The Berkeley Evolution Site
Teachers and students who visit the Berkeley site will find resources to help them understand and teach evolution. The materials are arranged into different learning paths, such as "What did T. rex taste like?"
Charles Darwin's theory on natural selection describes how species that are better equipped to adapt biologically to changing environments over time, and those who do not become extinct. Science is concerned with this process of evolution.
What is Evolution?
The term "evolution" has a variety of nonscientific meanings, such as "progress" or "descent with modification." Scientifically, it refers to a change in the characteristics of living things (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 a concept that has been tested and verified by a myriad of scientific tests. Unlike many other scientific theories, such as the Copernican theory or the germ theory of disease, evolution is not a discussion of spiritual belief or the existence of God.
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 known as the "Ladder of Nature" or scala Naturae. Charles Lyell first used this term in 1833 in his Principles of Geology.
Darwin revealed his theory of evolution in his book On the Origin of Species published in the early 1800s. 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, and is supported by numerous lines of scientific research which includes molecular genetics.
Scientists aren't sure how organisms evolved, but they are confident that natural selection and genetic drift is the reason for the development of life. Individuals with advantageous traits are more likely to live and reproduce, and they pass their genes on to the next generation. Over time the gene pool gradually changes and develops into new species.
Some scientists also use the term evolution to refer to large-scale evolutionary changes like the creation of a new species from an ancestral species. Other scientists, like population geneticists, define the term "evolution" more broadly, referring to a net change in the frequency of alleles across generations. Both definitions are acceptable and accurate, although some scientists argue that the allele-frequency definition is missing crucial aspects of the evolutionary process.
Origins of Life
The development of life is a key stage in evolution. The emergence of life happens when living systems begin to develop at a micro level, like within individual cells.
The origin of life is an issue in a variety of disciplines, including biology, chemistry and geology. The origin of life is an area of great interest in science, as it is a challenge to the theory of evolution. It is often called "the mystery of life" or "abiogenesis."
Traditionally, the notion that life can emerge from nonliving things is known as spontaneous generation, or "spontaneous evolution." This was a popular belief prior to Louis Pasteur's experiments proved that it was impossible for the creation of life to happen through an entirely natural process.
Many scientists believe that it is possible to make the transition from nonliving substances to living. However, the conditions required are extremely difficult to replicate in a laboratory. This is why researchers investigating the nature of life are also keen to understand the physical properties of early Earth and other planets.
The growth of life is dependent on a variety of complex chemical reactions, which are not predicted by the basic physical laws. These include the reading of long information-rich molecules (DNA or RNA) into proteins that perform functions, and the replication of these intricate molecules to produce new DNA or sequences of RNA. These chemical reactions are often compared with the chicken-and-egg dilemma of how life came into existence: The appearance of DNA/RNA and protein-based cell machinery is essential to the birth of life, but without the development of life, the chemical process that allows it is not working.
Research in the area of abiogenesis requires collaboration between scientists from a variety of disciplines. This includes prebiotic chemists, planet scientists, astrobiologists, geologists and geophysicists.
Evolutionary Changes
The term "evolution" is commonly used today to describe the cumulative changes in genetic characteristics of a population over time. These changes can be the result of the adaptation to environmental pressures as described in Darwinism.
The latter is a mechanism that increases the frequency of genes which confer an advantage in survival over others, resulting in a gradual change in the overall appearance of a population. The specific mechanisms behind these evolutionary changes are mutation, reshuffling of genes during sexual reproduction, and also gene flow between populations.
Natural selection is the process that makes beneficial mutations more frequent. All organisms undergo changes and reshuffles of their genes. This occurs because, as we've mentioned earlier those who have the beneficial trait tend to have a higher reproductive rate than those without it. Over the course of several generations, this variation in the number of offspring born can result in gradual changes in the average number of advantageous characteristics in a particular population.
This is evident in the evolution of various beak designs on finches that are found in the Galapagos Islands. They have created these beaks to ensure they can get food more quickly in their new home. These changes in the shape and form of living organisms may also help create new species.
The majority of changes are caused by a single mutation, however sometimes multiple occur simultaneously. Most of these changes may be negative or even harmful however, a small percentage can have a beneficial impact on survival and reproduction with increasing frequency over time. This is the way of natural selection, and it could, over time, produce the cumulative changes that ultimately lead to the creation of a new species.
Some people confuse evolution with the idea of soft inheritance which is the notion that inherited traits can be changed by conscious choice or by abuse. This is a misunderstanding of the biological processes that lead to the process of evolution. A more accurate description is that evolution involves a two-step process, involving the independent, and often competing, forces of natural selection and mutation.
Origins of Humans
Modern humans (Homo sapiens) evolved from primates - a group of mammals that also includes chimpanzees, gorillas, and bonobos. The earliest human fossils indicate that our ancestors were bipeds - walkers on two legs. Biological and genetic similarities indicate that we have an intimate relationship with chimpanzees. In reality we are the closest 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 evolved a wide range of traits throughout time, including bipedalism, the use of fire and advanced tools. However, it is only in the past 100,000 years or so that the majority of the essential characteristics that differentiate us from other species have been developed. They include language, a large brain, the ability to build and use complex tools, as well as the diversity of our culture.
The process of evolution is when genetic changes allow members of an organization to better adapt to their environment. Natural selection is the mechanism that triggers this adaptation. Certain traits are preferred over others. The ones who are better adaptable are more likely to pass their genes on to the next generation. This is the way all species evolve, and the basis for the theory of evolution.
Scientists refer to it as the "law of Natural Selection." The law states that species that have an ancestor in common will tend to develop similar traits over time. This is because the characteristics make it easier for them to live and reproduce in their natural environment.
Every organism has an molecule called DNA that holds the information needed to control their growth. The DNA molecule consists of base pairs that are arranged in a spiral around sugar molecules and phosphate molecules. The sequence of bases found in each string determines the phenotype or the distinctive appearance and behavior of an individual. A variety of mutations and reshuffling of the genetic material (known as alleles) during reproduction causes variation in a group.
에볼루션게이밍 from the early human species Homo erectus and Homo neanderthalensis have been discovered in Africa, Asia and Europe. While there are some differences between them, these fossils all support the notion that modern humans first came into existence in Africa. Evidence from fossils and genetics suggest that early humans moved out of Africa into Asia and then Europe.