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The Berkeley Evolution Site The Berkeley site has resources that can help students and teachers understand and teach evolution. The resources are arranged into different learning paths such as “What did T. rex taste like?” Charles Darwin's theory on natural selection explains how creatures who are better able to adapt biologically to changing environment survive over time and those who do not become extinct. Science is about this process of biological evolutionary change. What is Evolution? The term “evolution” can have many nonscientific meanings. For example, it can mean “progress” and “descent with modifications.” Scientifically, it refers to a process of changes in the traits of living organisms (or species) over time. In terms of biology, this change is based on natural selection and genetic drift. Evolution is a central tenet of modern biology. It is an accepted theory that has stood up to the test of time and a multitude of scientific experiments. Evolution does not deal with God's presence or spiritual beliefs in the same way as other scientific theories such as the Copernican or germ theory of disease. Early evolutionists, such as Erasmus Darwin (Charles’s grandfather) and Jean-Baptiste Lamarck believed that certain physical traits 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 concept in his Principles of Geology, first published in 1833. 에볼루션 코리아 published his theory of evolution in his book On the Origin of Species published in the early 1800s. It states that all species of organisms have an ancestry that can be traced by fossils and other evidence. This is the current perspective on evolution, which is supported in many areas of science that include molecular biology. Scientists aren't sure how organisms evolved, but they are confident that natural selection and genetic drift are responsible for the development of life. People with desirable 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 gradually changes and develops into new species. Certain scientists also use the term evolution to describe large-scale evolutionary changes such as the creation of the new species from an ancestral species. Others, like population geneticists, define evolution more broadly by referring an overall change in the frequency of alleles across generations. Both definitions are valid and reliable, although some scientists argue that the allele-frequency definition is missing important features of the evolutionary process. Origins of Life The birth of life is a key step in the process of evolution. The emergence of life happens when living systems start to develop at a microscopic level, such as within individual cells. The origin of life is an important topic in many disciplines, including biology and the field of chemistry. The nature of life is an area that is of immense interest to scientists, as it is a challenge to the theory of evolution. It is often referred to as “the mystery of life” or “abiogenesis.” The idea that life could emerge from non-living matter was known as “spontaneous generation” or “spontaneous evolutionary”. It was a common belief prior to Louis Pasteur's tests proved that the emergence of living organisms was not achievable through a natural process. Many scientists still think it is possible to transition from nonliving substances to living ones. The conditions required for the creation of life are difficult to reproduce in a lab. Researchers interested in the origins and development of life are also eager to learn about the physical characteristics of the early Earth as well as other planets. The life-cycle of a living organism is also dependent on a series of complex chemical reactions, which are not predicted by simple physical laws. These include the reading and replication of complex molecules, such as DNA or RNA, to create proteins that perform a particular function. These chemical reactions can be compared to the chicken-and-egg problem which is the development and emergence of DNA/RNA, the protein-based cell machinery, is necessary for the beginning of life. Although, without life, the chemistry required to make it possible appears to be working. Abiogenesis research requires collaboration among scientists from different disciplines. This includes prebiotic scientists, astrobiologists and planet scientists. Evolutionary Changes The term “evolution” is typically used today to describe the accumulated changes in the genetic characteristics of an entire population over time. These changes can be the result of adapting to environmental pressures, as discussed in Darwinism. This latter mechanism increases the frequency of genes that confer the advantage of survival for an animal, resulting in an overall change in the appearance of an entire group. The specific mechanisms behind these evolutionary changes are mutation or reshuffling genes during sexual reproduction, and gene flow between populations. Natural selection is the process that allows beneficial mutations to become more common. All organisms undergo mutations and reshuffles of genes. As noted above, individuals who possess the desirable trait have a higher reproductive rate than those who don't. This differential in the number of offspring that are produced over a number of generations could result in a gradual shift in the average number of beneficial traits in the group. This is evident in the evolution of different beak shapes for finches from the Galapagos Islands. They have developed these beaks so that they can access food more quickly in their new home. These changes in the form and shape of organisms could also help create new species. The majority of the changes that occur are the result of one mutation, however occasionally, multiple mutations occur at once. Most of these changes are not harmful or even detrimental to the organism, however, a small proportion of them can have an advantageous impact on the survival of the organism and its reproduction, thereby increasing their frequency in the population over time. Natural selection is a mechanism that can produce the accumulating change over time that eventually leads to a new species. Many 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 abuse. This is a misunderstanding of the biological processes that lead up 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 and mutation. Origins of Humans Modern humans (Homo Sapiens) evolved from primates, a species of mammal species which includes gorillas and chimpanzees. The earliest human fossils prove that our ancestors were bipeds – walkers with two legs. Genetic and biological similarities show that we have an intimate relationship with the chimpanzees. In actual fact our closest relatives are the chimpanzees of the Pan genus. This includes pygmy as well as bonobos. The last common ancestor between humans and chimpanzees was between 8 and 6 million years old. In the course of time, humans have developed a variety of characteristics, including bipedalism and the use of fire. They also invented advanced tools. It is only within the last 100,000 years that we have developed the majority of our important characteristics. These include language, large brain, the ability to create and utilize complex tools, as well as the ability to adapt to cultural differences. Evolution happens when genetic changes allow individuals in a group to better adapt to their surroundings. This adaptation is driven by natural selection, a process that determines certain traits are favored over other traits. The ones who are better adapted are more likely to pass their genes on 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 says that species that share a common ancestor tend to develop similar characteristics over time. It is because these traits help them to reproduce and survive within their environment. All organisms possess an molecule called DNA that holds the information needed to control their growth. The structure of DNA is made of base pairs which are arranged in a spiral, around phosphate and sugar molecules. The sequence of bases within each strand determines the phenotype or the individual's unique appearance and behavior. Variations in a population are caused by reshufflings and mutations of genetic material (known collectively as alleles). Fossils from the early human species Homo erectus, as well as Homo neanderthalensis have been discovered in Africa, Asia and Europe. These fossils, despite differences in their appearance, all support the hypothesis that modern humans' ancestors originated in Africa. The genetic and fossil evidence suggests that early humans left Africa and moved to Asia and Europe.