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The Berkeley Evolution Site The Berkeley site contains resources that can help students and teachers understand and teach evolution. The materials are organized in different learning paths like “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 are not extinct. Science is all about this process of evolution. What is Evolution? The term “evolution” can have many nonscientific meanings, including “progress” or “descent with modification.” Scientifically, it refers to a process of changing the characteristics of organisms (or species) over time. In biological terms the change is caused by natural selection and genetic drift. Evolution is a key principle in the field of biology today. It is a well-supported theory that has stood up to the test of time and thousands of scientific studies. It does not address God's presence or spiritual beliefs in the same way as other theories in science, like the Copernican or germ theory of diseases. Early evolutionists, such as Jean-Baptiste Lamarck and Erasmus Darwin (Charles's grandfather), believed that certain physical characteristics were predetermined to change in a step-like way, over time. They referred to this as the “Ladder of Nature” or the 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 claims that different species of organisms have an ancestry that can be determined through fossils and other lines of evidence. This is the current view on evolution, and is supported in many scientific fields which include molecular biology. While scientists do not know exactly how organisms developed, they are confident that the evolution of life on earth is a result of natural selection and genetic drift. People with desirable traits are more likely to survive and reproduce, and these individuals pass their genes on to the next generation. In time, this results in gradual changes in the gene pool, which eventually lead to new species and types. Some scientists also use the term”evolution” to describe large-scale evolutionary changes like the creation of the new species from an ancestral species. Other scientists, such as population geneticists, define evolution more broadly, referring to an overall change in the frequency of alleles across generations. Both definitions are accurate and palatable, but some scientists argue that allele-frequency definitions do not include important aspects of evolution. Origins of Life The most important step in evolution is the appearance of life. The emergence of life occurs when living systems start to evolve at a micro level, such as within cells. The origin of life is one of the major topics in various disciplines, including biology, chemistry, and geology. The nature of life is an area of great interest in science because it is a challenge to the theory of evolution. It is often referred to “the mystery” of life or “abiogenesis.” Traditionally, the idea that life can emerge from nonliving objects is known as spontaneous generation, or “spontaneous evolution.” This was a popular view before Louis Pasteur's experiments showed that it was impossible for the creation of life to be a result of the natural process. Many scientists believe it is possible to transition from living to nonliving substances. However, the conditions required are extremely difficult to reproduce in a laboratory. Researchers interested in the origins and development of life are also eager to understand the physical properties of the early Earth as well as other planets. Furthermore, the growth of life is a sequence of very complex chemical reactions that cannot be predicted from the fundamental physical laws on their own. These include the reading and the replication of complex molecules, such as DNA or RNA, to produce proteins that serve a specific function. These chemical reactions are often compared to the chicken-and-egg issue of how life began: The development of DNA/RNA as well as protein-based cell machinery is essential to the birth of life, but without the development of life the chemical process that allows it is not working. Abiogenesis research requires collaboration among researchers from different disciplines. This includes prebiotic chemists, astrobiologists, planetary scientists, geologists and geophysicists. Evolutionary Changes The term “evolution” is used to describe the cumulative changes in genetic characteristics over time. These changes may be the result of adapting to environmental pressures, as discussed in Darwinism. This mechanism also increases the frequency of genes that confer the advantage of survival for the species, leading to an overall change in the appearance of an entire group. These evolutionary changes are caused by mutations, reshuffling genes during sexual reproduction and gene flow. While reshuffling and mutations of genes are common in all organisms and the process by which beneficial mutations are more frequent is referred to as natural selection. This happens because, as mentioned above, those individuals with the beneficial trait tend to have a higher fertility rate than those without it. Over the course of several generations, this difference in the number of offspring produced can result in gradual changes in the average number of beneficial traits in a population. A good example of this is the growing the size of the beaks on different species of finches in the Galapagos Islands, which have developed beaks with different shapes to allow them to more easily access food in their new environment. These changes in shape and form can aid in the creation of new organisms. The majority of changes are caused by one mutation, but sometimes several occur at once. Most of these changes are not harmful or even harmful to the organism however a small portion of them could have an advantageous impact on 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 can eventually result in the cumulative changes that eventually lead to a new species. Many people confuse the concept of evolution with the idea that traits inherited can be changed through conscious choice, or through use and abuse, which is called soft inheritance. This is a misunderstanding of the biological processes that lead up to evolution. A more accurate description of evolution is that it involves a two-step process, involving the independent and often conflicting forces of natural selection and mutation. Origins of Humans Humans of today (Homo sapiens) evolved from primates – a species of mammals that also includes chimpanzees and gorillas and bonobos. Our predecessors walked on two legs, as evidenced by the oldest fossils. Genetic and biological similarities suggest that we have an intimate relationship with the chimpanzees. In fact our closest relatives are chimpanzees from the Pan genus. This includes pygmy and bonobos. The last common human ancestor as well as chimpanzees was born between 8 and 6 million years ago. In the course of time humans have developed a number 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. They include language, a large brain, the ability to create and utilize complex tools, as well as the ability to adapt to cultural differences. click through the next site 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 preferred over other traits. People with better adaptations are more likely to pass their genes to the next generation. This is the way that all species evolve and forms the basis of the theory of evolution. Scientists refer to this as the “law of natural selection.” The law states that species that have an ancestor in common will tend to develop similar characteristics as time passes. This is because these traits help them to survive and reproduce within their environment. All organisms have a DNA molecule that contains the information needed to control their growth and development. The DNA molecule is made up of base pairs that are spirally arranged around sugar molecules and phosphate molecules. The sequence of bases in each string determines the phenotype or the appearance and behavior of a person. The variations in a population are caused by mutations and reshufflings of genetic material (known collectively as alleles). Fossils from the early human species Homo erectus, as well as Homo neanderthalensis have been found in Africa, Asia and Europe. Although there are some differences, these fossils all support the notion that modern humans first appeared in Africa. The evidence from fossils and genetics suggests that early humans left Africa and moved to Asia and Europe.