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The Berkeley Evolution Site Students and teachers who explore the Berkeley site will find a wealth of resources to aid in understanding and teaching evolution. The resources are arranged into different learning paths, such as “What did T. rex taste like?” Charles Darwin's theory of natural selection explains how creatures who are better able to adapt biologically to a changing environments survive longer and those that don't become extinct. This process of evolution is the basis of science. What is Evolution? The word evolution has many nonscientific meanings, such as “progress” or “descent with modification.” Scientifically it refers to a process of change in the characteristics of living things (or species) over time. In biological terms, this change is due to natural selection and genetic drift. Evolution is a fundamental tenet in the field of biology today. It is a concept that has been confirmed by a myriad of scientific tests. Unlike many other scientific theories like the Copernican theory or the germ theory of disease, the evolution theory does not address questions of religion 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 evolve in a step-like fashion over time. They called this 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 presented his theory of evolution in his book On the Origin of Species which was written in the early 1800s. It states that all species of organisms share a common ancestry which can be traced through fossils and other evidence. This is the current perspective on evolution, and is supported in a wide range of areas of science, including molecular biology. Scientists aren't sure how organisms have evolved however they are certain that natural selection and genetic drift is the reason for the evolution of life. Individuals with advantageous traits are more likely to live and reproduce, and they pass their genes on to the next generation. In time, this results in a gradual accumulation of changes to the gene pool that gradually create new species and types. Some scientists use the term evolution in reference to large-scale changes, like the development of one species from an ancestral one. Other scientists, such as population geneticists, define the term “evolution” more broadly by referring a net change in the frequency of alleles across generations. Both definitions are accurate and acceptable, but some scientists believe that allele-frequency definitions do not include important aspects of evolutionary process. Origins of Life A key step in evolution is the development of life. This happens when living systems begin to develop at a micro-level – within individual cells, for example. The origins of life is an issue in a variety of disciplines such as biology, chemistry and geology. The nature of life is a subject of interest in science because it challenges the theory of evolution. It is often described as “the mystery of life,” or “abiogenesis.” Traditionally, the belief that life can arise from nonliving things is called spontaneous generation or “spontaneous evolution.” 에볼루션 블랙잭 was a common belief before Louis Pasteur's experiments showed that it was impossible for the emergence of life to happen through the natural process. Many scientists still believe that it is possible to transition from nonliving substances to living. However, the conditions required are extremely difficult to reproduce in labs. This is why researchers studying the beginnings of life are also interested in understanding the physical properties of early Earth and other planets. Furthermore, the growth of life depends on an intricate sequence of chemical reactions that can't be predicted from basic physical laws on their own. These include the reading of long information-rich molecules (DNA or RNA) into proteins that perform some function as well as the replication of these complex molecules to produce new DNA or RNA sequences. These chemical reactions are comparable to the chicken-and-egg problem that is the emergence and growth of DNA/RNA, the protein-based cell machinery, is essential to begin the process of becoming a living organism. However, without life, the chemistry required to make it possible appears to be working. Abiogenesis research requires collaboration with scientists from various disciplines. This includes prebiotic scientists, astrobiologists and planetary scientists. Evolutionary Changes The word evolution is usually used to describe the accumulated changes in the genetic characteristics of populations over time. These changes could be the result of the adaptation to environmental pressures as discussed in Darwinism. This process increases the number of genes that offer the advantage of survival for a species, resulting in an overall change in the appearance of the group. These changes in evolutionary patterns are caused by mutations, reshuffling genes in the process of sexual reproduction, and also by gene flow. Natural selection is the process that allows beneficial mutations to become more common. All organisms undergo changes and reshuffles in their genes. This occurs because, as we've mentioned earlier those who have the advantageous trait are likely to have a higher reproductive rate than those who do not have it. This difference in the number of offspring produced over a long period of time can result in a gradual change in the average number of beneficial characteristics in a group. One good example is the increase in beak size on different species of finches found 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 the shape and appearance of organisms can also help create new species. The majority of the changes that take place are the result of one mutation, however occasionally, multiple mutations occur simultaneously. The majority of these changes could be neutral or even harmful, but a small number could have a positive impact on survival and reproduction and increase their frequency as time passes. This is the mechanism of natural selection, and it is able to, over time, produce the gradual changes that eventually result in a new species. Some people think that evolution is a form of soft inheritance which is the notion that traits inherited from parents 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 lead to it. It is more accurate to say that the process of evolution is a two-step, separate process, that is influenced by the forces of natural selection as well as mutation. Origins of Humans Modern humans (Homo Sapiens) evolved from primates, which is a group of mammal species which includes chimpanzees and gorillas. Our ancestors walked on two legs, as evidenced by the earliest fossils. Genetic and biological similarities suggest that we are closely related to Chimpanzees. In fact, we are most closely with chimpanzees in the Pan genus, which includes bonobos and pygmy-chimpanzees. The last common human ancestor and chimpanzees lived between 8 and 6 million years ago. As time has passed humans have developed a range of characteristics, such as bipedalism and the use of fire. They also developed advanced tools. It is only in the past 100,000 years or so that most of the traits that distinguish us from other species have emerged. They include language, a large brain, the ability to build and use sophisticated tools, and a cultural diversity. The process of evolution occurs when genetic changes allow individuals in a group to better adapt to their environment. This adaptation is triggered by natural selection, a process that determines certain traits are more desirable than others. Those with the better adaptations are more likely to pass on their genes to the next generation. This is how all species evolve and is the basis for the theory of evolution. Scientists refer to this as the “law of natural selection.” The law says that species that have a common ancestor, tend to develop similar traits over time. This is because these characteristics make it easier for them to survive and reproduce in their environments. All organisms possess the DNA molecule, which contains the information needed to control their growth. The DNA molecule consists of base pairs arranged spirally around sugar molecules and phosphate molecules. The sequence of bases within each strand determines the phenotype or the individual's unique appearance and behavior. Variations in a population can be caused by reshufflings and mutations of genetic material (known collectively as alleles). Fossils from the earliest human species, Homo erectus and Homo neanderthalensis were discovered in Africa, Asia, and Europe. These fossils, despite differences in their appearance all support the theory that modern humans' ancestors originated in Africa. The genetic and fossil evidence suggests that early humans left Africa and moved to Asia and Europe.