The Berkeley Evolution Site
The Berkeley site contains resources that can assist students and teachers learn about and teach evolution. The materials are organized in different learning paths like "What does T. rex look like?"
Charles Darwin's theory of natural selection explains that over time, animals that are better able to adapt biologically to changing environments thrive, and those that are not extinct. This process of evolution is what science is all about.
What is Evolution?
The term "evolution" can have many nonscientific meanings, such as "progress" or "descent with modification." Scientifically, it refers to a process of changes in the traits of living things (or species) over time. This change is based in biological terms on natural drift and selection.
Evolution is one of the fundamental tenets of modern biology. It is a theory that has been confirmed through thousands of scientific tests. Evolution does not deal with the existence of God or religious beliefs, unlike many other scientific theories such as the Copernican or germ theory of disease.
Early evolutionists such as Erasmus Darwin (Charles’s grandfather) and Jean-Baptiste Lamarck believed that certain physical traits were predetermined to evolve in a gradual manner over time. They referred to this as the "Ladder of Nature" or the scala naturae. Charles Lyell used the term to describe this idea 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 share a common ancestry which can be traced using fossils and other evidence. This is the current understanding of evolution, and is supported by numerous research lines in science that include molecular genetics.
While scientists do not know 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. As time passes the gene pool slowly changes and evolves into new species.
Certain scientists also use the term"evolution" to describe large-scale evolutionary changes, such as the formation of the new species from an ancestral species. Some scientists, like population geneticists define evolution in a more broad sense by using the term "net change" to refer to the variation in the frequency of alleles over generations. Both definitions are correct and palatable, but certain scientists argue that allele frequency definitions omit important features of evolutionary process.
Origins of Life
One of the most crucial steps in evolution is the emergence of life. The beginning of life takes place when living systems begin to develop at a micro level, like within individual cells.
The origins of life are an important subject in a variety of disciplines that include biology and chemistry. The question of how living organisms began has a special place in science since it poses an enormous challenge to the theory of evolution. It is sometimes referred to as "the mystery" of life or "abiogenesis."
The idea that life could be born from non-living objects was referred to as "spontaneous generation" or "spontaneous evolutionary". It was a common belief prior to Louis Pasteur's tests showed 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 substances to life. The conditions needed for the creation of life are difficult to reproduce in a lab. This is why researchers studying the nature of life are also interested in determining the physical properties of early Earth and other planets.
The life-cycle of a living organism is also dependent on a series of complex chemical reactions that are not predicted by simple physical laws. These include the transformation of long information-rich molecules (DNA or RNA) into proteins that carry out functions and the replication of these intricate molecules to generate new DNA or sequences of RNA. These chemical reactions are often compared to the chicken-and-egg dilemma of how life began: The emergence of DNA/RNA and proteins-based cell machinery is vital for the beginning of life, but without the development of life the chemical reaction that is the basis for it is not working.
Research in the area of abiogenesis requires cooperation among scientists from various fields. This includes prebiotic scientists, astrobiologists, and planet scientists.
Evolutionary Changes
The term "evolution" today is used to describe the general changes in genetic traits 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 natural selection.
The latter is a mechanism that increases the frequency of genes which confer an advantage in survival over other species and causes an ongoing change in the overall appearance of a population. The specific mechanisms responsible for these changes in evolutionary process include mutation or reshuffling genes during sexual reproduction, as well as gene flow between populations.
While reshuffling and mutation of genes happen in all living organisms and the process by which beneficial mutations are more frequent 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 many generations, this difference in the numbers of offspring produced can result in an inclination towards a shift in the average number of advantageous traits in a population.
에볼루션 게이밍 is the growth of beak size on different species of finches found on the Galapagos Islands, which have developed beaks with different shapes that allow them to easily access food in their new home. These changes in form and shape can also help create new organisms.
The majority of the changes that occur are the result of a single mutation, but occasionally several will happen at the same time. Most of these changes are neutral or even harmful to the organism however, a small proportion of them can be beneficial to 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 causes the accumulating change over time that eventually leads to a new species.
Some people think that evolution is a form of soft inheritance which is the notion that inherited traits can be changed by deliberate choice or misuse. This is a misunderstanding of the biological processes that lead to evolution. It is more accurate to say that the process of evolution is a two-step, separate process, which involves the forces of natural selection and mutation.
Origins of Humans
Modern humans (Homo Sapiens) evolved from primates, a group of mammal species which includes chimpanzees as well as gorillas. The earliest human fossils indicate that our ancestors were bipeds. They were walking on two legs. Genetic and biological similarities show 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 lived between 8 and 6 million years ago.
As time has passed, humans have developed a number of traits, including bipedalism and the use fire. They also invented advanced tools. It is only in the past 100,000 years or so that most of the essential characteristics that differentiate us from other species have emerged. These include a large brain that is complex, the ability of humans to create and use tools, and the diversity of our culture.
Evolution occurs when genetic changes allow individuals of a population to better adapt to their surroundings. Natural selection is the process that drives this adaptation. Certain characteristics are more desirable than others. The ones who are better adapted are more likely to pass their genes on to the next generation. This is the way that all species evolve and is the basis of the theory of evolution.
Scientists refer to it as the "law of natural selection." The law states that species that have a common ancestor, tend to develop similar characteristics over time. This is because the characteristics make it easier for them to live and reproduce in their natural environment.
Every organism has DNA molecules, which is the source of information that helps direct their growth and development. The DNA molecule is composed of base pairs arranged spirally around sugar molecules and phosphate molecules. The sequence of bases within each strand determines the phenotype which is the person's distinctive appearance and behavior. Variations in a population are caused by mutations and reshufflings in genetic material (known collectively as alleles).
Fossils of the earliest human species, Homo erectus and Homo neanderthalensis were discovered in Africa, Asia, and Europe. These fossils, despite some differences in their appearance, all support the idea of modern humans' origins in Africa. The fossil and genetic evidence suggests that the first humans left Africa and moved to Asia and Europe.