The Berkeley Evolution Site
The Berkeley site offers resources that can help students and teachers learn about 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 states that in time, creatures more able to adapt to changing environments survive and those that do not become extinct. Science is about this process of biological evolution.
What is Evolution?
The word 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 changes in the traits of living things (or species) over time. This change is based in biological terms on natural selection and drift.
Evolution is a fundamental principle in modern biology. It is a theory that has been tested and proven by a myriad of scientific tests. Unlike many other scientific theories, such as the Copernican theory or the germ theory of disease, the evolution theory does not address questions of spiritual belief or God's existence.
Early evolutionists, like Jean-Baptiste Lamarck and Erasmus Darwin (Charles's grandfather) believed that certain physical characteristics were predetermined to change, in a step-wise way, over time. This was called the "Ladder of Nature" or scala Naturae. Charles Lyell used the term to describe this concept 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 different species of organisms share a common ancestry, which can be determined through fossils and other evidence. This is the modern view of evolution that is supported by numerous lines of research in science, including molecular genetics.
While scientists don't know the exact mechanism by which organisms evolved, they are confident that the evolution of life on earth is a result of natural selection and genetic drift. Individuals with advantageous characteristics are more likely than others to live and reproduce. They pass on their genes on to the next generation. In time, this results in a gradual accumulation of changes to the gene pool, which eventually lead to new species and types.
Certain scientists also use the term"evolution" to describe large-scale evolutionary changes like the creation of an entirely new species from an ancestral species. Certain scientists, such as population geneticists, define the term "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 valid and reliable however some scientists believe that the allele-frequency definition omits essential aspects of the evolution process.
에볼루션 블랙잭 of Life
A key step in evolution is the appearance of life. The beginning of life takes place when living systems start to develop at a microscopic level, like within cells.
The origins of life is an issue in a variety of disciplines such as biology, chemistry, and geology. The question of how living organisms began has a special place in science since it poses an important challenge to the theory of evolution. It is often referred to as "the mystery of life" or "abiogenesis."
The notion that life could emerge from non-living objects was referred to as "spontaneous generation" or "spontaneous evolutionary". It was a popular belief before Louis Pasteur's tests proved that the development of living organisms was not achievable through a natural process.
Many scientists still think it is possible to go from nonliving substances to living ones. However, the conditions required are extremely difficult to replicate in labs. Researchers investigating the nature of life are also interested in determining the physical properties of early Earth and other planets.
The development of life is dependent on a number of complex chemical reactions, which are not predicted by the basic physical laws. These include the reading and re-reading of complex molecules, like DNA or RNA, in order to make proteins that serve a specific function. These chemical reactions are comparable to the chicken-and-egg issue: the emergence and development of DNA/RNA, a protein-based cell machinery, is essential for the onset life. However, without life, the chemistry required to make it possible appears to be working.
Research in the field of abiogenesis requires cooperation among scientists from various disciplines. This includes prebiotic chemists, the astrobiologists, the planet scientists geophysicists and geologists.
Evolutionary Changes
The word evolution is usually used today to describe the accumulated changes in the genetic traits of a population over time. These changes may be the result of adaptation to environmental pressures as described in Darwinism.
This mechanism also increases the frequency of genes that confer the advantage of survival for an animal, resulting in an overall change in the appearance of the group. The specific mechanisms that cause these evolutionary changes include mutation and reshuffling of genes in sexual reproduction, and gene flow between populations.
Natural selection is the process that makes beneficial mutations more frequent. All organisms undergo changes and reshuffles of their genes. As previously mentioned, those who possess the desirable trait have a higher reproductive rate than those that do not. This differential in the number of offspring that are produced over a long period of time can cause a gradual change in the average number of beneficial traits within the group.
This is evident in the evolution of different beak designs on finches that are found in the Galapagos Islands. They have developed these beaks in order that they can access food more easily in their new habitat. These changes in the shape and form of organisms could also help create new species.
The majority of the changes that occur are the result of one mutation, but sometimes, several changes occur at once. Most of these changes are neither harmful nor even harmful to the organism but a small percentage can have a positive impact on survival and reproduction, thus increasing their frequency in the population over time. This is the way of natural selection, and it is able to, over time, produce the cumulative changes that eventually lead to the creation of a new species.
Some people mistakenly associate evolution with the concept of soft inheritance that is the belief that traits inherited from parents can be altered by deliberate choice or misuse. 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, involving the independent, and often competing, forces of mutation and natural selection.
Origins of Humans
Humans today (Homo sapiens) evolved from primates - a species of mammals that also includes chimpanzees, gorillas, and bonobos. The earliest human fossils indicate that our ancestors were bipeds - walkers with two legs. Genetic and biological similarities suggest that we are closely related to chimpanzees. In fact, we are most closely related to the chimpanzees within the Pan genus that includes pygmy and bonobos and pygmy chimpanzees. The last common ancestor of modern humans and chimpanzees lived between 8 and 6 million years ago.
In the course of time humans have developed a variety of characteristics, including bipedalism as well as the use of fire. They also created advanced tools. However, it is only in the last 100,000 years or so that the majority of the important characteristics that differentiate us from other species have emerged. These include language, a large brain, the capacity to build and use complex tools, and cultural diversity.
The process of evolution is when genetic changes allow members of the group to better adapt to the environment. This adaptation is driven by natural selection, a process whereby certain traits are favored over others. The more adjusted are more likely to pass on their genes to the next generation. This is the way all species evolve, and the basis for the theory of evolution.
Scientists call it the "law of natural selection." The law states that species which share a common ancestor tend to develop similar characteristics over time. This is because the traits make it easier for them to live and reproduce in their environments.
Every living thing has a DNA molecule, which contains the information needed to control their growth and development. The DNA molecule is made up of base pairs arranged spirally around phosphate molecules and sugar molecules. The sequence of bases within each strand determines the phenotype - the distinctive appearance and behavior of an individual. The variations in a population are caused by reshufflings and mutations of genetic material (known collectively as alleles).
Fossils from the earliest human species Homo erectus, as well as Homo neanderthalensis have been discovered in Africa, Asia and Europe. Although there are some differences, these fossils all support the notion that modern humans first appeared in Africa. The fossil and genetic evidence suggests that the first humans left Africa and migrated to Asia and Europe.