The Berkeley Evolution Site
Teachers and students who visit the Berkeley site will find resources to help them understand and teach evolution. The materials are arranged in optional learning paths like "What does T. rex look like?"
Charles Darwin's theory on natural selection explains how creatures who are better equipped to adapt biologically to changing environments survive longer and 에볼루션게이밍 those that do not end up becoming extinct. Science is all about this process of evolution.
What is Evolution?
The term "evolution" can have many nonscientific meanings, such as "progress" or "descent with modification." Scientifically it refers to a changes in the traits of organisms (or species) over time. This change is based in biological terms on natural selection and drift.
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. Evolution doesn't deal with the existence of God or religious beliefs like other theories of science, such as the Copernican or germ theory of diseases.
Early evolutionists, like Jean-Baptiste Lamarck and Erasmus Darwin (Charles's grandfather) believed that certain physical traits were predetermined to change, in a gradual manner, as time passes. 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 presented his theory of evolution in his book On the Origin of Species published in the early 1800s. It asserts that different species of organisms share the same ancestry, which can be proven through fossils and other lines of evidence. This is the current understanding of evolution that is supported by a variety of lines of research in science, including molecular genetics.
Scientists don't know how organisms evolved but they are sure that natural selection and genetic drift are the primary reason for the development of life. People with traits that are advantageous are more likely to live and reproduce, and these individuals transmit their genes to the next generation. Over time, this results in an accumulation of changes in the gene pool which gradually lead to new species and types.
Some scientists also use the term evolution to describe large-scale evolutionary changes like the creation of an entirely new species from an ancestral species. Certain scientists, such as population geneticists define evolution in a more broad sense by referring to the net change in allele frequency over generations. Both definitions are acceptable and accurate however some scientists believe that the allele-frequency definition is missing essential aspects of the evolution process.
Origins of Life
One of the most crucial steps in evolution is the appearance of life. The beginning of life takes place when living systems begin to develop at a microscopic level, such as within cells.
The origins of life are an important subject in a variety of areas, including biology and the field of chemistry. The nature of life is an area of interest in science because it challenges the theory of evolution. It is often called "the mystery of life," or "abiogenesis."
Traditionally, the belief that life can arise from nonliving things is known as spontaneous generation or "spontaneous evolution." This was a common belief before Louis Pasteur's experiments proved that it was impossible for the creation of life to occur by a purely natural process.
Many scientists believe it is possible to go from living to nonliving substances. The conditions required to make life are not easy to reproduce in a lab. This is why scientists investigating the beginnings of life are also keen to understand the physical properties of early Earth and other planets.
The growth of life is dependent on a variety of complex chemical reactions which are not predicted by simple physical laws. These include the reading and re-reading of complex molecules, such as DNA or RNA, in order to make proteins that serve a specific function. These chemical reactions can be compared with a chicken-and egg problem: the emergence and development of DNA/RNA, a protein-based cell machinery, is necessary for the onset life. However, without life, the chemistry required to create it does appear to work.
Research in the field of abiogenesis requires cooperation among scientists from various fields. This includes prebiotic chemists, planet scientists, astrobiologists, geologists and geophysicists.
Evolutionary Changes
The word evolution is usually used today to describe the cumulative changes in the genetic characteristics of an entire population over time. These changes can be the result of the adaptation to environmental pressures as described in Darwinism.
This is a process that increases the frequency of genes that confer a survival advantage over others, resulting in gradual changes in the appearance of a group. These evolutionary changes are triggered by mutations, reshuffling of genes during sexual reproduction and the flow of genes.
While mutation and reshuffling of genes occur in all organisms, the process by which beneficial mutations become more common is known as natural selection. As noted above, individuals with the beneficial trait have a higher reproduction rate than those that do not. Over the course of many generations, this difference in the number of offspring born can result in a gradual shift in the average amount of desirable characteristics in a particular population.
An excellent example is the growth of beak size on various species of finches in the Galapagos Islands, which have developed different beak shapes that allow them to easily access food in their new home. These changes in form and shape can also help create new organisms.
The majority of changes are caused by one mutation, however sometimes multiple occur simultaneously. Most of these changes may be harmful or neutral however, a few can have a beneficial impact on survival and reproduction, increasing their frequency as time passes. Natural selection is a mechanism that causes the accumulating change over time that leads to a new species.
Many people confuse the concept of evolution with the idea that the traits inherited from parents can be changed through conscious choice or by use and abuse, a concept called soft inheritance. This is a misunderstanding of the biological processes that lead to the process of evolution. A more accurate description is that evolution is a two-step procedure that involves the distinct and often antagonistic forces of natural selection and mutation.
Origins of Humans
Humans of today (Homo sapiens) evolved from primates, a group of mammals that also includes gorillas, chimpanzees, and bonobos. The earliest human fossils indicate that our ancestors were bipeds - walkers with two legs. Genetic and biological similarities show that we share a close relationship with Chimpanzees. In fact our closest relatives are chimpanzees belonging to the Pan genus. This includes pygmy and bonobos. The last common ancestor of modern humans and chimpanzees was between 8 and 6 million years ago.
Humans have developed a range of characteristics over time such as bipedalism, use of fire, and the development of advanced tools. However, it is only in the last 100,000 years or so that most of the essential characteristics that differentiate us from other species have emerged. These include language, large brain, the capacity to create and utilize sophisticated tools, and a the diversity of our culture.
Evolution occurs when genetic changes allow members of a group to better adapt to the environment. Natural selection is the process that drives this change. Certain characteristics are more desirable than others. The better adaptable are more likely to pass their genes on to the next generation. This is the process that evolves all species, and it is the basis of the theory of evolution.
Scientists refer to this as the "law of natural selection." The law states that species that share an ancestor will tend to develop similar characteristics as time passes. It is because these traits make it easier to survive and reproduce within their environment.
Every organism has the DNA molecule, which contains the information needed to control their growth. The DNA structure is made of base pairs that are arranged in a spiral around phosphate and sugar molecules. The sequence of bases within each strand determines phenotype which is the person's distinctive appearance and behavior. Different changes and reshuffling of genetic material (known as alleles) during sexual reproduction can cause variation in a group.
Fossils from the early human species Homo erectus, and Homo neanderthalensis have been discovered in Africa, Asia and Europe. These fossils, despite a few variations in their appearance, all support the idea of modern humans' origins in Africa. The fossil and genetic evidence suggests that the first humans left Africa and moved to Asia and Europe.