The Berkeley Evolution Site
Teachers and students who browse the Berkeley site will find resources to help them understand and teach 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 that in time, creatures more adaptable to changing environments thrive, and those that don't become extinct. Science is all about this process of biological evolution.
What is Evolution?
The term "evolution" has a variety of nonscientific meanings. For instance "progress" or "descent with modification." Scientifically it is a term used to describe a change in the characteristics of organisms (or species) over time. This change is based in biological terms on natural selection and drift.
Evolution is one of the fundamental tenets of modern biology. It is an accepted theory that has stood the test of time and thousands of scientific experiments. Evolution does not deal with the existence of God or religious beliefs, unlike many other theories in science, like the Copernican or germ theory of diseases.
Early evolutionists, like Jean-Baptiste Lamarck and Erasmus Darwin (Charles's grandfather) believed that certain physical characteristics were predetermined to change in a step-like way, 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 states that all species of organisms have the same ancestry, which can be traced through fossils and other evidence. This is the current understanding of evolution, which is supported by numerous lines of research in science, including molecular genetics.
Although scientists aren't able to determine exactly how organisms evolved but they are certain that the evolution of life on earth is the result of natural selection and genetic drift. 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 results in gradual changes in the gene pool, which eventually lead to new species and forms.
Certain scientists use the term evolution in reference to large-scale changes, such the development of one species from an ancestral one. Certain scientists, including population geneticists, define evolution in a broader sense by using the term "net change" to refer to the change in the frequency of alleles across generations. Both definitions are accurate and acceptable, however some scientists argue that allele-frequency definitions miss important aspects of the evolutionary process.
Origins of Life
A key step in evolution is the appearance of life. This happens when living systems begin to develop at the micro level, within cells, for instance.
The origins of life are an important issue in many areas that include biology and the field of chemistry. The question of how living organisms began is of particular importance in science due to it being a major challenge to the theory of evolution. It is often described as "the mystery of life" or "abiogenesis."
The idea that life could emerge from non-living things was called "spontaneous generation" or "spontaneous evolutionary". It was a popular belief before Louis Pasteur's tests proved that the creation of living organisms was not achievable through the natural process.
Many scientists still believe that it is possible to go from nonliving substances to life. However, the conditions required are extremely difficult to reproduce in labs. 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 life-cycle of a living organism is dependent on a variety of complex chemical reactions which are not predicted by simple physical laws. These include the reading and re-reading of complex molecules, such as DNA or RNA, in order to make proteins that serve a specific function. These chemical reactions are often compared with the chicken-and-egg issue of how life first appeared: The emergence of DNA/RNA and protein-based cell machinery is essential to the birth of life, but without the development of life, the chemical reaction that is the basis for it does not appear to work.
Abiogenesis research requires collaboration among scientists from various fields. This includes prebiotic scientists, astrobiologists, and planetary scientists.
Evolutionary Changes
The word evolution is usually used today to refer to the accumulated changes in the genetic characteristics of an entire population over time. These changes may result from adaptation to environmental pressures as described in the entry on Darwinism (see the entry on Charles Darwin for background) or may result from natural selection.
This is a process that increases the frequency of those genes in a species which confer a survival advantage over others and causes gradual changes in the overall appearance of a population. These evolutionary changes are caused by mutations, reshuffling of genes during sexual reproduction and the flow of genes.
Natural selection is the process that allows beneficial mutations to become more common. All organisms undergo changes and reshuffles in their genes. This is because, as noted above those with the beneficial trait tend to have a higher fertility rate than those with it. 에볼루션 바카라 무료체험 in the number of offspring that are produced over many generations can cause a gradual change in the average number of beneficial traits in the group.
This can be seen in the evolution of various beak designs on finches that are found in the Galapagos Islands. They have developed these beaks in order that they can eat more quickly in their new home. These changes in shape and form could also help create new organisms.
Most of the changes that occur are caused by one mutation, but occasionally several will happen at once. The majority of these changes are neither harmful nor even detrimental to the organism, but a small percentage can have an advantageous impact on the longevity and reproduction of the species, thus increasing the frequency of these changes in the population over time. Natural selection is a mechanism that could result in the accumulation of change over time that leads to a new species.
Some people confuse the idea of evolution with the idea that traits inherited can be changed through conscious choice or use and abuse, which is known as soft inheritance. This is a misunderstanding of the biological processes that lead to the process of evolution. 에볼루션 바카라 무료 of evolution is that it is a two-step procedure involving the independent and often antagonistic forces of mutation and natural selection.
Origins of Humans
Modern humans (Homo sapiens) evolved from primates, a group of mammals that also includes chimpanzees and gorillas and bonobos. The earliest human fossils prove that our ancestors were bipeds - walkers on two legs. Genetic and biological similarities suggest that we are closely related to chimpanzees. In fact we are the most closely with chimpanzees in the Pan Genus, which includes bonobos and pygmy chimpanzees. The last common ancestor of modern humans and chimpanzees was between 8 and 6 million years old.
In the course of time, humans have developed a number of characteristics, such as bipedalism and the use fire. They also invented advanced tools. But it's only in the past 100,000 years or so that most of the characteristics that differentiate us from other species have emerged. These include language, large brain, the ability to create and utilize sophisticated tools, and a the ability to adapt to cultural differences.
Evolution happens when genetic changes allow members of a population to better adapt to their surroundings. This adaptation is triggered by natural selection, a process that determines certain traits are preferred over other traits. The ones with the best adaptations are more likely to pass on their genes to the next generation. This is the way all species evolve and is the foundation for the theory of evolution.
Scientists call it the "law of Natural Selection." The law states that species that share an ancestor will tend to develop similar characteristics over time. This is because those traits allow them to survive and reproduce in their environment.
All organisms have a DNA molecule, which provides the information necessary to guide their growth and development. The DNA molecule is made up of base pairs arranged spirally around sugar molecules and phosphate molecules. The sequence of bases in each string determines the phenotype or the distinctive appearance and behavior of an individual. Different mutations and reshufflings of the genetic material (known as alleles) during sexual reproduction cause variations in a population.
Fossils from the early human species Homo erectus, and Homo neanderthalensis have been found in Africa, Asia and Europe. Although there are some differences, these fossils all support the notion that modern humans first came into existence in Africa. Genetic and fossil evidence also suggest that early humans moved from Africa into Asia and then Europe.