The Berkeley Evolution Site
Teachers and students who visit the Berkeley site will find resources to assist them in understanding and teaching evolution. The resources are organized into optional learning paths such as "What did T. rex taste like?"
Charles Darwin's theory of natural selection describes how species who are better able to adapt biologically to a changing environment survive over time and those that do not disappear. Science is all about this process of biological evolution.
What is Evolution?
The term "evolution" can have many nonscientific meanings. For instance it could refer to "progress" and "descent with modifications." Scientifically it is a term used to describe a change in the characteristics of organisms (or species) over time. The reason for this change is biological terms on natural drift and selection.
Evolution is a key tenet in modern biology. It is an accepted theory that has stood up to the test of time and thousands of scientific studies. Evolution doesn't deal with God's presence or spiritual beliefs, unlike many other scientific theories such as the Copernican or germ theory of disease.
Early evolutionists like Erasmus Darwin (Charles’s grandfather) and Jean-Baptiste Lamarck believed that certain physical characteristics were predetermined to evolve in a step-like fashion over time. This was called the "Ladder of Nature" or scala Naturae. Charles Lyell first used this term in 1833 in his Principles of Geology.
Darwin published his theory of evolution in his book On the Origin of Species published in the early 1800s. It asserts that all species of organisms share an ancestry that can be traced by fossils and other evidence. This is the current view of evolution that is supported by many research lines in science which includes molecular genetics.
Scientists don't know how organisms have evolved, but they are confident that natural selection and genetic drift is the reason for the evolution of life. People with desirable traits are more likely to live and reproduce, and these individuals transmit their genes to the next generation. Over time, the gene pool gradually changes and evolves into new species.
Some scientists employ the term evolution in reference to large-scale changes, such the formation of an animal from an ancestral one. Some scientists, like population geneticists, define the term "evolution" in a broader sense by talking about the net change in the frequency of alleles across generations. Both definitions are correct and acceptable, however certain scientists argue that allele frequency definitions omit important features of evolutionary process.
Origins of Life
A key step in evolution is the development of life. This occurs when living systems begin to develop at the micro level, within individual cells, for example.
The origins of life are an important issue in a variety of areas that include biology and the field of chemistry. The origin of life is an area that is of immense interest to scientists, as it challenges the theory of evolution. It is sometimes referred to "the mystery" of life or "abiogenesis."
The idea that life could emerge from non-living objects was referred to as "spontaneous generation" or "spontaneous evolutionary". 에볼루션 카지노 was a common belief prior to Louis Pasteur's tests proved that the emergence of living organisms was not possible by the natural process.
Many scientists still believe it is possible to make the transition from nonliving substances to life. The conditions required to create life are difficult to reproduce in a lab. Researchers interested in the origins and evolution of life are also keen to know the physical properties of the early Earth as well as other planets.
Additionally, the evolution of life is the sequence of extremely complex chemical reactions that cannot be predicted based on basic physical laws on their own. This includes the conversion of long information-rich molecules (DNA or RNA) into proteins that carry out functions, and the replication of these complex molecules to generate new DNA or RNA sequences. These chemical reactions are often compared with the chicken-and-egg dilemma of how life first appeared with the development of DNA/RNA as well as proteins-based cell machinery is vital to the birth of life, but without the development of life, the chemical process that allows it is not working.
Research in the area of abiogenesis requires cooperation among scientists from a variety of disciplines. This includes prebiotic chemists the astrobiologists, the planet scientists geophysicists, geologists, and geophysicists.
Evolutionary Changes
The term "evolution" is typically used to refer to the accumulated changes in the genetic characteristics of populations over time. These changes could result from adaptation to environmental pressures, as described in the entry on Darwinism (see the entry on Charles Darwin for background) or natural selection.
This latter mechanism increases the frequency of genes that confer an advantage for survival in the species, leading to an overall change in the appearance of an entire group. These evolutionary changes are caused by mutations, reshuffling of genes in the process of sexual reproduction, and also by gene flow.
While mutation and reshuffling of genes happen in all living organisms, the process by which beneficial mutations become more common is known as natural selection. This is because, as mentioned above those with the advantageous trait are likely to have a higher reproduction rate than those without it. Over the course of several generations, this differential in the numbers of offspring produced can result in a gradual shift in the average number of beneficial characteristics in a particular population.
An excellent example is the growth of the size of the beaks on different species of finches in the Galapagos Islands, which have developed beaks with different shapes that allow them to easily access food in their new home. These changes in the form and shape of organisms can also help create new species.
Most of the changes that occur are the result of a single mutation, but occasionally several will happen at once. Most of these changes are neutral or even detrimental to the organism, however a small portion of them could be beneficial to the survival of the organism and its reproduction, thereby increasing the frequency of these changes in the population over time. Natural selection is a mechanism that causes the accumulating change over time that leads to the creation of a new species.
Some people confuse the idea of evolution with the notion that traits inherited can be altered by conscious choice or use and abuse, which is called soft inheritance. This is a misinterpretation of the biological processes that lead to evolution. It is more accurate to say that evolution is a two-step, independent process, which involves the forces of natural selection as well as mutation.
Origins of Humans
Humans of today (Homo Sapiens) evolved from primates, a group of mammal species that includes chimpanzees as well as gorillas. Our predecessors walked on two legs, as demonstrated by the first fossils. Genetic and biological similarities suggest that we are closely related to Chimpanzees. In reality we are the most closely related to the chimpanzees within the Pan genus, which includes pygmy chimpanzees and bonobos. The last common human ancestor and chimpanzees lived 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 is only in the last 100,000 years or so that most of the characteristics that differentiate us from other species have emerged. These include language, a large brain, the ability to build 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 their environment. This adaptation is triggered by natural selection, a process that determines certain traits are preferred over others. People with better 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 which have a common ancestor, tend to develop similar characteristics over time. This is because these traits allow them to survive and reproduce within their environment.
Every organism has an molecule called DNA that holds the information necessary to direct their growth. The DNA molecule is made up of base pairs that are spirally arranged around phosphate molecules and sugar molecules. The sequence of bases within each strand determines phenotype or the individual's unique appearance and behavior. The variations in a population are caused by mutations and reshufflings of genetic material (known collectively as alleles).
Fossils of the earliest human species, Homo erectus and Homo neanderthalensis were discovered in Africa, Asia, and Europe. While there are some differences between them the fossils all support the notion that modern humans first came into existence in Africa. The fossil evidence and genetic evidence suggest that early humans migrated from Africa into Asia and then Europe.