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The Berkeley Evolution Site Teachers and students who browse the Berkeley site will find resources to assist them in understanding and teaching evolution. The materials are arranged in various learning paths that can be used in a variety of ways, such as “What does T. rex look like?” Charles Darwin's theory of natural selection explains how over time creatures that are better able to adapt biologically to changing environments thrive, and those that do not become extinct. Science is concerned with this process of biological evolutionary change. What is Evolution? The term “evolution” has a variety of nonscientific meanings, including “progress” or “descent with modification.” Scientifically it refers to a process of changes in the traits of organisms (or species) over time. In biological terms the change is due to natural selection and genetic drift. Evolution is a central tenet of modern biology. It is a concept that has been tested and verified by thousands of scientific tests. Unlike many other scientific theories like the Copernican theory or the germ theory of disease, evolution does not address issues of spiritual belief or the existence of God. Early evolutionists, such as Jean-Baptiste Lamarck and Erasmus Darwin (Charles's grandfather), believed that certain physical traits were predetermined to change, in a gradual way, over time. This was referred to as the “Ladder of Nature” or scala Naturae. Charles Lyell first used this term in 1833 in his Principles of Geology. Darwin published 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 have common ancestors that can be traced by fossils and other evidence. This is the current understanding of evolution, which is supported by a variety of lines of scientific research that include molecular genetics. Scientists do not know how organisms have evolved however they are certain that natural selection and genetic drift is responsible for the development of life. Individuals with advantageous traits are more likely to survive and reproduce, and they pass their genes on to the next generation. As time passes, this results in gradual changes to the gene pool, which eventually lead to new species and types. Certain scientists also use the term evolution to refer to large-scale changes in evolutionary processes, such as the formation of a new species from an ancestral species. Other scientists, like population geneticists, define evolution more broadly by referring the net change in allele frequencies over generations. Both definitions are valid and reliable however some scientists believe that the definition of allele frequency is lacking important features of the evolutionary process. Origins of Life The emergence of life is an essential step in the process of evolution. The emergence of life occurs when living systems start to evolve at a micro level, such as within cells. The origins of life are a topic in many disciplines, including biology, chemistry and geology. The nature of life is a subject of great interest in science, as it is a challenge to the theory of evolution. It is often referred to as “the mystery of life,” or “abiogenesis.” The notion that life could arise from non-living things was called “spontaneous generation” or “spontaneous evolutionary”. It was a common belief prior to Louis Pasteur's tests proved that the creation of living organisms was not achievable through a natural process. Many scientists believe it is possible to go from living to nonliving substances. The conditions necessary to make life are not easy to reproduce in a lab. Researchers interested in the origins and evolution of life are also keen to learn about the physical characteristics of the early Earth as well as other planets. The growth of life is dependent on a number of complex chemical reactions, that are not predicted by simple physical laws. These include the reading and re-reading of complex molecules, such as DNA or RNA, to create proteins that perform a particular function. These chemical reactions can be compared with a chicken-and egg problem that is the emergence and growth of DNA/RNA, a protein-based cell machinery, is essential for the beginning of life. However, without life, the chemistry needed to make it possible appears to be working. Abiogenesis research requires collaboration among scientists from various disciplines. This includes prebiotic chemists, planet scientists, astrobiologists geophysicists and geologists. Evolutionary Changes The term “evolution” is typically used today to refer to the accumulated changes in genetic characteristics of a population over time. These changes could result from adaptation to environmental pressures as discussed in the entry on Darwinism (see the entry on Charles Darwin for background) or may result from natural selection. This is a method that increases the frequency of those genes which confer a survival advantage over others which results in gradual changes in the overall appearance of a population. These changes in evolutionary patterns are caused by mutations, reshuffling genes during sexual reproduction and gene flow. Natural selection is the process that makes beneficial mutations more common. All organisms undergo mutations and reshuffles in their genes. This is because, as mentioned above those with the advantageous trait are likely to have a higher reproduction rate than those with it. This difference in the number of offspring that are produced over a long period of time can result in a gradual change in the number of advantageous characteristics in the group. A good example of this is the growing beak size on various species of finches in the Galapagos Islands, which have developed different beak shapes that allow them to easily access food in their new environment. These changes in the form and shape of organisms can also be a catalyst for the creation of new species. The majority of changes are caused by one mutation, but sometimes several occur simultaneously. Most of these changes are neutral or even harmful to the organism, but a small percentage can have an advantageous impact on the longevity and reproduction of the species, thus increasing their frequency in the population over time. Natural selection is a mechanism that causes the accumulating changes over time that lead to a new species. Some people mistakenly associate evolution with the concept of soft inheritance which is the notion that inherited traits can be altered by deliberate choice or misuse. This is a misunderstanding of the biological processes that lead up to evolution. It is more accurate to say that evolution is a two-step independent process that involves the forces of natural selection as well as mutation. 에볼루션 슬롯게임 of Humans Humans of today (Homo sapiens) evolved from primates, a group of mammals that includes chimpanzees, gorillas, and bonobos. The earliest human fossils show that our ancestors were bipeds. They were walking on two legs. Genetic and biological similarities suggest that we are closely related to chimpanzees. In actual fact, we are most closely related to the chimpanzees within the Pan Genus, which includes bonobos and pygmy-chimpanzees. The last common ancestor shared between humans and chimpanzees was 8 to 6 million years old. Humans have evolved a variety of characteristics over time including bipedalism, the use of fire and advanced tools. But it's 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 create and utilize complex tools, as well as the diversity of our culture. The process of evolution occurs when genetic changes allow members of a population to better adapt to their surroundings. This adaptation is triggered by natural selection, which is a process by which certain traits are favored over others. The more adaptable 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 it as the “law of natural selection.” The law says that species that share a common ancestor tend to develop similar characteristics over time. This is because these traits make it easier to survive and reproduce within their environment. Every living thing has a DNA molecule, which contains the information needed to direct their growth and development. The DNA structure 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 a person. Variations in mutations and reshufflings of the genetic material (known as alleles) during sexual reproduction can cause variations in a population. Fossils of the earliest human species, Homo erectus and Homo neanderthalensis, have been found in Africa, Asia, and Europe. Despite some differences they all support the notion that modern humans first appeared in Africa. Evidence from fossils and genetics suggest that early humans moved out of Africa into Asia and then Europe.