The Berkeley Evolution Site
Teachers and students who browse the Berkeley site will find resources to aid in understanding and teaching evolution. The materials are organized into a variety of learning paths such as "What did T. rex taste like?"
Charles Darwin's theory of natural selection explains how over time, animals that are better able to adapt biologically to changing environments do better than those that don't become extinct. This process of evolution is what science is all about.
What is Evolution?
The term "evolution" could have a variety of meanings that are not scientific. For example, it can mean "progress" and "descent with modifications." Scientifically, it is a term used to describe a changing the characteristics of living organisms (or species) over time. The reason for this change is biological terms on natural drift and selection.
Evolution is a fundamental tenet in modern biology. 바카라 에볼루션 is a well-supported theory that has withstood the test of time and a multitude of scientific tests. It does not address spiritual beliefs or God's presence in the same way as other scientific theories 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 step-wise way, over time. This was referred to as the "Ladder of Nature" or 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 which was written in the early 1800s. It asserts that all species of organisms have an ancestry that can be traced by fossils and other evidence. This is the current view on evolution, which is supported in many areas of science, including molecular biology.
Scientists aren't sure the evolution of organisms but they are sure that natural selection and genetic drift is the primary reason for the evolution of life. People with traits that are advantageous are more likely to live and reproduce, and they pass their genes on to the next generation. In time this leads to a gradual accumulation of changes to the gene pool, which eventually lead to new species and forms.
Certain scientists use the term"evolution" in reference to large-scale change, such as the development of one species from an ancestral one. Other scientists, such as population geneticists, define the term "evolution" more broadly by referring the net change in allele frequencies over generations. Both definitions are valid and acceptable, however some scientists argue that allele-frequency definitions do not include important aspects of evolution.
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 subject in a variety of disciplines, including biology and chemical. The origin of life is a subject of great interest in science, as it challenges the theory of evolution. It is often referred to "the mystery" of life or "abiogenesis."
The notion that life could arise from non-living objects was referred to as "spontaneous generation" or "spontaneous evolutionary". It was a popular belief before Louis Pasteur's experiments proved that the development of living organisms was not achievable through a natural process.
Many scientists believe it is possible to go from nonliving to living substances. However, the conditions needed are extremely difficult to reproduce in the laboratory. Researchers studying the origins of life are also keen to understand the physical properties of the early Earth and other planets.
The life-cycle of a living organism is dependent on a number of complex chemical reactions, which cannot be predicted by simple physical laws. These include the reading of long, information-rich molecules (DNA or RNA) into proteins that carry out a function, and the replication of these intricate molecules to generate new DNA or sequences of RNA. These chemical reactions are often compared with the chicken-and-egg problem of how life began: The development of DNA/RNA as well as proteins-based cell machinery is vital to the birth of life, however, without the emergence of life the chemical reaction that is the basis for it is not working.
Abiogenesis research requires collaboration among scientists from various disciplines. This includes prebiotic scientists, astrobiologists and planetary scientists.
Evolutionary Changes
The term "evolution" is commonly used today to describe the cumulative changes in the genetic traits of populations over time. These changes could result from adaptation to environmental pressures, as discussed in the entry on Darwinism (see the entry on Charles Darwin for background), or from natural selection.
This mechanism also increases the frequency of genes that offer an advantage for survival in a species, resulting in an overall change in the appearance of a group. These evolutionary changes are caused by mutations, reshuffling of genes during sexual reproduction, and the flow of genes.
Natural selection is the process that makes beneficial mutations more common. All organisms undergo changes and reshuffles of genes. As mentioned above, those who possess the desirable characteristic have a higher reproduction rate than those who do not. Over many generations, this difference in the number of offspring born could result in an inclination towards a shift in the number of advantageous characteristics in a particular population.
One good example is the growth of beak size on different species of finches on the Galapagos Islands, which have evolved different shaped beaks to enable them to more easily access food in their new environment. These changes in shape and form can aid in the creation of new organisms.
The majority of changes are caused by one mutation, but sometimes several occur simultaneously. The majority of these changes are neither harmful nor even detrimental to the organism, however, a small proportion of them can have a positive impact on the longevity and reproduction of the species, thus increasing their frequency in the population over time. Natural selection is a process that could result in the accumulation of change over time that eventually leads to a new species.
Some people confuse the notion of evolution with the idea that the traits inherited from parents can be altered through conscious choice or by use and abuse, a notion known as soft inheritance. This is a misunderstood understanding of the nature of evolution and of the actual biological processes that trigger it. A more accurate description is that evolution involves a two-step process, that involves the distinct and often conflicting forces of natural selection and mutation.
Origins of Humans
Modern humans (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 on two legs. Genetic and biological similarities suggest that we are closely related to the chimpanzees. In actual fact our closest relatives are the chimpanzees from the Pan genus. This includes pygmy as well as bonobos. The last common ancestor of modern humans and chimpanzees lived between 8 and 6 million years ago.
Humans have developed a range of traits throughout time including bipedalism, the use of fire and advanced tools. But it's only in the past 100,000 years or so that most of the important traits that distinguish us from other species have developed. These include a big brain that is complex and the capacity of humans to build and use tools, and cultural diversity.
Evolution occurs when genetic changes enable members of an organization to better adapt to their environment. Natural selection is the mechanism that triggers this adaptation. Certain characteristics are more desirable than others. The more adjusted are more likely to pass on their genes to the next generation. This is the process that evolves all species, and it is the foundation of the theory of evolution.
Scientists call this the "law of natural selection." The law states that species that share an ancestor will tend to develop similar traits as time passes. This is because these traits make it easier to survive and reproduce within their environment.
Every organism has an molecule called DNA that holds the information necessary to direct their growth. The structure of DNA is made of base pairs arranged in a spiral around sugar and phosphate molecules. The sequence of bases within each strand determines phenotype which is the person's distinctive appearance and behavior. The variations in a population are caused by mutations and reshufflings 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. Although there are some differences the fossils all support the hypothesis that modern humans first appeared in Africa. The fossil evidence and genetic evidence suggest that early humans migrated out of Africa into Asia and then Europe.