The Berkeley Evolution Site
Teachers and students who visit the Berkeley site will find resources to aid in understanding and teaching evolution. The resources are organized into different learning paths like "What does T. rex look like?"
Charles Darwin's theory on natural selection explains how animals who are better equipped to adapt biologically to changing environments survive longer and those that do not become extinct. This process of evolution is the main focus of science.
What is Evolution?
The term "evolution" could have a variety of meanings that are not scientific. For instance, it can mean "progress" and "descent with modifications." Scientifically it refers to a process of changing the characteristics of living things (or species) over time. This change is based in biological terms on natural drift and selection.
Evolution is the central tenet of modern biology. It is a well-supported theory that has stood up to the test of time and thousands of scientific tests. Unlike many other scientific theories such as the Copernican theory or the germ theory of disease, evolution does not address questions of religious belief or the existence of God.
Early evolutionists like Erasmus Darwin (Charles’s grandfather) and Jean-Baptiste Lamarck believed that certain physical traits were predetermined to evolve in a stepped-like manner over time. They referred to this as the "Ladder of Nature" or the scala naturae. Charles Lyell used the term to describe this concept in his Principles of Geology, first published in 1833.
In the early 1800s, Darwin formulated his theory of evolution and published it in his book On the Origin of Species. It asserts that all species of organisms have a common ancestry which can be traced by fossils and other evidence. This is the modern view on evolution, and is supported in a wide range of disciplines that include molecular biology.
Scientists aren't sure how organisms have evolved but they are sure that natural selection and genetic drift is the reason for the evolution of life. People with desirable traits are more likely than others to survive and reproduce. These individuals pass on their genes on to the next generation. As time passes, this results in an accumulation of changes in the gene pool, which eventually lead to new species and forms.
Some scientists also use the term"evolution" to describe large-scale evolutionary changes such as the creation of an entirely new species from an ancestral species. Other scientists, like population geneticists, define the term "evolution" more broadly by referring a net variation in the frequency of alleles over generations. Both definitions are valid and reliable however, some scientists claim that the allele-frequency definition is missing essential aspects of the evolution process.
Origins of Life
The emergence of life is a crucial step in evolution. This occurs when living systems begin to develop at a micro-level - within individual cells, for instance.
The origins of life are an important topic in many fields such as biology and chemistry. The nature of life is a subject of great interest in science, as it is a challenge to the theory of evolution. It is often described as "the mystery of life" or "abiogenesis."
The idea that life could arise from non-living objects was referred to as "spontaneous generation" or "spontaneous evolutionary". 에볼루션게이밍 was a popular belief prior to Louis Pasteur's tests showed that the emergence of living organisms was not achievable through a natural process.
Many scientists still think it is possible to move from nonliving substances to living ones. However, the conditions needed are extremely difficult to reproduce in the laboratory. Researchers interested in the origins and evolution of life are also eager to know the physical properties of the early Earth as well as other planets.
The development of life is dependent on a variety of complex chemical reactions which cannot be predicted by basic physical laws. 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 can be compared with the chicken-and-egg problem which is the development and emergence of DNA/RNA, the protein-based cell machinery, is necessary to begin the process of becoming a living organism. But, without life, the chemistry needed to enable it does appear to work.
Research in the area of abiogenesis requires cooperation among scientists from various disciplines. This includes prebiotic scientists, astrobiologists, and planet scientists.
Evolutionary Changes
The term "evolution" is used to describe general changes in genetic traits over time. These changes could result from the response to environmental pressures as described 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 confer an advantage for survival in a species, resulting in an overall change in the appearance of a group. These evolutionary changes are triggered by mutations, reshuffling of genes in the process of sexual reproduction, and also by gene flow.
While reshuffling and mutations of genes are common in all organisms and the process by which beneficial mutations are more prevalent is referred to as natural selection. As noted above, individuals with the beneficial characteristic have a higher reproduction rate than those who don't. Over the course of several generations, this difference in the numbers of offspring born can result in an inclination towards a shift in the average amount of desirable characteristics in a particular population.
This is evident in the evolution of different beak shapes for finches from the Galapagos Islands. They have developed these beaks so they can get food more easily in their new environment. These changes in the shape and appearance of living organisms may also aid in the creation of new species.
The majority of changes are caused by one mutation, although sometimes multiple occur at once. The majority of these changes could be neutral or even harmful however, a few could have a positive impact on the survival of the species and reproduce and increase their frequency over time. This is the mechanism of natural selection and it can eventually result in the cumulative changes that eventually lead to an entirely new species.
Some people confuse the idea of evolution with the notion that the traits inherited from parents can be altered through conscious choice or use and abuse, a concept known as soft inheritance. This is a misunderstanding of the biological processes that lead to evolution. It is more accurate to say that evolution is a two-step, independent process, that is influenced by the forces of natural selection and mutation.
Origins of Humans
Modern humans (Homo Sapiens) evolved from primates, which is a group of mammal species which includes gorillas and chimpanzees. The earliest human fossils indicate that our ancestors were bipeds, walking on two legs. Genetic and biological similarities suggest that we have an intimate relationship with the chimpanzees. In actual fact, our closest relatives are chimpanzees from the Pan genus. This includes pygmy, as well as bonobos. The last common human ancestor and chimpanzees was born between 8 and 6 million years ago.
Humans have evolved a variety of characteristics over time such as bipedalism, use of fire, and the development of advanced tools. It's only within the last 100,000 years that we've developed the majority of our essential traits. These include language, a large brain, the capacity to construct and use complex tools, and the ability to adapt to cultural differences.
The process of evolution occurs when genetic changes enable members of the group to better adapt to the environment. Natural selection is the mechanism that triggers this adaptation. Certain traits are preferred over others. The better adaptable are more likely to pass on their genes to the next generation. This is the process that evolves all species and forms the foundation of the theory of evolution.
Scientists refer to this as the "law of natural selection." The law states species that share an ancestor will tend to acquire similar traits over time. This is because the traits make it easier for them to survive and reproduce in their environments.
Every organism has an molecule called DNA that holds the information needed to control their growth. The structure of DNA is composed of base pair that are arranged in a spiral around phosphate 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 reshufflings and mutations of genetic material (known collectively as alleles).
Fossils from the earliest human species Homo erectus, and Homo neanderthalensis have been discovered in Africa, Asia and Europe. These fossils, despite some differences in their appearance all support the hypothesis that modern humans' ancestors originated in Africa. Evidence from fossils and genetics suggest that early humans migrated from Africa into Asia and then Europe.