The Berkeley Evolution Site
The Berkeley site offers resources that can help students and teachers understand and teach evolution. The materials are arranged into different learning paths like "What did T. rex taste like?"
Charles Darwin's theory of natural selection explains that in time, creatures more adaptable to changing environments thrive, and those that don't become extinct. This process of evolution is the main focus of science.
What is Evolution?
The word evolution can have many nonscientific meanings. For example, it can mean "progress" and "descent with modifications." It is an academic term that is used to describe the process of changing traits over time in organisms or species. In terms of biology this change is due to natural selection and genetic drift.
Evolution is a central tenet of modern biology. It is an accepted theory that has stood up to the tests of time and thousands of scientific studies. Evolution does not deal with the existence of God or religious beliefs, unlike many other theories of science, such as the Copernican or germ theory of disease.
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-like manner, as time passes. This was known as the "Ladder of Nature" or 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 states that all species of organisms have a common ancestry which can be traced by fossils and other evidence. This is the current perspective on evolution, which is supported in many scientific fields which include molecular biology.
Scientists don't know how organisms have evolved however they are certain that natural selection and genetic drift are the primary reason for the development of life. People with advantages are more likely than others to live and reproduce. These individuals transmit their genes on to the next generation. In time this leads to gradual changes to the gene pool, which eventually lead to new species and forms.
Certain scientists use the term"evolution" to refer to large-scale changes, such the development of an animal from an ancestral one. Read More Listed here , like population geneticists, define evolution more broadly by referring an overall change in allele frequencies over generations. Both definitions are accurate and acceptable, but some scientists believe that allele-frequency definitions omit important features of evolutionary process.
Origins of Life
The birth of life is a key step in evolution. This occurs when living systems begin to evolve at the micro level - within cells, for instance.
The origin of life is an important subject in many fields such as biology and the field of chemistry. The question of how living organisms began has a special place in science due to it being an important challenge to the theory of evolution. It is often referred to as "the mystery of life," or "abiogenesis."
The idea that life could be born from non-living matter was known as "spontaneous generation" or "spontaneous evolutionary". It was a popular belief before Louis Pasteur's experiments proved that the emergence of living organisms was not achievable through a natural process.
Many scientists believe that it is possible to make the transition from nonliving materials to living. However, the conditions needed are extremely difficult to replicate in a laboratory. Researchers who are interested in the evolution and origins of life are also eager to know the physical properties of the early Earth as well as other planets.
Additionally, the evolution of life is dependent on a sequence of very complex chemical reactions that cannot be predicted from basic physical laws on their own. These include the reading and re-reading of complex molecules, such as DNA or RNA, to create proteins that perform a particular function. These chemical reactions are often compared with the chicken-and-egg dilemma of how life first appeared in the first place. The appearance of DNA/RNA and protein-based cell machinery is essential for the onset of life, but without the appearance of life the chemistry that makes it possible isn't working.
Research in the field of abiogenesis requires collaboration among scientists from a variety of disciplines. This includes prebiotic scientists, astrobiologists and planetary scientists.
Evolutionary Changes
Today, the word evolution is used to describe the cumulative changes in genetic characteristics over time. These changes can result from adaptation to environmental pressures as discussed in the entry on Darwinism (see the entry on Charles Darwin for background) or natural selection.
The latter is a mechanism that increases the frequency of those genes in a species which confer a survival advantage over others which results in an ongoing change in the appearance of a population. The specific mechanisms responsible for these evolutionary changes include mutation, reshuffling of genes during sexual reproduction, and also gene flow between populations.
While mutation and reshuffling of genes are common in all organisms and the process by which beneficial mutations are more frequent is known as natural selection. This is because, as noted above those with the beneficial trait tend to have a higher fertility rate than those without it. This difference in the number of offspring that are produced over many generations can result in a gradual change in the average number of beneficial traits in the group.
One good example is the growth of beak size on various species of finches in the Galapagos Islands, which have evolved different shaped beaks to allow them to more easily access food in their new environment. These changes in shape and form can also help create new organisms.
The majority of the changes that take place are caused by one mutation, however occasionally several will happen simultaneously. Most of these changes can be neutral or even harmful however, a few can have a beneficial impact on survival and reproduction, increasing their frequency as time passes. Natural selection is a process that causes the accumulating changes over time that lead to a new species.
Some people confuse the notion of evolution with the idea that traits inherited can be altered through conscious choice or use and abuse, a notion known as soft inheritance. This is a misinterpretation of the biological processes that lead up to evolution. It is more accurate to say that evolution is a two-step independent process that involves the forces of natural selection and mutation.
Origins of Humans
Modern humans (Homo sapiens) evolved from primates - a species of mammals that also includes chimpanzees, gorillas, and bonobos. Our predecessors walked on two legs, as shown by the first fossils. Genetic and biological similarities suggest that we are closely related to the chimpanzees. In fact our closest relatives are chimpanzees belonging to the Pan genus. This includes pygmy as well as bonobos. The last common ancestor between humans and chimpanzees was between 8 and 6 million years old.
In the course of time humans have developed a variety of characteristics, including bipedalism and the use fire. They also developed advanced tools. However, it is only in the last 100,000 years or so that the majority of the essential traits that distinguish us from other species have been developed. These include language, large brain, the capacity to construct and use sophisticated tools, and a the diversity of our culture.
The process of evolution is when genetic changes allow members of a group to better adapt to the environment. Natural selection is the process that triggers this adaptation. Certain characteristics are more desirable than others. The ones with the best adaptations are more likely to pass their genes to the next generation. This is the way all species evolve, and the foundation for 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 over time. This is because the traits allow them to survive and reproduce in their environment.
All organisms have a DNA molecule, which provides the information necessary to control their growth and development. The DNA molecule consists of base pairs that are spirally arranged around phosphate molecules and sugar molecules. The sequence of bases within each strand determines the phenotype which is the person's distinctive appearance and behavior. The variations in a population are caused by mutations and reshufflings in genetic material (known collectively as alleles).
Fossils from the early human species Homo erectus, and Homo neanderthalensis have been discovered in Africa, Asia and Europe. While there are some differences between them the fossils all support the hypothesis that modern humans first appeared in Africa. Evidence from fossils and genetics suggest that early humans migrated out of Africa into Asia and then Europe.