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The Berkeley Evolution Site Teachers and students who visit the Berkeley site will find resources to aid in understanding and teaching evolution. The materials are organized in optional learning paths for example “What does T. rex look like?” Charles Darwin's theory on natural selection describes how species who are better equipped to adapt to changes in their environments survive longer and those that do not disappear. Science is all about this process of biological evolution. What is Evolution? The word evolution has many nonscientific meanings, including “progress” or “descent with modification.” Scientifically, it is a term used to describe a changing the characteristics of organisms (or species) over time. In biological terms this change is due to natural selection and genetic drift. Evolution is an important concept in modern biology. It is a theory that has been confirmed by a myriad of scientific tests. Unlike many other scientific theories, such as the Copernican theory or the germ theory of disease, evolution does not address issues of spiritual belief or God's existence. Early evolutionists, such as Erasmus Darwin (Charles’s grandfather) and Jean-Baptiste Lamarck believed that certain physical traits were predetermined to change in a stepped-like 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. In the early 1800s, Darwin formulated his theory of evolution and published it in his book On the Origin of Species. It states that all species of organisms share a common ancestry, which can be proven through fossils and other evidence. This is the current view of evolution, which is supported by numerous research lines in science which includes molecular genetics. Scientists aren't sure how organisms evolved however they are certain that natural selection and genetic drift is the primary reason for the development of life. Individuals with advantageous traits are more likely to live and reproduce, and they pass their genes on to the next generation. As time passes, the gene pool gradually changes and evolves into new species. Certain scientists use the term evolution in reference to large-scale changes, like the evolution of one species from an ancestral one. evolutionkr , like population geneticists, define it more broadly, referring to the net variation in the frequency of alleles over generations. Both definitions are accurate and acceptable, however some scientists believe that allele-frequency definitions omit important features of evolutionary process. Origins of Life The emergence of life is a key step in evolution. This occurs when living systems begin to develop at the micro level – within individual cells, for instance. The origins of life is a topic in many disciplines that include biology, chemistry and geology. The question of how living things got their start is a major topic in science due to it being a major challenge to the theory of evolution. It is often called “the mystery of life,” or “abiogenesis.” Traditionally, the notion that life can arise from nonliving objects is known as spontaneous generation or “spontaneous evolution.” This was a popular view before Louis Pasteur's research showed that it was impossible for the creation of life to happen through a purely natural process. Many scientists still believe that it is possible to transition from nonliving materials to living. The conditions required to make life are not easy to reproduce in a lab. This is why scientists 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 dependent on the sequence of extremely complex chemical reactions that can't be predicted based on basic physical laws on their own. These include the transformation of long, information-rich molecules (DNA or RNA) into proteins that carry out a function as well as the replication of these intricate molecules to create new DNA or sequences of RNA. These chemical reactions are comparable to a chicken-and egg problem: the emergence and development of DNA/RNA, a protein-based cell machinery, is necessary to begin the process of becoming a living organism. But, without life, the chemistry that is required to enable it appears to be working. Abiogenesis research requires collaboration among researchers from different disciplines. This includes prebiotic chemists, planet scientists, astrobiologists, geologists and geophysicists. Evolutionary Changes Today, the word evolution is used to describe the cumulative changes in genetic characteristics over time. These changes can be the result of the adaptation to environmental pressures as discussed in Darwinism. The latter is a mechanism that increases the frequency of those genes in a species that confer a survival advantage over others and causes an ongoing change in the appearance of a group. These changes in evolutionary patterns are caused by mutations, reshuffling genes in the process of sexual reproduction, and also by the flow of genes. Natural selection is the process that makes beneficial mutations more common. All organisms undergo changes and reshuffles in their genes. As noted above, individuals who have the advantageous trait have a higher reproduction rate than those who do not. This variation in the number of offspring produced over a long period of time can result in a gradual shift in the average number of beneficial traits within the group. A good example of this is the increase in the size of the beaks on different species of finches found on the Galapagos Islands, which have evolved different shaped beaks to allow them to more easily access food in their new home. These changes in the shape and form of organisms can also help create new species. The majority of changes are caused by one mutation, but sometimes several occur at once. The majority of these changes are not harmful or even detrimental to the organism, however a small portion of them could be beneficial to the survival of the organism and its reproduction, thereby increasing the frequency of these changes in the population over time. This is the way of natural selection and it could be a time-consuming process that produces the gradual changes that eventually result in the creation of a new species. Some people mistakenly associate evolution with the concept of soft inheritance which is the notion that traits inherited from parents can be changed by deliberate choice or misuse. This is a misinterpretation of the biological processes that lead to the process of evolution. A more accurate description of evolution is that it is a two-step process that involves the distinct and often conflicting forces of mutation and natural selection. Origins of Humans Humans of today (Homo Sapiens) evolved from primates, a group of mammal species that includes chimpanzees as well as gorillas. The earliest human fossils indicate that our ancestors were bipeds. They were walkers on two legs. Genetic and biological similarities suggest that we are closely related to Chimpanzees. In reality our closest relatives are the chimpanzees from the Pan genus. This includes pygmy, as well as bonobos. The last common human ancestor and chimpanzees was born between 8 and 6 million years ago. Humans have evolved a wide range of characteristics over time such as bipedalism, use of fire and advanced tools. However, it is only in the last 100,000 years or so that most of the essential traits that distinguish us from other species have developed. These include language, large brain, the ability to create and utilize complex tools, as well as the ability to adapt to cultural differences. Evolution is when genetic changes allow members of the group to better adapt to their environment. This adaptation is triggered by natural selection, a process whereby certain traits are more desirable than other traits. The ones with the best adaptations are more likely to pass their genes to the next generation. This is the process that evolves all species, and it is the foundation of the theory of evolution. Scientists call this the “law of natural selection.” The law states species that share an ancestor will tend to develop similar traits as time passes. This is because these traits allow them to live and reproduce in their environment. Every living thing has the DNA molecule, which contains the information necessary to direct their growth. The DNA structure is composed of base pair that are arranged in a spiral around sugar and phosphate molecules. The sequence of bases within each strand determines the phenotype which is the person's distinctive appearance and behavior. Variations in changes and reshuffling of genetic material (known as alleles) during sexual reproduction can cause variations in a population. Fossils of the first human species, Homo erectus and Homo neanderthalensis have been discovered in Africa, Asia, and Europe. Although there are some differences, these fossils all support the idea that modern humans first appeared in Africa. The fossil and genetic evidence suggests that early humans left Africa and migrated to Asia and Europe.