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The Berkeley Evolution Site The Berkeley site offers resources that can help students and teachers understand and teach evolution. The materials are organized in different learning paths for example “What does T. rex look like?” Charles Darwin's theory of natural selection explains how animals who are better able to adapt to changes in their environment survive over time and those that don't disappear. This process of evolution in biology is the basis of science. What is Evolution? The term “evolution” could be used to refer to a variety of nonscientific meanings. For example it could refer to “progress” and “descent with modifications.” Scientifically it is a term used to describe a changing the characteristics of living things (or species) over time. The reason for this change is biological terms on natural drift and selection. Evolution is one of the fundamental tenets of modern biology. It is a concept that has been tested and proven by a myriad of scientific tests. It does not address the existence of God or religious beliefs like other theories of science, such as the Copernican or germ theory of diseases. Early evolutionists such as Erasmus Darwin (Charles’s grandfather) and Jean-Baptiste Lamarck believed that certain physical characteristics were predetermined to evolve in a stepped-like manner over time. This was known as the “Ladder of Nature” or scala Naturae. Charles Lyell first used this term in 1833 in his Principles of Geology. Darwin revealed his theory of evolution in his book On the Origin of Species published in the early 1800s. It states that all species of organisms share a common ancestry which can be traced using fossils and other evidence. This is the current understanding of evolution, which is supported by a variety of lines of research in science, including molecular genetics. Scientists don't know the evolution of organisms but they are sure that natural selection and genetic drift is responsible for the development of life. People with desirable traits are more likely to survive and reproduce, and these individuals transmit their genes to the next generation. Over time this leads to an accumulation of changes to the gene pool, which eventually result in new species and forms. Certain scientists use the term”evolution” to refer to large-scale changes, like the evolution of an animal from an ancestral one. Others, like population geneticists, define the term “evolution” more broadly by referring an overall change in allele frequencies over generations. Both definitions are acceptable and precise however, some scientists claim that the definition of allele frequency is lacking essential aspects of the evolution process. Origins of Life The development of life is a key stage in evolution. The beginning of life takes place when living systems begin to develop at a microscopic level, such as within individual cells. The origins of life are a topic in many disciplines, including geology, chemistry, biology and chemistry. The question of how living things started has a special place in science because it is an enormous challenge to the theory of evolution. It is often described as “the mystery of life,” or “abiogenesis.” see this that life could emerge from non-living things was called “spontaneous generation” or “spontaneous evolutionary”. This was a common belief prior to Louis Pasteur's tests proved that the creation of living organisms was not achievable through the natural process. Many scientists still believe it is possible to transition from nonliving substances to life. The conditions needed to create life are difficult to replicate in a laboratory. Researchers interested in the origins and development of life are also eager to know the physical properties of the early Earth as well as other planets. The growth of life is also dependent on a series of complex chemical reactions, which are not predicted by basic physical laws. These include the reading of long information-rich molecules (DNA or RNA) into proteins that perform functions as well as the replication of these intricate molecules to produce new DNA or RNA sequences. These chemical reactions are often compared with the chicken-and-egg problem of how life came into existence in the first place. The emergence of DNA/RNA and proteins-based cell machinery is vital to the birth of life, but without the appearance of life the chemical reaction that is the basis for it does not appear to work. Research in the field of abiogenesis requires collaboration between scientists from a variety of disciplines. This includes prebiotic chemists, astrobiologists, planetary scientists geophysicists and geologists. Evolutionary Changes The term “evolution” is used to describe gradual changes in genetic traits over time. These changes may result from the response to environmental pressures as described in the entry on Darwinism (see the entry on Charles Darwin for background), or from natural selection. This is a process that increases the frequency of genes in a species which confer an advantage in survival over others, resulting in an ongoing change in the appearance of a particular population. These evolutionary changes are caused by mutations, reshuffling genes during sexual reproduction and gene flow. Natural selection is the process that makes beneficial mutations more frequent. All organisms undergo changes and reshuffles of their genes. As previously mentioned, those with the beneficial trait have a higher reproduction rate than those that do not. Over the course of many generations, this variation in the numbers of offspring born could result in an inclination towards a shift in the average amount of desirable characteristics in a particular population. This is evident in the evolution of different beak shapes for finches from the Galapagos Islands. They have created these beaks to ensure they can get food more easily in their new habitat. These changes in shape and form could also help create new organisms. Most of the changes that take place are the result of a single mutation, but sometimes, several changes occur at once. The majority of these changes are not harmful or even harmful to the organism however a small portion of them could have an advantageous impact on survival and reproduction, thus increasing their frequency in the population over time. This is the process of natural selection, and it could eventually result in the accumulating changes that eventually result in an entirely new species. Some people confuse the notion of evolution with the notion that inherited characteristics can be changed through conscious choice or use and abuse, a concept known as soft inheritance. This is a misunderstanding of the nature of evolution and of the actual biological processes that lead to it. A more accurate description of evolution is that it is a two-step procedure which involves the separate, and often competing, forces of natural selection and mutation. Origins of Humans Modern humans (Homo Sapiens) evolved from primates, a group of mammal species that includes gorillas and chimpanzees. The earliest human fossils show that our ancestors were bipeds. They were walking on two legs. Genetic and biological similarities suggest that we share an intimate relationship with the chimpanzees. In actual fact our closest relatives are the chimpanzees from the Pan genus. This includes pygmy as well as bonobos. The last common human ancestor as well as chimpanzees lived between 8 and 6 million years ago. In the course of time, humans have developed a range of characteristics, such as bipedalism and the use fire. They also created advanced tools. It's only within the last 100,000 years that we have developed the majority of our essential characteristics. These include language, large brain, the ability to build and use complex tools, as well as the diversity of our culture. The process of evolution occurs when genetic changes enable members of the group to better adapt to the environment. This adaptation is triggered by natural selection, a process that determines certain traits are preferred over other traits. Those with the better adaptations are more likely to pass on their genes to the next generation. This is how all species evolve, and the foundation for the theory of evolution. Scientists refer to it as the “law of natural selection.” The law states species that have a common ancestor are likely to develop similar traits as time passes. It is because these traits help them to live and reproduce in their environment. Every living thing has a DNA molecule, which provides the information necessary to control their growth and development. The structure of DNA is composed of base pairs that are arranged in a spiral around phosphate and sugar molecules. The sequence of bases within each strand determines the phenotype which is the person's distinctive appearance and behavior. Variations in a population can be caused by mutations and reshufflings in genetic material (known collectively as alleles). Fossils from the earliest human species, Homo erectus and Homo neanderthalensis, have been found in Africa, Asia, and Europe. Despite some differences, these fossils all support the idea that modern humans first appeared in Africa. Evidence from fossils and genetics suggest that early humans came from Africa into Asia and then Europe.