The Berkeley Evolution Site
Students and teachers who explore the Berkeley site will find a wealth of resources to help them understand and teach 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 creatures who are better able to adapt to changes in their environment survive over time and those that don't end up becoming extinct. Science is about this process of evolutionary change.
What is Evolution?
The word evolution has many nonscientific meanings, including "progress" or "descent with modification." Scientifically it is a term used to describe a changes in the traits of living organisms (or species) over time. In terms of biology the change is caused by natural selection and genetic drift.
Evolution is an important concept in the field of biology today. It is a well-supported theory that has withstood the tests of time and thousands of scientific tests. Contrary to other theories of science, such as the Copernican theory or the germ theory of disease, the evolution theory does not address questions of religious belief or the existence of God.
Early evolutionists such as Erasmus Darwin (Charles’s grandfather) and Jean-Baptiste Lamarck believed that certain physical traits were predetermined to change in a step-like fashion 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.
In the early 1800s, Darwin formulated his theory of evolution and published it in his book On the Origin of Species. It asserts that different species of organisms have a common ancestry, which can be traced through fossils and other lines of evidence. This is the current perspective on evolution, and is supported by a variety of scientific fields that include molecular biology.
Although scientists aren't able to determine the exact mechanism by which organisms evolved but they are certain that the evolution of life on earth is the result of natural selection and genetic drift. People with desirable traits are more likely to survive and reproduce, and they pass their genes on to the next generation. Over time this leads to a gradual accumulation of changes in the gene pool which gradually result in new species and types.
Certain scientists use the term"evolution" to refer to large-scale changes, such the evolution of one species from an ancestral one. Other scientists, such as population geneticists, define it more broadly by referring a net variation in the frequency of alleles over generations. Both definitions are valid and acceptable, but certain scientists argue that allele frequency definitions miss important aspects of the evolution.
Origins of Life
The birth of life is a key step in the process of evolution. The emergence of life happens when living systems start to develop at a microscopic level, like within individual cells.
The origins of life are one of the major topics in various disciplines that include biology, chemistry, and geology. The question of how living organisms began has a special place in science because it is an enormous challenge to the theory of evolution. It is often referred to "the mystery" of life or "abiogenesis."
The notion that life could emerge from non-living matter was known as "spontaneous generation" or "spontaneous evolutionary". This was a popular belief prior to Louis Pasteur's tests proved that the creation of living organisms was not possible through a natural process.
Many scientists still believe that it is possible to make the transition from nonliving materials to living. However, the conditions needed are extremely difficult to replicate in the laboratory. This is why scientists investigating the origins of life are also interested in understanding the physical properties of the early Earth and other planets.
Additionally, the evolution of life depends on an intricate sequence of chemical reactions that can't be predicted from basic physical laws on their own. These include the reading and replication of complex molecules, such as DNA or RNA, in order to make proteins that perform a specific function. These chemical reactions are often compared with the chicken-and-egg issue of how life began with the appearance of DNA/RNA and protein-based cell machinery is essential for the onset of life, however, without the emergence of life the chemical reaction that is the basis for it is not working.
Research in the field of abiogenesis requires collaboration among scientists from various disciplines. This includes prebiotic scientists, astrobiologists, and planetary scientists.
Evolutionary Changes
The term "evolution" is used to describe the general changes in genetic traits over time. These changes may result from adaptation to environmental pressures as explained in the article on Darwinism (see the entry on Charles Darwin for background) or natural selection.
This latter mechanism increases the number of genes that offer the advantage of survival for the species, leading to an overall change in the appearance of an entire group. These evolutionary changes are triggered by mutations, reshuffling of genes in the process of sexual reproduction, and also by gene flow.
Natural selection is the process that makes beneficial mutations more frequent. All organisms undergo mutations and reshuffles of their genes. This occurs because, as mentioned above those with the advantageous trait are likely to have a higher reproduction rate than those who do not have it. This difference in the number of offspring produced over many generations can result in a gradual change in the number of advantageous traits in the group.
This is evident in the evolution of various beak designs on finches that are found in the Galapagos Islands. They have created these beaks to ensure that they can access food more quickly in their new home. These changes in the form and shape of organisms can also aid in the creation of new species.
The majority of the changes that occur are the result of one mutation, however occasionally several will happen simultaneously. Most of these changes can be neutral or even harmful however, a small percentage may have a positive effect on the survival of the species and reproduce, increasing their frequency over time. Natural selection is a mechanism that causes the accumulating changes over time that lead to the creation of a new species.
Some people mistakenly associate evolution with the concept of soft inheritance, which is the idea that inherited traits can be changed through deliberate choice or misuse. This is a misinterpretation of the nature of evolution and of the actual biological processes that cause it. A more accurate description of evolution is that it is a two-step process that involves the distinct, and often competing, forces of natural selection and mutation.
Origins of Humans
Modern humans (Homo Sapiens) evolved from primates, which is a group of mammal species that includes chimpanzees and gorillas. Our predecessors walked on two legs, as shown by the oldest fossils. Genetic and biological similarities suggest that we have an intimate relationship with the chimpanzees. In fact our closest relatives are the chimpanzees of the Pan genus. This includes pygmy and bonobos. The last common ancestor shared between humans and chimpanzees was between 8 and 6 million years old.
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 past 100,000 years or so that most of the important characteristics that differentiate us from other species have been developed. These include language, large brain, the capacity to construct and use complex tools, as well as the diversity of our culture.
Evolution occurs when genetic changes allow members of a population to better adapt to their environment. Natural selection is the mechanism that drives this change. Certain traits are preferred over others. People with better adaptations are more likely to pass their genes to the next generation. This is how all species evolve and forms the foundation of the theory of evolution.
Scientists call this the "law of natural selection." The law states that species which have a common ancestor, tend to develop similar traits over time. It is because these traits make it easier to reproduce and survive within their environment.
All organisms have a DNA molecule, which is the source of information that helps direct their growth and development. The structure of DNA is composed of base pairs that are arranged in a spiral around phosphate and sugar 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 in genetic material (known collectively as alleles).
Fossils of the first human species, Homo erectus and Homo neanderthalensis, have been found in Africa, Asia, and Europe. These fossils, despite a few variations in their appearance, all support the hypothesis of modern humans' origins in Africa. 에볼루션 슬롯게임 fossil and genetic evidence suggests that early humans left Africa and migrated to Asia and Europe.