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The Berkeley Evolution Site The Berkeley site contains resources that can help students and teachers understand and teach evolution. The resources are organized into optional learning paths like “What did T. rex taste like?” Charles Darwin's theory of natural selection explains that over time, animals that are more adaptable to changing environments thrive, and those that do not become extinct. Science is concerned with the process of biological evolution. What is Evolution? The term “evolution” could have a variety of meanings that are not scientific. For instance, it can mean “progress” and “descent with modifications.” 에볼루션 Evolution KR is a scientific term that refers to the process of changing traits over time in organisms or species. This change is based in biological terms on natural selection and drift. Evolution is a central tenet of modern biology. It is a theory that has been tested and proven by thousands of scientific tests. Evolution does not deal with the existence of God or religious beliefs like other theories in science, like the Copernican or germ theory of diseases. Early evolutionists, including Jean-Baptiste Lamarck and Erasmus Darwin (Charles's grandfather), believed that certain physical characteristics were predetermined to change, in a step-like way, over time. They referred to this as the “Ladder of Nature” or scala naturae. Charles Lyell used the term to describe this idea in his Principles of Geology, first published in 1833. Darwin published his theory of evolution in his book On the Origin of Species, written in the early 1800s. It claims that different species of organisms have an ancestry that can be determined through fossils and other evidence. This is the current view of evolution, and is supported by many lines of research in science that include molecular genetics. Scientists do not know how organisms evolved but they are sure that natural selection and genetic drift is responsible for the evolution of life. Individuals with advantageous traits are more likely to survive and reproduce, and they pass their genes on to the next generation. Over time, the gene pool gradually changes and develops into new species. Some scientists employ the term evolution in reference to large-scale changes, such the development of an animal from an ancestral one. Others, like population geneticists, define it more broadly by referring the net variation in the frequency of alleles over generations. Both definitions are acceptable and accurate however, some scientists claim that the definition of allele frequency is lacking essential aspects of the evolution process. Origins of Life A key step in evolution is the development of life. The beginning of life takes place when living systems start to evolve at a micro level, like within individual cells. The origin of life is an issue in a variety of disciplines, including biology, chemistry, and geology. The question of how living organisms began is a major topic in science since it poses an enormous challenge to the theory of evolution. It is often referred to “the mystery” of life or “abiogenesis.” The idea that life could be born from non-living things was called “spontaneous generation” or “spontaneous evolutionary”. This was a common belief prior to Louis Pasteur's experiments proved that the development of living organisms was not possible by the natural process. Many scientists believe that it is possible to make the transition from nonliving materials to living. The conditions necessary for the creation of life are difficult to replicate in a laboratory. This is why researchers studying the nature of life are also keen to understand the physical properties of early Earth and other planets. Additionally, the evolution of life is dependent on a sequence of very complex chemical reactions that cannot be predicted based on basic physical laws alone. These include the reading and the replication of complex molecules, like DNA or RNA, to produce proteins that perform a particular function. These chemical reactions are often compared with the chicken-and-egg dilemma of how life began: The development of DNA/RNA as well as proteins-based cell machinery is vital for the onset of life, but without the emergence of life the chemical reaction that is the basis for it is not working. Research in the area of abiogenesis requires collaboration among scientists from many different disciplines. This includes prebiotic chemists the astrobiologists, the planet scientists geophysicists and geologists. Evolutionary Changes The term “evolution” is typically used today to refer to the accumulated changes in the genetic traits of an entire population over time. These changes can result from adaptation to environmental pressures as discussed in the entry on Darwinism (see the entry on Charles Darwin for background), or from natural selection. This process increases the number of genes that provide the advantage of survival for the species, leading to an overall change in the appearance of an entire group. The specific mechanisms responsible for these evolutionary changes include mutation, reshuffling of genes during sexual reproduction, as well as gene flow between populations. While reshuffling and mutations of genes occur in all organisms, the process by which beneficial mutations become more common is called natural selection. This happens because, as we've mentioned earlier, those individuals with the advantageous trait are likely to have a higher reproductive rate than those with it. Over the course of many generations, this variation in the number of offspring born could result in a gradual shift in the average number of advantageous traits within a group of. One good example is the growth of the size of the beaks on different species of finches found on the Galapagos Islands, which have developed different beak shapes to enable them to more easily access food in their new habitat. These changes in form and shape can aid in the creation of new organisms. The majority of changes are caused by one mutation, however sometimes multiple occur at once. The majority of these changes are not harmful or even harmful to the organism, however, a small proportion of them can be beneficial to the survival of the organism and its reproduction, thereby increasing the frequency of these changes in the population over time. Natural selection is a mechanism that could result in the accumulation of change over time that leads to the creation of a new species. Many people mistakenly associate evolution with the concept of soft inheritance which is the notion that inherited traits can be altered by conscious choice or abuse. This is a misunderstood understanding of the nature of evolution, and of the actual biological processes that trigger it. A more accurate description of evolution is that it is a two-step process which involves the separate and often conflicting forces of mutation and natural selection. Origins of Humans Humans of today (Homo Sapiens) evolved from primates, a group of mammal species which includes chimpanzees as well as gorillas. Our ancestral ancestors were walking on two legs, as shown by the earliest fossils. Biological and genetic similarities indicate that we have a close relationship with the chimpanzees. In reality we are the most closely related to the chimpanzees within the Pan Genus, which includes bonobos and pygmy-chimpanzees. The last common human ancestor and chimpanzees was born between 8 and 6 million years ago. In the course of time humans have developed a number of characteristics, including bipedalism and the use of fire. They also invented advanced tools. However, it is only in the last 100,000 years or so that most of the important traits that distinguish us from other species have emerged. They include language, a large brain, the capacity to build and use complex tools, as well as the diversity of our culture. The process of evolution occurs when genetic changes allow individuals of a population to better adapt to their environment. Natural selection is the process that drives this adaptation. Certain characteristics are more desirable than others. The ones who are better adjusted are more likely to pass on their genes to the next generation. This is how all species evolve and is the foundation for the theory of evolution. Scientists call it the “law of natural selection.” The law states that species which have a common ancestor, tend to develop similar characteristics over time. This is because the characteristics make it easier for them to live and reproduce in their environments. Every living thing has a DNA molecule that contains the information needed to control their growth and development. The DNA structure is composed of base pair that are arranged in a spiral around sugar and phosphate molecules. The sequence of bases within each string determines the phenotype or the characteristic appearance and behavior of a person. Different mutations and reshufflings of the genetic material (known as alleles) during sexual reproduction can cause variation in a group. Fossils from the early human species Homo erectus, as well as Homo neanderthalensis have been found in Africa, Asia and Europe. Although there are some differences, these fossils all support the hypothesis that modern humans first appeared in Africa. Genetic and fossil evidence also suggest that early humans migrated from Africa into Asia and then Europe.