The Berkeley Evolution Site
The Berkeley site has resources that can help students and teachers to understand and teach about evolution. The resources are organized into optional learning paths for example "What does T. rex look like?"
Charles Darwin's theory of natural selection explains how over time creatures that are better able to adapt biologically to changing environments do better than those that don't become extinct. Science is concerned with this process of evolution.
What is Evolution?
The word evolution can be used to refer to a variety of nonscientific meanings. For example, it can mean "progress" and "descent with modifications." It is an academic term that refers to the process of changing characteristics over time in organisms or species. In biological terms this change is based on natural selection and genetic drift.
Evolution is one of the fundamental tenets of modern biology. It is a concept that has been tested and confirmed by thousands of scientific tests. In contrast to other theories in science such as the Copernican theory or the germ theory of disease, the evolution theory does not address questions of spiritual belief or the existence of God.
Early evolutionists, such as Erasmus Darwin (Charles’s grandfather) and Jean-Baptiste Lamarck believed that certain physical characteristics were predetermined to change in a stepped-like manner over time. This was referred to 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 claims that different species of organisms have a common ancestry, which can be traced through fossils and other evidence. This is the modern view of evolution that is supported by numerous lines of scientific research which includes molecular genetics.
While scientists don't know exactly how organisms developed however they are sure that the evolution of life on earth is a result of natural selection and genetic drift. People with desirable traits are more likely to survive and reproduce, and they transmit their genes to the next generation. As time passes, this results in gradual changes in the gene pool that gradually lead to new species and forms.
Certain scientists also use the term evolution to refer to large-scale evolutionary changes such as the creation of the new species from an ancestral species. Certain scientists, including population geneticists, define the term "evolution" in a more broad sense by using the term "net change" to refer to the change in allele frequency over generations. Both definitions are acceptable and accurate, although some scientists argue that the allele-frequency definition omits crucial aspects of the evolutionary process.
Origins of Life
One of the most crucial steps in evolution is the emergence of life. The emergence of life occurs when living systems start to develop at a micro level, like within cells.
The origins of life are a topic in many disciplines that include biology, chemistry, and geology. The question of how living things started has a special place in science because it is an enormous challenge to the theory of evolution. It is often described as "the mystery of life," or "abiogenesis."
Traditionally, the belief that life could emerge from nonliving objects is known as spontaneous generation, or "spontaneous evolution." This was a common belief before Louis Pasteur's experiments proved that it was impossible for the development of life to occur by an entirely natural process.
Many scientists believe that it is possible to transition from nonliving substances to living. However, the conditions that are required are extremely difficult to reproduce in a laboratory. This is why scientists studying the nature of life are also interested in understanding the physical properties of early Earth and other planets.
The development of life is also dependent on a series of complex chemical reactions, which cannot be predicted by simple physical laws. This includes the conversion of long, information-rich molecules (DNA or RNA) into proteins that carry out a function, and the replication of these intricate molecules to generate new DNA or sequences of RNA. These chemical reactions are comparable to the chicken-and-egg issue that is the emergence and growth of DNA/RNA, protein-based cell machinery, is essential for the beginning of life. However without life, the chemistry required to make it possible is working.
Research in the field of abiogenesis requires collaboration between scientists from many different fields. This includes prebiotic chemists, the astrobiologists, the planet scientists, geologists and geophysicists.
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 discussed in the entry on Darwinism (see the entry on Charles Darwin for background), or from natural selection.
This is a method that increases the frequency of genes in a species that confer an advantage in survival over others and causes a gradual change in the appearance of a population. These evolutionary changes are caused by mutations, reshuffling of genes in the process of sexual reproduction, and also by gene flow.
While reshuffling and mutation of genes are common in all living organisms The process through which beneficial mutations are more prevalent is called natural selection. This is because, as mentioned above those with the advantageous trait are likely to have a higher fertility 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 average number of beneficial traits in the group.
This can be seen in the evolution of various beak shapes for finches from the Galapagos Islands. They have developed these beaks so they can get food more easily in their new environment. These changes in the shape and appearance of organisms can also be a catalyst for the creation of new species.
Most of the changes that occur are the result of one mutation, however occasionally, multiple mutations occur simultaneously. The majority of these changes are not harmful or even detrimental to the organism, however a small portion of them could have a positive impact on survival and reproduction, thus increasing the frequency of these changes in the population over time. Natural selection is a mechanism that causes the accumulating change over time that eventually leads to the creation of a new species.
Many people confuse the concept of evolution with the idea that inherited characteristics can be altered by conscious choice or by use and abuse, which is called soft inheritance. This is a misinterpretation of the nature of evolution, and of the actual biological processes that lead to it. A more accurate description of evolution is that it is a two-step procedure involving the independent, and often competing, forces of mutation and natural selection.
Origins of Humans
Modern humans (Homo Sapiens) evolved from primates, which is a group of mammal species that includes chimpanzees as well as gorillas. The earliest human fossils show that our ancestors were bipeds. They were walking on two legs. Biological and genetic similarities indicate that we share an intimate relationship with chimpanzees. In fact our closest relatives are chimpanzees of the Pan genus. This includes pygmy, as well as bonobos. The last common human ancestor as well as chimpanzees was born between 8 and 6 million years ago.
discover here have evolved a wide range of traits over time, including bipedalism, the use of fire, and the development of advanced tools. It is only in the last 100,000 years or so that most of the essential traits that distinguish us from other species have emerged. They include a huge brain that is sophisticated, the ability of humans to build and use tools, as well as cultural diversity.
The process of evolution is when genetic changes allow members of an organization to better adapt to the environment. This adaptation is triggered by natural selection, a process that determines certain traits are more desirable than others. The more adapted are more likely to pass on their genes to the next generation. This is how all species evolve, and the basis of the theory of evolution.
Scientists refer to it as the "law of natural selection." The law states that species which have a common ancestor are likely to develop similar characteristics as time passes. This is because the characteristics make it easier for them to live and reproduce in their environment.
Every living thing has DNA molecules, which provides the information necessary to direct their growth and development. The DNA molecule consists of base pairs that are spirally arranged around phosphate molecules and sugar molecules. The sequence of bases within each strand determines phenotype which is the person's distinctive appearance and behavior. The variations in a population are caused by mutations and reshufflings of genetic material (known collectively as alleles).
Fossils of the first human species, Homo erectus and Homo neanderthalensis have been discovered in Africa, Asia, and Europe. These fossils, despite some variations in their appearance, all support the hypothesis of the origins of modern humans in Africa. The fossil evidence and genetic evidence suggest that early humans migrated from Africa into Asia and then Europe.