The Berkeley Evolution Site
Teachers and students who visit the Berkeley site will find resources to aid in understanding and teaching evolution. The materials are arranged into different learning paths such as "What did T. rex taste like?"
Charles Darwin's theory of natural selection states that over time, animals that are more adaptable to changing environments thrive, and those that do not become extinct. Science is all about the process of biological evolution.
What is Evolution?
The term "evolution" could have a variety of meanings that are not scientific. For example it could refer to "progress" and "descent with modifications." Scientifically it is a term used to describe a changing the characteristics of living things (or species) over time. In terms of biology, this change is based on natural selection and genetic drift.
Evolution is a key principle in modern biology. It is a theory that has been proven through thousands of scientific tests. Evolution doesn't deal with God's presence or spiritual beliefs like other theories in science, like the Copernican or germ theory of diseases.
Early evolutionists, such as Erasmus Darwin (Charles’s grandfather) and Jean-Baptiste Lamarck believed that certain physical traits were predetermined to change in a step-like fashion over time. They called this 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 which was written in the early 1800s. It asserts that all species of organisms share a common ancestry which can be traced by fossils and other evidence. This is the modern view of evolution that is supported by many research lines in science, including molecular genetics.
Scientists don't know how organisms evolved however they are certain that natural selection and genetic drift are the reason for the development of life. People with desirable traits are more likely to survive and reproduce, and they pass their genes on to the next generation. Over time the gene pool gradually changes and evolves into new species.
Some scientists use the term"evolution" to refer to large-scale change, such as the evolution of one species from an ancestral one. 에볼루션코리아 , such as population geneticists, define it more broadly, referring to the net change in the frequency of alleles across generations. Both definitions are valid and reliable however some scientists believe that the allele-frequency definition is missing important features of the evolutionary process.
Origins of Life
One of the most crucial steps in evolution is the development of life. This happens when living systems begin to develop at a micro-level - within individual cells, for example.
The origin of life is an issue in a variety of disciplines that include biology, chemistry, and geology. The nature of life is a topic that is of immense interest to scientists, as it challenges the theory of evolution. It is often referred to as "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". This was a popular belief before Louis Pasteur's tests proved that the development of living organisms was not possible 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 replicate in labs. Researchers who are interested in the origins and development of life are also eager to understand the physical properties of the early Earth as well as other planets.
The growth of life 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, like DNA or RNA, to produce proteins that perform a specific function. These chemical reactions can be compared with a chicken-and egg problem which is the development and emergence of DNA/RNA, protein-based cell machinery, is necessary to begin the process of becoming a living organism. However, without life, the chemistry that is required to enable it appears to be working.
Research in the field of abiogenesis requires collaboration between scientists from various disciplines. This includes prebiotic chemists, astrobiologists, planetary scientists geophysicists and geologists.
Evolutionary Changes
Today, the word evolution is used to describe the general changes in genetic traits over time. These changes can be the result of the adaptation to environmental pressures as discussed in Darwinism.
This is a method that increases the frequency of genes in a species that offer an advantage in survival over others which results in an ongoing change in the overall appearance of a population. The specific mechanisms behind these changes in evolutionary process include mutation and reshuffling of genes in sexual reproduction, and gene flow between populations.
Natural selection is the process that allows beneficial mutations to become more common. All organisms undergo changes and reshuffles of their genes. 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 differential in the numbers of offspring born can result in an inclination towards a shift in the amount of desirable characteristics in a particular population.
This can be seen in the evolution of different beak shapes for finches from the Galapagos Islands. They have developed these beaks in order that they can eat more easily in their new environment. These changes in form and shape can aid in the creation of new organisms.
The majority of changes are caused by one mutation, however sometimes multiple occur at the same time. Most of these changes are neither harmful nor even detrimental to the organism, however a small portion of them could have a positive impact on survival and reproduction, thus increasing their frequency in the population over time. This is the mechanism of natural selection and it could eventually result in the cumulative changes that eventually result in a new species.
Some people confuse the notion of evolution with the notion that the traits inherited from parents can be altered through conscious choice or by use and abuse, a notion called soft inheritance. This is a misinterpretation of the biological processes that lead up to evolution. It is more accurate to say that the process of evolution is a two-step, independent process, which involves the forces of natural selection as well as mutation.
Origins of Humans
Humans today (Homo sapiens) evolved from primates - a species of mammals that also includes gorillas, chimpanzees, and bonobos. The earliest human fossils indicate that our ancestors were bipeds - walkers with two legs. Genetic and biological similarities suggest that we share an intimate relationship with chimpanzees. In fact we are the closest related to the chimpanzees within the Pan Genus that includes pygmy and pygmy chimpanzees and bonobos. The last common ancestor shared between humans and chimpanzees was 8 to 6 million years old.
As time has passed, humans have developed a number of traits, including bipedalism and the use fire. They also created advanced tools. It's only in the last 100,000 years that we have developed the majority of our key characteristics. These include language, a large brain, the capacity to construct and use complex tools, and the diversity of our culture.
The process of evolution is when genetic changes allow members of the group to better adapt to the environment. Natural selection is the mechanism that drives this adaptation. Certain traits are preferred over others. People with better adaptations are more likely to pass on their genes to the next generation. This is the process that evolves all species, and it is the basis of the theory of evolution.
Scientists call this the "law of natural selection." The law states species that have a common ancestor are likely to develop similar characteristics over time. This is because those traits make it easier for them to survive and reproduce in their environment.
Every living thing has DNA molecules, which contains the information needed to direct their growth and development. The DNA molecule consists of base pairs that are spirally arranged around sugar molecules and phosphate molecules. The sequence of bases within each strand determines phenotype, or the individual's characteristic appearance and behavior. A variety of changes and reshuffling of genetic material (known as alleles) during sexual reproduction can cause variation in a group.
Fossils of the earliest human species, Homo erectus and Homo neanderthalensis, have been found in Africa, Asia, and Europe. These fossils, despite some differences in their appearance all support the hypothesis of the origins of modern humans in Africa. The evidence from fossils and genetics suggests that early humans left Africa and moved to Asia and Europe.