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The Berkeley Evolution Site The Berkeley site offers resources that can assist students and teachers learn about and teach evolution. The materials are organized in different learning paths like “What does T. rex look like?” Charles Darwin's theory of natural selection explains that over time, animals that are more adaptable to changing environments do better than those that don't become extinct. Science is concerned with this process of biological evolution. What is Evolution? The word evolution has many nonscientific meanings. For instance “progress” or “descent with modification.” Scientifically, it refers to a change in the characteristics of organisms (or species) over time. This change is based in biological terms on natural selection and drift. Evolution is a fundamental tenet in modern biology. It is an established theory that has stood up to the test of time and thousands of scientific experiments. Unlike many other scientific theories like the Copernican theory or the germ theory of disease, the evolution theory is not a discussion 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 characteristics were predetermined to change in a gradual manner over time. They referred to this as the “Ladder of Nature” or the scala naturae. Charles Lyell used the term to describe this concept in his Principles of Geology, first published in 1833. Darwin presented his theory of evolution in his book On the Origin of Species, written in the early 1800s. It states that all species of organisms have common ancestors that can be traced through fossils and other evidence. This is the current view of evolution that is supported by many lines of scientific research, including molecular genetics. Scientists don't know how organisms evolved, but they are confident that natural selection and genetic drift are the primary reason for the evolution of life. Individuals with advantageous traits are more likely to survive and reproduce, and these individuals pass their genes on to the next generation. As time passes the gene pool slowly changes and evolves into new species. Certain scientists use the term”evolution” in reference to large-scale changes, like the development of one species from an ancestral one. Others, like population geneticists, define evolution more broadly by referring to a net variation in the frequency of alleles over generations. Both definitions are accurate and acceptable, however some scientists argue that allele-frequency definitions miss important aspects of the evolution. Origins of Life The emergence of life is a crucial stage in evolution. This occurs when living systems begin to develop at the micro level, within individual cells, for example. The origins of life are an important issue in many fields that include biology and chemistry. The question of how living things started has a special place in science due to it being a major challenge to the theory of evolution. It is sometimes referred to as “the mystery” of life or “abiogenesis.” Traditionally, the idea that life could emerge from nonliving things is known as spontaneous generation or “spontaneous evolution.” 에볼루션 룰렛 was a common belief before Louis Pasteur's research showed that it was impossible for the development of life to happen through an entirely natural process. Many scientists still believe it is possible to go from nonliving substances to living. However, the conditions needed are extremely difficult to reproduce in labs. Researchers investigating the origins of life are also keen to understand the physical properties of early Earth and other planets. Furthermore, the growth of life is the sequence of extremely complex chemical reactions that cannot be predicted from basic physical laws on their own. These include the transformation of long information-rich molecules (DNA or RNA) into proteins that carry out some function as well as the replication of these intricate molecules to produce new DNA or RNA sequences. These chemical reactions are comparable to a chicken-and egg problem: the emergence and development of DNA/RNA, the protein-based cell machinery, is essential for the onset life. But without life, the chemistry that is required to enable it appears to be working. Research in the field of abiogenesis requires cooperation among scientists from many different disciplines. This includes prebiotic scientists, astrobiologists and planet scientists. Evolutionary Changes Today, the word evolution is used to describe the cumulative changes in genetic characteristics over time. These changes may be the result of adapting to environmental pressures, as discussed in Darwinism. This process increases the frequency of genes that offer the advantage of survival for a species, resulting in an overall change in the appearance of a group. These evolutionary changes are triggered by mutations, reshuffling of genes in the process of sexual reproduction, and also by the flow of genes. While mutation and reshuffling of genes occur in all organisms, the process by which beneficial mutations become more common is known as natural selection. This is because, as mentioned above those with the advantageous trait are likely to have a higher reproductive rate than those who do not have it. Over many generations, this difference in the number of offspring born could result in an inclination towards a shift in the average number of advantageous characteristics in a particular population. One good example is the increase in beak size on different species of finches on the Galapagos Islands, which have developed beaks with different shapes to allow them to more easily access food in their new habitat. These changes in shape and form can also help create new organisms. Most of the changes that take place are caused by a single mutation, but occasionally several will happen at once. The majority of these changes could be neutral or even harmful however, a small percentage could have a positive impact on survival and reproduce, increasing their frequency as time passes. This is the process of natural selection, and it could be a time-consuming process that produces the accumulating changes that eventually result in an entirely new species. Many people confuse the concept of evolution with the idea that inherited characteristics can be altered by conscious choice or by use and abuse, a notion called soft inheritance. This is a misinterpretation of the biological processes that lead to the process of evolution. It is more precise to say that evolution is a two-step, independent process, which involves the forces of natural selection and mutation. Origins of Humans Humans of today (Homo sapiens) evolved from primates – a species of mammals that also includes gorillas, chimpanzees, and bonobos. Our ancestral ancestors were walking on two legs, as shown by the earliest fossils. Genetic and biological similarities show that we share an intimate relationship with chimpanzees. In actual fact we are the closest related to the chimpanzees within the Pan genus that includes pygmy and bonobos and pygmy chimpanzees. The last common human ancestor as well as chimpanzees was between 8 and 6 million years ago. Humans have evolved a variety of traits over time including bipedalism, the use of fire, and the development of advanced tools. However, it is only in the last 100,000 years or so that the majority of the essential traits that distinguish us from other species have developed. These include a large brain that is complex human ability to create and use tools, and cultural variety. Evolution occurs when genetic changes enable members of a group to better adapt to their environment. This adaptation is driven by natural selection, a process that determines certain traits are more desirable than other traits. The ones who are better adjusted are more likely to pass on their genes to the next generation. This is the way all species evolve and the foundation for the theory of evolution. Scientists call this the “law of natural selection.” The law states that species which have an ancestor in common will tend to develop similar traits in the course of time. This is because those traits make it easier for them to survive and reproduce in their environment. All organisms have DNA molecules, which provides the information necessary to guide their growth and development. The structure of DNA is made of base pairs arranged in a spiral around sugar and phosphate molecules. The sequence of bases within each strand determines the phenotype, the distinctive appearance and behavior of an individual. The variations in a population are caused by reshufflings and mutations of genetic material (known collectively as alleles). Fossils of the first human species, Homo erectus and Homo neanderthalensis were discovered in Africa, Asia, and Europe. These fossils, despite some differences in their appearance, all support the idea that modern humans' ancestors originated in Africa. The evidence from fossils and genetics suggests that early humans left Africa and moved to Asia and Europe.