaptive change that has taken place over a long period of time leading to the development of new species from earlier ones (living in different way from the species which they evolved), and many earliest species extinct in this never ending process. In 19th century the idea of evolution(that living organism are descended from common ancestors) had occur to a number of scientists. In 1809 the Franch biologist, Lamarck published the first theory of evolution, and his work spread the idea of evolution, although his theory was disproved. Then, in 1859 the British naturalist Charles Darwin published his book that revolutionized the science of biology. This famous book on the origin of species by means of natural selection, outlined how present-day organisms evolved from earlier ones. The modern view of evolution combines Darwin's theory with our present-day knowledge of genetics and molecular biology. From the Darwin's theory, we can get to know that all living organism are involved in a struggle for existence, those that tend to survive in a population and reproduces are the individuals whose variation give them competitive advantage over the rest. They are fitted and best to adapted in their environment. The favourable variation the possess are passed to their offspring. Thus, identified environmental pressure as the main cause of natural selection, they cause favourable variations to accumulated and unfavourable ones to be weeded out, over a long period of time favourable variations naturally selected to the environment, and sufficiently bring about existence of new species. Darwin's did not know how inheritance works so he could not explain the source of variation and how individual variation arise, but later after the work of an Austrian monk Gregor Mendel who first outlined how inheritance works, then the neo-darwinism arise. The current theory of evolution (neo-darwinism) also postulated that although natural selection is the only force that regularly produces adaptive evolutionary, other forces too play role in the process. Scientists now identified mutation, gene flow, genetic drift as the other natural forces that are responsible for the change. Mutation: the random change in DNA that alter genetic information and so introduced new characteristics is called mutation. A mutation is the only process that actually change genes, so they are ultimate source that provided raw materials for evolution. And, gene flow occur when member of population interbreed, genes are combined in different ways and spread in the population bringing about arising new characteristics, this occur only between members of the same species. So occurrence of this for long period of time can bring about existence of new species. Then, in genetic drift some genes may spread more than others, and bring about extinction of low spreadable genes and arising of new characteristic. The four forces discussed so far( natural selection, mutation, genes flow and genetic drift) act alone or in combination to determined the course and rate of evolution. It was explains that 570 millions of years ago only algae, fungi are found, then after change in the environments and with the reasons of the four force discussed so far, later after other millions of years, algae and invertebrates came to exist, and after other millions of years more invertebrates and jawles fishes came to exist, then primitive land plant came to exist, then land plants and more fishes became common, amphibians appeared, then amphibians became common insects and fern trees appeared, then primitive reptiles, then forest cyan and conifers became common, first dinosaurs, marine reptiles, and primitive mammals appeared, then more reptiles and first bird appeared, then flowering plant, extinction of dinosaurs, birds and small mammals appeared, then grassland mammals, and about 65 millions years ago first humans appeared. In my observation, I need thousands of questions to answered for me to belief in the above theory, few are:- 1: Man came to exist millions of years ago, so how man know the time of his existence? 2:From what first ancestor of all organism exist? In conclusion; have you believed, or yet to believe of the so far discussed theory. Quote Link to comment
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