The Berkeley Evolution Site
Students and teachers who explore the Berkeley site will find a wealth of resources to aid in understanding and teaching evolution. The resources are organized into optional learning paths like "What does T. rex look like?"
Charles Darwin's theory of natural selection states that in time, creatures better able to adapt biologically to changing environments survive and those that do not become extinct. Science is concerned with this process of biological evolution.
What is Evolution?
The word evolution has many nonscientific meanings, such as "progress" or "descent with modification." It is scientifically based and refers to the process of changing traits over time in organisms or species. This change is based in biological terms on natural drift and selection.
Evolution is one of the fundamental tenets of modern biology. It is a concept that has been proven by thousands of scientific tests. In contrast to other theories in science, such as the Copernican theory or the germ theory of disease, evolution does not address issues of religion or the existence of God.
Early evolutionists such as Erasmus Darwin (Charles’s grandfather) and Jean-Baptiste Lamarck believed that certain physical characteristics were predetermined to evolve in a gradual manner over time. This was referred to as the "Ladder of Nature", or scala Naturae. Charles Lyell used the term to describe this idea in his Principles of Geology, first published in 1833.
Darwin revealed his theory of evolution in his book On the Origin of Species, written in the early 1800s. It asserts that all species of organisms share common ancestors that can be traced by fossils and other evidence. This is the current view on evolution, which is supported in a wide range of scientific fields, including molecular biology.
Although scientists aren't able to determine exactly how organisms developed however they are sure that the evolution of life on earth is the result of natural selection and genetic drift. People with desirable traits are more likely to live and reproduce, and they transmit their genes to the next generation. As time passes the gene pool gradually changes and develops into new species.
Some scientists employ the term"evolution" to refer to large-scale changes, such the formation of one species from an ancestral one. Other scientists, like population geneticists, define evolution more broadly by referring to a net change in allele frequencies over generations. Both definitions are acceptable and accurate however, some scientists claim that the definition of allele frequency is lacking crucial aspects of the evolutionary process.
Origins of Life
The emergence of life is a key step in evolution. This occurs when living systems begin to evolve at a micro-level - within cells, for example.
The origins of life are an important topic in a variety of disciplines that include biology and chemistry. The origin of life is an area that is of immense interest to scientists, as it is a challenge to the theory of evolution. It is sometimes referred to as "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 experiments proved that it was impossible for the development of life to occur by a purely natural process.
Many scientists still think it is possible to transition from nonliving substances to living ones. The conditions required to make life are not easy to replicate in a laboratory. 무료 에볼루션 investigating the beginnings of life are also interested in understanding the physical properties of early Earth and other planets.
The development of life is dependent on a variety of complex chemical reactions, which cannot be predicted by simple physical laws. These include the reading and re-reading of complex molecules, like DNA or RNA, to produce proteins that perform a specific function. These chemical reactions are comparable to the chicken-and-egg issue: the emergence and development of DNA/RNA, the protein-based cell machinery, is necessary for the onset life. However, without life, the chemistry needed to create it is working.
Abiogenesis research requires collaboration among scientists from different disciplines. This includes prebiotic chemists astrobiologists, planetary scientists, geologists and geophysicists.
Evolutionary Changes
Today, the word evolution is used to describe gradual changes in genetic traits over time. These changes could 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 latter mechanism increases the frequency of genes that provide a survival advantage in a species, resulting in an overall change in the appearance of a group. The specific mechanisms responsible for these evolutionary changes are mutation or reshuffling genes during sexual reproduction, and gene flow between populations.
Natural selection is the process that allows beneficial mutations to become more common. All organisms undergo mutations and reshuffles of their genes. As previously mentioned, those with the beneficial trait have a higher reproductive rate than those who do not. Over the course of many generations, this variation in the numbers of offspring born can result in gradual changes in the number of beneficial 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 that they can eat more easily in their new habitat. These changes in the form and shape of living organisms may also aid in the creation of new species.
Most of the changes that occur are the result of one mutation, however occasionally several will happen at the same time. Most of these changes may be negative or even harmful however, a small percentage may have a positive effect on survival and reproduce with increasing frequency as time passes. This is the way of natural selection, and it could, over time, produce the accumulating changes that ultimately lead to an entirely new species.
Some people confuse the notion of evolution with the notion that traits inherited can be altered by conscious choice, or through use and abuse, a concept known as soft inheritance. This is a misinterpretation of the biological processes that lead to evolution. A more accurate description is that evolution 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, which is a group of mammal species which includes chimpanzees as well as gorillas. Our ancestral ancestors were walking on two legs, as shown by the oldest fossils. Genetic and biological similarities suggest that we share the same ancestry with chimpanzees. In actual fact we are the most closely related to the chimpanzees within the Pan genus, which includes bonobos and pygmy chimpanzees. The last common ancestor between modern humans and chimpanzees dated between 8 and 6 million years old.
As time has passed humans have developed a range of characteristics, such as bipedalism and the use fire. They also developed advanced tools. But it's only in the past 100,000 years or so that most of the important characteristics that differentiate us from other species have been developed. They include a huge, complex brain human ability to build and use tools, and cultural diversity.
Evolution occurs when genetic changes allow members of a population to better adapt to their surroundings. This adaptation is driven by natural selection, which is a process by which certain traits are more desirable than other traits. The more adapted are more likely to pass their genes on to the next generation. This is the process that evolves all species and is the foundation of the theory of evolution.
Scientists call it the "law of natural selection." The law states that species which have a common ancestor are likely to develop similar traits as time passes. This is because those traits allow them to survive and reproduce in their natural environment.
All organisms have DNA molecules, which provides the information necessary to direct their growth and development. The DNA molecule is made up of base pairs arranged spirally around sugar molecules and phosphate molecules. The sequence of bases within each strand determines the phenotype, or the individual's characteristic appearance and behavior. A variety of 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 found in Africa, Asia, and Europe. These fossils, despite some variations in their appearance, all support the idea of modern humans' origins in Africa. The genetic and fossil evidence suggests that early humans left Africa and moved to Asia and Europe.