The Berkeley Evolution Site Teachers and students who visit the Berkeley site will find resources to assist them in understanding and teaching evolution. The materials are arranged 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 equipped to adapt biologically to changing environment survive over time and those that don't disappear. This process of evolution in biology is the main focus of science. What is Evolution? The term "evolution" could have a variety of meanings that are not scientific. For example, it can mean "progress" and "descent with modifications." Scientifically, it refers to a process of changes in the traits of organisms (or species) over time. The reason for this change is biological terms on natural drift and selection. Evolution is an important concept in the field of biology today. It is an established theory that has withstood the test of time and thousands of scientific experiments. Evolution doesn't deal with the existence of God or religious beliefs, unlike many other theories of science, such as the Copernican or germ theory of diseases. Early evolutionists like Erasmus Darwin (Charles’s grandfather) and Jean-Baptiste Lamarck believed that certain physical traits were predetermined to change in a gradual manner 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 revealed his theory of evolution in his book On the Origin of Species published in the early 1800s. It claims that different species of organisms have an ancestry that can be traced through fossils and other lines of evidence. This is the modern view on evolution, and is supported in a wide range of disciplines that include molecular biology. Although scientists aren't able to determine the exact mechanism by which organisms evolved however they are sure that the evolution of life on earth is the result of natural selection and genetic drift. People with advantages are more likely than others to survive and reproduce. They transmit their genes to the next generation. Over time the gene pool gradually changes and evolves into new species. Some scientists also use the term"evolution" to refer to large-scale evolutionary changes such as the creation of an entirely new species from an ancestral species. Others, like population geneticists, define evolution more broadly by referring a net change in allele frequencies over generations. Both definitions are accurate and acceptable, however certain scientists argue that allele frequency definitions do not include important aspects of evolutionary process. Origins of Life The birth of life is a crucial step in the process of evolution. The emergence of life occurs when living systems begin to develop at a microscopic scale, for instance within cells. The origins of life are an important topic in a variety of areas that include biology and the field of chemistry. The origin of life is a subject of great interest in science because it challenges the theory of evolution. It is sometimes referred to "the mystery" of life or "abiogenesis." The idea that life could be born from non-living things was called "spontaneous generation" or "spontaneous evolutionary". It was a popular belief prior to Louis Pasteur's tests showed that the creation of living organisms was not possible by the natural process. Many scientists believe it is possible to go from living to nonliving substances. The conditions required to create life are difficult to replicate in a laboratory. Researchers investigating the nature of life are also interested in understanding the physical properties of the early Earth and other planets. The development of life is dependent on a variety of complex chemical reactions, which are not predicted by basic physical laws. These include the reading and re-reading of complex molecules, such as DNA or RNA, to create proteins that serve a specific function. These chemical reactions can be compared to the chicken-and-egg issue that is the emergence and growth of DNA/RNA, protein-based cell machinery, is essential to begin the process of becoming a living organism. However without life, the chemistry needed to make it possible does appear to work. Abiogenesis research requires collaboration among scientists from various disciplines. This includes prebiotic scientists, astrobiologists and planetary scientists. Evolutionary Changes Today, the word evolution is used to describe the gradual changes in genetic traits over time. These changes may be the result of adapting to environmental pressures, as explained in Darwinism. This is a process that increases the frequency of those genes that offer an advantage in survival over other species which results in a gradual change in the overall appearance of a population. The specific mechanisms that cause these evolutionary changes are mutation, reshuffling of genes during sexual reproduction, as well as gene flow between populations. Natural selection is the process that allows beneficial mutations to become more common. All organisms undergo changes and reshuffles of their genes. This is because, as mentioned above those with the beneficial trait tend to have a higher reproductive rate than those without it. This difference in the number of offspring born over a long period of time can result in a gradual change in the average number advantageous traits within a group. One good example is the increase in beak size on different species of finches in the Galapagos Islands, which have evolved different shaped beaks to enable them to more easily access food in their new home. These changes in shape and form can aid in the creation of new organisms. The majority of changes are caused by one mutation, however sometimes multiple occur at the same time. The majority of these changes could be neutral or even harmful, but a small number can have a beneficial impact on survival and reproduce, increasing their frequency as time passes. Natural selection is a mechanism that causes the accumulating change over time that leads to the creation of a new species. Many people confuse evolution with the idea of soft inheritance that is the belief that inherited traits can be changed by deliberate choice or misuse. This is a misinterpretation 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 involving the independent and often conflicting forces of mutation and natural selection. Origins of Humans Humans of today (Homo sapiens) evolved from primates - a species of mammals that includes chimpanzees, gorillas, and bonobos. The earliest human fossils prove that our ancestors were bipeds. They were walkers on two legs. Genetic and biological similarities suggest that we are closely related to chimpanzees. In fact we are the closest connected to chimpanzees belonging to the Pan Genus, which includes bonobos and pygmy chimpanzees. The last common ancestor of modern humans and chimpanzees lived between 8 and 6 million years ago. Over time humans have developed a variety of traits, including bipedalism and the use fire. They also created advanced tools. But it's only in the past 100,000 years or so that most of the important traits that distinguish us from other species have been developed. They include language, a large brain, the capacity to construct and use complex tools, as well as cultural diversity. The process of evolution occurs when genetic changes allow members of the group to better adapt to the environment. This adaptation is driven by natural selection, a process that determines certain traits are favored over others. The better adjusted are more likely to pass on their genes to the next generation. This is the way that all species evolve and is the basis of the theory of evolution. Scientists call it the "law of natural selection." The law states that species that have a common ancestor are likely to acquire similar traits in the course of time. It is because these traits allow them to survive and reproduce within their environment. Every organism has an molecule called DNA that holds the information needed to guide their growth. The structure of DNA is composed of base pairs which are arranged in a spiral, around sugar and phosphate molecules. The sequence of bases within each strand determines the phenotype or the individual's unique appearance and behavior. Variations in a population can be caused by mutations and reshufflings of genetic material (known collectively as alleles). Fossils of the earliest human species, Homo erectus and Homo neanderthalensis were discovered in Africa, Asia, and Europe. These fossils, despite some variations in their appearance, all support the idea of modern humans' origins in Africa. ???? ??? ?? fossil and genetic evidence suggests that the first humans left Africa and migrated to Asia and Europe.
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