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The Berkeley Evolution Site Students and teachers who explore the Berkeley site will find resources to aid in understanding and teaching evolution. The materials are organized into optional learning paths such as “What did T. rex taste like?” Charles Darwin's theory of natural selection explains how animals who are better equipped to adapt biologically to changing environments survive longer and those who do not disappear. This process of biological evolution is the basis of science. What is Evolution? The term “evolution” has a variety of nonscientific meanings, such as “progress” or “descent with modification.” It is a scientific term that refers to the process of change of traits over time in organisms or species. This change is based in biological terms on natural selection and drift. Evolution is a key concept in the field of biology today. It is a theory that has been verified by thousands of scientific tests. In contrast to other theories in science like the Copernican theory or the germ theory of disease, evolution does not address questions of religion or the existence of God. 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 manner, as time passes. They referred to this as the “Ladder of Nature” or the scala naturae. 에볼루션 슬롯 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 asserts that different species of organisms have the same ancestry, which can be traced through fossils and other lines of evidence. This is the current understanding of evolution, which is supported by a variety of research lines in science, including molecular genetics. Scientists do not know how organisms have evolved, but they are confident that natural selection and genetic drift is the reason for the evolution of life. People with desirable traits are more likely to survive and reproduce, and they transmit their genes to the next generation. Over time, this results in gradual changes to the gene pool that gradually lead to new species and forms. Some scientists also use the term”evolution” to describe large-scale evolutionary changes such as the creation of a new species from an ancestral species. Certain scientists, including population geneticists, define evolution in a broad sense, referring to the net change in allele frequency over generations. Both definitions are acceptable and accurate, although some scientists argue that the allele-frequency definition omits crucial aspects of the evolutionary process. Origins of Life The development of life is a key stage in evolution. This occurs when living systems begin to evolve at the micro level – within individual cells, for example. The origins of life are an important subject in many areas such as biology and the field of chemistry. The question of how living things got their start is of particular importance in science due to it being an important challenge to the theory of evolution. It is often described as “the mystery of life,” or “abiogenesis.” Traditionally, the belief that life could emerge from nonliving things is known as spontaneous generation, or “spontaneous evolution.” This was a popular view before Louis Pasteur's experiments proved that it was impossible for the emergence of life to occur by the natural process. Many scientists still think it is possible to transition from living to nonliving substances. However, the conditions that are required are extremely difficult to reproduce in a laboratory. Researchers studying the beginnings of life are also interested in determining the physical properties of early Earth and other planets. Additionally, the evolution of life is a sequence of very complex chemical reactions that cannot be predicted from the fundamental physical laws on their own. These include the reading and replication of complex molecules, like DNA or RNA, to produce proteins that serve a specific function. These chemical reactions are often compared with the chicken-and-egg issue of how life came into existence with the appearance of DNA/RNA and protein-based cell machinery is essential for the beginning of life, however, without the appearance of life the chemical process that allows it is not working. Research in the area of abiogenesis requires collaboration among scientists from many different disciplines. This includes prebiotic scientists, astrobiologists and planet scientists. Evolutionary Changes The term “evolution” is commonly used today to refer to the accumulated changes in the genetic traits of an entire population over time. These changes may be the result of adaptation to environmental pressures as described in Darwinism. This process increases the frequency of genes that provide an advantage for survival in an animal, resulting in an overall change in the appearance of an entire group. These evolutionary changes are triggered by mutations, reshuffling genes in the process of sexual reproduction, and also by gene flow. Natural selection is the process that makes beneficial mutations more common. All organisms undergo changes and reshuffles of their genes. As mentioned above, those who have the advantageous characteristic have a higher reproduction rate than those who do not. Over many generations, this variation in the numbers of offspring born can result in a gradual shift in the number of advantageous characteristics in a particular population. This can be seen in the evolution of different beak shapes on finches from the Galapagos Islands. They have developed these beaks so they can get food more easily in their new habitat. These changes in the shape and form of organisms could also be a catalyst for the creation of new species. The majority of the changes that take place are the result of one mutation, but occasionally several will happen at the same time. The majority of these changes are not harmful or even harmful to the organism, however, a small proportion of them can have a positive impact on survival and reproduction, thus increasing their frequency in the population over time. This is the way of natural selection and it is able to be a time-consuming process that produces the cumulative changes that ultimately lead to the creation of a new species. Many people confuse evolution with the idea of soft inheritance which is the notion that traits inherited from parents can be changed by conscious choice or abuse. This is a misinterpretation of the biological processes that lead to the process of evolution. It is more accurate to say that evolution is a two-step, separate process that involves the forces of natural selection as well as mutation. 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. They were walking on two legs. Genetic and biological similarities suggest that we are closely related to chimpanzees. In fact we are the most closely with chimpanzees in the Pan genus, which includes bonobos and pygmy-chimpanzees. The last common ancestor between modern humans and chimpanzees dated 8 to 6 million years old. As time has passed, humans have developed a variety of traits, including bipedalism and the use fire. They also developed advanced tools. However, it is only in the last 100,000 years or so that most of the traits that distinguish us from other species have developed. These include a large brain that is complex human ability to build and use tools, as well as cultural diversity. Evolution occurs when genetic changes enable members of the group to better adapt to their environment. Natural selection is the process that triggers this adaptation. Certain characteristics are more desirable than others. The more adjusted are more likely to pass on their genes to the next generation. This is how all species evolve and is the basis of the theory of evolution. Scientists refer to this as the “law of natural selection.” The law states species that have a common ancestor are likely to develop similar characteristics as time passes. This is because these traits help them to reproduce and survive within their environment. All organisms have DNA molecules, which provides the information necessary to guide their growth and development. The structure of DNA is composed of base pair arranged in a spiral around phosphate and sugar molecules. The sequence of bases found in each strand determines the phenotype – the characteristic appearance and behavior of an individual. A variety of mutations and reshufflings of the genetic material (known as alleles) during reproduction causes variation in a group. Fossils from the first 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 notion that modern humans first came into existence in Africa. The fossil evidence and genetic evidence suggest that early humans migrated from Africa into Asia and then Europe.