The Berkeley Evolution Site
Students and teachers who explore the Berkeley site will find a wealth of resources to help them understand and teach evolution. The materials are organized into optional learning paths, such as "What did T. rex taste like?"
Charles Darwin's theory of natural selection explains how creatures that are better equipped to adapt to changes in their environment survive over time and those that do not become extinct. This process of evolution is what science is all about.
What is Evolution?
The word evolution has many nonscientific meanings, including "progress" or "descent with modification." Scientifically, it is a term used to describe a change in the characteristics of living things (or species) over time. This change is based in biological terms on natural drift and selection.
Evolution is an important tenet in modern biology. It is a theory that has been confirmed by a myriad of scientific tests. Contrary to other theories of science, such as the Copernican theory or the germ theory of disease, evolution does not address issues of spiritual 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 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, written in the early 1800s. It states that all species of organisms have a common ancestry, which can be determined through fossils and other lines of evidence. This is the modern view of evolution, which is supported by a variety of research lines in science that include molecular genetics.
While scientists do not know the exact mechanism by which organisms evolved but they are certain that the evolution of life on earth is the result of natural selection and genetic drift. People with advantages are more likely to live and reproduce. These individuals transmit their genes on to the next generation. As time passes the gene pool gradually changes and develops into new species.
Certain scientists use the term evolution in reference to large-scale changes, such the formation of one species from an ancestral one. Certain scientists, such as population geneticists define evolution in a broader sense by referring to the net change in allele frequency over generations. Both definitions are valid and acceptable, but some scientists believe that allele-frequency definitions do not include important aspects of evolution.
Origins of Life
The most important step in evolution is the emergence of life. The emergence of life occurs when living systems begin to develop at a micro scale, for instance within cells.
The origin of life is an important subject in many areas such as biology and the field of chemistry. The question of how living organisms began has a special place in science because it is an important challenge to the theory of evolution. It is sometimes referred to "the mystery" of life or "abiogenesis."
Traditionally, the idea that life could emerge from nonliving objects is known as spontaneous generation or "spontaneous evolution." This was a popular view before Louis Pasteur's experiments showed that it was impossible for the emergence of life to occur by a purely natural process.
Many scientists still believe it is possible to transition from nonliving substances to living. The conditions required to create life are difficult to reproduce in a lab. Researchers who are interested in the origins and development of life are also eager to learn about the physical characteristics of the early Earth as well as other planets.
Additionally, the evolution 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 the replication of complex molecules, like DNA or RNA, in order to make proteins that perform a particular function. These chemical reactions can be compared with the chicken-and-egg problem: the emergence and development of DNA/RNA, the protein-based cell machinery, is necessary to begin the process of becoming a living organism. Although without life, the chemistry needed to make it possible appears to be working.
Research in the field of abiogenesis requires collaboration between scientists from many different disciplines. This includes prebiotic chemists, astrobiologists, planetary scientists geophysicists and geologists.
Evolutionary Changes
The term "evolution" is typically used today to describe the accumulated changes in the genetic characteristics of populations over time. These changes may result from adaptation to environmental pressures, as described in the entry on Darwinism (see the entry on Charles Darwin for background), or from natural selection.
This process increases the frequency of genes that offer a survival advantage in a species, resulting in an overall change in the appearance of an entire group. These evolutionary changes are triggered by mutations, reshuffling of genes during sexual reproduction, and gene flow.
Natural selection is the process that makes beneficial mutations more frequent. All organisms undergo changes and reshuffles in their genes. As mentioned above, those with the beneficial trait have a higher reproductive rate than those who don't. Over the course of several generations, this variation in the numbers of offspring born could result in a gradual shift in the number of advantageous characteristics in a particular population.
A good example of this is the increase in beak size on different species of finches in the Galapagos Islands, which have evolved different shaped beaks to enable them to more easily access food in their new environment. These changes in form and shape can also aid in the creation of new species.
The majority of changes are caused by a single mutation, but sometimes several occur at once. The majority of these changes are not harmful or even harmful to the organism but a small percentage can have a positive impact on 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 could result in the accumulation of change over time that eventually leads to the creation of a new species.
Some people confuse the notion of evolution with the notion that inherited characteristics can be altered through conscious choice or use and abuse, a notion known as soft inheritance. This is a misunderstanding of the biological processes that lead up to the process of evolution. A more accurate description of evolution is that it is a two-step process that involves the distinct and often conflicting forces of mutation and natural selection.
Origins of Humans
Modern humans (Homo Sapiens) evolved from primates, a group of mammal species which includes chimpanzees and gorillas. Our ancestors walked on two legs, as shown by the earliest fossils. 무료에볼루션 and genetic similarities indicate that we have the same ancestry with the chimpanzees. In actual fact we are the closest connected to chimpanzees belonging to the Pan genus which includes bonobos and pygmy-chimpanzees. The last common ancestor shared between modern humans and chimpanzees dated between 8 and 6 million years old.
Humans have evolved a wide range of characteristics over time, including bipedalism, the use of fire and advanced tools. It's only within the last 100,000 years that we have developed the majority of our essential characteristics. They include a huge, complex brain, the ability of humans to construct and use tools, and cultural variety.
The process of evolution occurs when genetic changes allow members of the group to better adapt to their environment. This adaptation is triggered by natural selection, a process that determines certain traits are preferred over others. The better adjusted are more likely to pass on their genes to the next generation. 무료 에볼루션 is the way that all species evolve, and it is the basis of the theory of evolution.
Scientists call it the "law of Natural Selection." The law states that species which have a common ancestor are likely to develop similar characteristics in the course of time. It is because these traits allow them to live and reproduce in their environment.
Every living thing has a DNA molecule that contains the information needed to guide their growth. The structure of DNA is made of base pairs that are arranged in a spiral around phosphate and sugar molecules. The sequence of bases within each strand determines the phenotype which is the person's distinctive appearance and behavior. Different mutations and reshufflings of the genetic material (known as alleles) during reproduction causes variation in a group.
Fossils of the first human species, Homo erectus and Homo neanderthalensis were discovered in Africa, Asia, and Europe. Despite some differences they all support the hypothesis that modern humans first came into existence in Africa. The fossil and genetic evidence suggests that the first humans left Africa and migrated to Asia and Europe.