The Berkeley Evolution Site
The Berkeley site has resources that can assist students and teachers learn about and teach evolution. The materials are arranged in optional learning paths, such as "What does T. rex look like?"
Charles Darwin's theory on natural selection explains how animals who are better equipped to adapt to changes in their environment survive over time and those who do not become extinct. Science is concerned with this process of biological evolution.
What is Evolution?
The term "evolution" could have many nonscientific meanings. For instance it could refer to "progress" and "descent with modifications." Scientifically it refers to a process of changing the characteristics of living organisms (or species) over time. This change is based in biological terms on natural selection and drift.
Evolution is a key principle in the field of biology today. It is an established theory that has stood up to the test of time and a multitude of scientific studies. In contrast to other theories in science like the Copernican theory or the germ theory of disease, the evolution theory does not address questions of religion 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 step-wise manner, over time. They called this 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 states that all species of organisms share a common ancestry, which can be proven through fossils and other lines of evidence. This is the current view on evolution, and is supported by a variety of disciplines, including molecular biology.
Scientists do not know how organisms have evolved however they are certain that natural selection and genetic drift are responsible for the evolution of life. Individuals with advantageous characteristics are more likely to live and reproduce. These individuals pass on their genes to the next generation. Over time, the gene pool gradually changes and develops into new species.
Some scientists use the term"evolution" in reference to large-scale changes, like the development of a species from an ancestral one. Certain scientists, such as population geneticists, define evolution in a broad sense, using the term "net change" to refer to the variation in the frequency of alleles over generations. Both definitions are accurate and acceptable,
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Click4R.Com) however certain scientists argue that allele frequency definitions miss important aspects of the 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 micro scale, for instance within cells.
The origin of life is one of the major topics in various disciplines, including biology, chemistry and geology. The origin of life is a subject of great interest in science, as it is a challenge to the theory of evolution. It is sometimes referred to "the mystery" of life or "abiogenesis."
Traditionally, the idea that life could emerge 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 an entirely natural process.
Many scientists still think it is possible to move from living to nonliving substances. The conditions needed to make life are not easy to replicate in a laboratory. This is why researchers investigating the beginnings of life are also interested in determining the physical properties of early Earth and other planets.
The growth of life is dependent on a number of complex chemical reactions which cannot be predicted by basic physical laws. These include the reading and re-reading of complex molecules, such as DNA or RNA, to produce proteins that serve a specific function. These chemical reactions can be compared to a chicken-and egg problem that is the emergence and growth of DNA/RNA, the protein-based cell machinery, is necessary to begin the process of becoming a living organism. Although without life, the chemistry that is required to create it does appear to work.
Abiogenesis research requires collaboration among scientists from different fields. This includes prebiotic chemists the astrobiologists,
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Evolutionary Changes
The term "evolution" is typically used today to describe the cumulative changes in the genetic characteristics of populations over time. These changes may result from the response to environmental pressures as discussed in the entry on Darwinism (see the entry on Charles Darwin for background), or from natural selection.
This process increases the number of genes that provide the advantage of survival for a species, resulting in an overall change in the appearance of a group. These evolutionary changes are caused by mutations, reshuffling of genes in the process of sexual reproduction, and also by the flow of genes.
While mutation and reshuffling of genes occur in all organisms and the process by which beneficial mutations are more prevalent is referred to as natural selection. This is because, as noted above those who have the beneficial trait tend to have a higher reproduction rate than those without it. This variation in the number of offspring born over many generations can cause a gradual change in the average number advantageous traits within a group.
A good example of this is the increase in the size of the beaks on different species of finches on the Galapagos Islands, which have developed different beak shapes to allow them to more easily access food in their new habitat. These changes in the shape and form of living organisms may also aid in the creation of new species.
The majority of the changes that occur are caused by one mutation, but occasionally several will happen at the same time. Most of these changes may be neutral or even harmful, but a small number can have a beneficial impact on survival and reproduction with increasing frequency over time. Natural selection is a mechanism that could result in the accumulation of changes over time that lead to the creation of a new species.
Some people confuse the notion of evolution with the notion that traits inherited can be changed through conscious choice or by use and abuse, a concept called soft inheritance. This is a misinterpretation of the biological processes that lead up to evolution. A more accurate description is that evolution is a two-step procedure which involves the separate and often antagonistic forces of natural selection and mutation.
Origins of Humans
Modern humans (Homo sapiens) evolved from primates - a group of mammals that also includes gorillas, chimpanzees, 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 our closest relatives are the chimpanzees of the Pan genus. This includes pygmy and bonobos. The last common ancestor of modern humans and chimpanzees was 8 to 6 million years old.
In the course of time, humans have developed a variety of traits, including bipedalism and the use of fire. They also invented advanced tools. It is only in the last 100,000 years or so that the majority of the important characteristics that differentiate us from other species have been developed.