The Berkeley Evolution Site
The Berkeley site offers resources that can assist students and teachers learn about and teach evolution. The materials are organized into a variety of learning paths like "What did T. rex taste like?"
Charles Darwin's theory of natural selection describes how species who are better able to adapt to changes in their environments survive longer and those that don't become extinct. Science is concerned with this process of evolutionary change.
What is Evolution?
The term "evolution" can have a variety of meanings that are not scientific. For example, it can mean "progress" and "descent with modifications." Scientifically it refers to a process of changing the characteristics of living things (or species) over time. In biological terms the change is due to natural selection and genetic drift.
Evolution is a fundamental principle in modern biology. It is a theory that has been confirmed through thousands of scientific tests. In contrast to other theories in science like the Copernican theory or the germ theory of disease, the evolution theory is not a discussion of religious belief or God's existence.
Early evolutionists, such as Erasmus Darwin (Charles’s grandfather) and Jean-Baptiste Lamarck believed that certain physical traits were predetermined to change 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 concept in his Principles of Geology, first published in 1833.
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 a common ancestry which can be traced using fossils and other evidence. This is the current view of evolution, and is supported by numerous lines of scientific research, including molecular genetics.
Although scientists aren't able to determine exactly how organisms evolved however they are sure that the evolution of life on earth is the result of natural selection and genetic drift. Individuals with advantageous traits are more likely to live and reproduce, and these individuals pass their genes on to the next generation. As time passes the gene pool gradually changes and evolves into new species.
Some scientists employ the term"evolution" to refer to large-scale changes, like the evolution of one species from an ancestral one. Other scientists, such as population geneticists, define evolution more broadly by referring an overall change in allele frequencies over generations. Both definitions are acceptable and accurate however, some scientists claim that the allele-frequency definition is missing essential aspects of the evolution process.
Origins of Life
The emergence of life is a key step in evolution. The emergence of life occurs when living systems begin to develop at a microscopic level, such as within individual cells.
The origin of life is an important subject in a variety of areas such as biology and the field of chemistry. The question of how living things got their start has a special place in science due to it being an important challenge to the theory of evolution. It is often described as "the mystery of life" or "abiogenesis."
The idea that life could arise from non-living matter was known as "spontaneous generation" or "spontaneous evolutionary". This was a popular belief prior to Louis Pasteur's tests showed that the creation of living organisms was not possible by a 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 replicate in a laboratory. Researchers studying the origins of life are also interested in understanding the physical properties of the early Earth and other planets.
Furthermore, the growth of life is dependent on an intricate sequence of chemical reactions that can't be predicted from the fundamental physical laws on their own. These include the reading and replication of complex molecules, like DNA or RNA, to create proteins that perform a specific function. These chemical reactions are often compared with the chicken-and-egg dilemma of how life first appeared with the emergence of DNA/RNA and proteins-based cell machinery is vital to the birth of life, however, without the appearance of life the chemistry that makes it possible does not appear to work.
Abiogenesis research requires collaboration between scientists from various fields. This includes prebiotic scientists, astrobiologists, and planet scientists.
Evolutionary Changes
Today, the word evolution is used to describe the cumulative changes in genetic characteristics over time. These changes may result from adaptation to environmental pressures, as explained in the article on Darwinism (see the entry on Charles Darwin for background) or may result from natural selection.
The latter is a mechanism 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 particular population. The specific mechanisms that cause these evolutionary changes include mutation or reshuffling genes during sexual reproduction, and gene flow between populations.
Natural selection is the process that makes beneficial mutations more frequent. All organisms undergo mutations and reshuffles in their genes. 에볼루션 is because, as we've mentioned earlier those who have the beneficial trait tend to have a higher reproductive rate than those who do not have it. This differential in the number of offspring that are produced over a number of generations could result in a gradual change in the number of advantageous traits within a group.
An excellent example is the growing the size of the beaks on different species of finches on the Galapagos Islands, which have developed different beak shapes that allow them to easily access food 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 simultaneously. The majority of these changes are neither harmful nor even harmful to the organism however a small portion of them could be beneficial to survival and reproduction, thus increasing the frequency of these changes in the population over time. This is the process of natural selection and it is able to be a time-consuming process that produces the cumulative changes that eventually result in an entirely 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 known as soft inheritance. This is a misinterpretation of the biological processes that lead up to evolution. It is more precise 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 mammals that includes chimpanzees and gorillas and bonobos. The earliest human fossils show that our ancestors were bipeds - walkers with two legs. Genetic and biological similarities suggest that we are closely related to the chimpanzees. In fact, we are most closely related to the chimpanzees within the Pan genus which includes bonobos and pygmy-chimpanzees. The last common ancestor of humans and chimpanzees was 8 to 6 million years old.
Humans have developed a range of traits over time including bipedalism, the use of fire and advanced tools. It is only in the past 100,000 years or so that most of the essential traits that distinguish us from other species have been developed. These include a large brain that is sophisticated, the ability of humans to build and use tools, and the diversity of our culture.
Evolution occurs when genetic changes allow individuals of a population to better adapt to their environment. This adaptation is triggered by natural selection, which is a process by which certain traits are preferred over others. People with better adaptations are more likely to pass 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 species that have an ancestor in common will tend to acquire similar traits in the course of time. It is because these traits help them to reproduce and survive within their environment.
All organisms possess the DNA molecule, which contains the information needed to control their growth. The DNA molecule is composed of base pairs that are arranged in a spiral around phosphate molecules and sugar molecules. The sequence of bases within each strand determines the phenotype or the individual's unique appearance and behavior. 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. These fossils, despite some variations in their appearance, all support the theory that modern humans' ancestors originated in Africa. Evidence from fossils and genetics suggest that early humans moved out of Africa into Asia and then Europe.