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에볼루션사이트 Site The Berkeley site has resources that can help students and teachers learn about and teach evolution. The materials are arranged in various learning paths that can be used in a variety of ways for example “What does T. rex look like?” Charles Darwin's theory of natural selection explains how over time, animals that are more adaptable to changing environments survive and those that are not extinct. This process of biological evolution is what science is all about. What is Evolution? The term “evolution” could have many nonscientific meanings. For instance it could refer to “progress” and “descent with modifications.” It is an academic term that is used to describe the process of change of characteristics over time in organisms or species. In terms of biology the change is caused by natural selection and genetic drift. Evolution is one of the fundamental tenets of modern biology. It is a concept that has been proven by thousands of scientific tests. Unlike many other scientific theories, such as the Copernican theory or the germ theory of disease, the evolution theory does not address questions of religious belief or the existence of God. Early evolutionists such as Erasmus Darwin (Charles’s grandfather) and Jean-Baptiste Lamarck believed that certain physical traits were predetermined to change in a step-like fashion over time. This was referred to as the “Ladder of Nature”, or scala Naturae. Charles Lyell used the term to describe this concept in his Principles of Geology, first published in 1833. In the early 1800s, Darwin formulated his theory of evolution and published it in his book On the Origin of Species. It states that all species of organisms share a common ancestry, which can be proven through fossils and other lines of evidence. This is the current understanding of evolution, and is supported by many lines of scientific research which includes molecular genetics. Although scientists aren't able to determine exactly how organisms developed however they are sure that the evolution of life on earth is the result of natural selection and genetic drift. People with advantages are more likely to survive and reproduce. These individuals then pass their genes on to the next generation. Over time this leads to an accumulation of changes in the gene pool which gradually result in new species and types. Some scientists also employ the term”evolution” to describe large-scale evolutionary changes such as the creation of a new species from an ancestral species. Some scientists, like population geneticists define evolution in a broader sense by talking about the net change in the frequency of alleles across generations. Both definitions are acceptable and precise however, some scientists claim that the allele-frequency definition is missing essential aspects of the evolution process. Origins of Life The development of life is a key step in evolution. The emergence of life happens when living systems start to develop at a micro level, like within individual cells. The origins of life are an issue in a variety of disciplines that include geology, chemistry, biology and chemistry. The nature of life is an area of great interest in science because it challenges the theory of evolution. It is sometimes referred to “the mystery” of life or “abiogenesis.” Traditionally, the belief that life can emerge from nonliving things is known as spontaneous generation, or “spontaneous evolution.” This was a common belief before Louis Pasteur's experiments proved that it was impossible for the emergence of life to happen through a purely natural process. Many scientists believe that it is possible to transition from nonliving substances to life. The conditions required to make life are not easy to reproduce in a lab. Researchers studying the nature of life are also interested in understanding the physical properties of the early Earth and other planets. In addition, the development of life is dependent on a sequence of very complex chemical reactions that cannot be predicted based on basic physical laws on their own. These include the reading and re-reading of complex molecules, like DNA or RNA, to create proteins that perform a specific function. These chemical reactions are often compared with the chicken-and-egg issue of how life began in the first place. The development of DNA/RNA as well as protein-based cell machinery is essential for the onset of life, but without the emergence of life the chemical process that allows it is not working. Abiogenesis research requires collaboration with scientists from different disciplines. This includes prebiotic scientists, astrobiologists, and planet scientists. Evolutionary Changes The word evolution is usually used to describe the cumulative changes in the genetic characteristics of a population over time. These changes can be the result of adaptation to environmental pressures as described in Darwinism. The latter is a mechanism that increases the frequency of those genes which confer an advantage in survival over other species which results in gradual changes in the appearance of a group. These changes in evolutionary patterns are caused by mutations, reshuffling of genes in the process of sexual reproduction, and also by the flow of genes. Natural selection is the process that allows beneficial mutations to become more common. All organisms undergo mutations and reshuffles in their genes. This is because, as we've mentioned earlier, those individuals with the advantageous trait are likely to have a higher reproduction rate than those who do not have it. This difference in the number of offspring born over a number of generations could result in a gradual change in the average number of beneficial traits within a group. This can be seen in the evolution of various beak shapes on finches from the Galapagos Islands. They have created these beaks to ensure that they can access food more quickly in their new home. These changes in the form and shape of living organisms may also aid in the creation of new species. The majority of changes are caused by a single mutation, however sometimes multiple occur simultaneously. The majority of these changes are not harmful or even harmful to the organism, but a small percentage can be beneficial to survival and reproduction, thus increasing their frequency in the population over time. This is the mechanism of natural selection and it is able to, over time, produce the gradual changes that eventually result in an entirely new species. Many people mistakenly associate evolution with the concept of soft inheritance which is the notion that inherited traits can be changed by conscious choice or by abuse. This is a misunderstanding of the nature of evolution and of the actual biological processes that trigger it. A more accurate description of evolution is that it involves a two-step process, which involves the separate and often antagonistic forces of mutation and natural selection. Origins of Humans Humans of today (Homo sapiens) evolved from primates – a group of mammals that includes chimpanzees, gorillas, and bonobos. The earliest human fossils prove that our ancestors were bipeds – walkers on two legs. Biological and genetic similarities indicate that we share an intimate relationship with chimpanzees. In reality we are the closest with chimpanzees in the Pan Genus that includes pygmy and bonobos and pygmy-chimpanzees. The last common ancestor of modern humans and chimpanzees lived between 8 and 6 million years ago. Over time humans have developed a range of characteristics, including bipedalism and the use of fire. They also invented advanced tools. But it's only in the last 100,000 years or so that the majority of the important characteristics that differentiate us from other species have developed. They include language, a large brain, the capacity to build and use complex tools, as well as cultural diversity. Evolution occurs when genetic changes allow members of the group to better adapt to their environment. This adaptation is driven by natural selection, a process whereby certain traits are preferred over other traits. The more adjusted are more likely to pass on their genes to the next generation. This is how all species evolve, and the basis of the theory of evolution. Scientists refer to this as the “law of natural selection.” The law states species that share an ancestor will tend to acquire similar traits as time passes. This is because these traits make it easier to live and reproduce in their environment. All organisms have DNA molecules, which provides the information necessary to control their growth and development. The DNA molecule is made up of base pairs arranged spirally around phosphate molecules and sugar molecules. The sequence of bases within each strand determines phenotype which is the person's distinctive appearance and behavior. Variations in a population are caused by mutations and reshufflings of genetic material (known collectively as alleles). Fossils of the first human species, Homo erectus and Homo neanderthalensis have been discovered in Africa, Asia, and Europe. These fossils, despite a few differences in their appearance, all support the idea of the origins of modern humans in Africa. Evidence from fossils and genetics suggest that early humans came from Africa into Asia and then Europe.