The Berkeley Evolution Site
Teachers and students who visit 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 that over time, animals that are more able to adapt to changing environments thrive, and those that don't become extinct. Science is about this process of biological evolutionary change.
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 change of traits over time in organisms or species. In biological terms, this change is caused by natural selection and genetic drift.
Evolution is a key concept in the field of biology today. It is a concept that has been verified by a myriad of scientific tests. Evolution does not deal with spiritual beliefs or God's presence, unlike many other theories of science, such as the Copernican or germ theory of diseases.
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 manner, 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.
In the early 1800s, Darwin formulated his theory of evolution and published it in his book On the Origin of Species. It states that all species of organisms have an ancestry that can be determined through fossils and other lines of evidence. This is the current understanding of evolution, and is supported by a variety of lines of research in science that include molecular genetics.
Scientists do not know how organisms evolved however they are certain that natural selection and genetic drift are the primary reason for the development of life. Individuals with advantageous traits are more likely to survive and reproduce, and they transmit their genes to the next generation. Over time the gene pool slowly changes and evolves into new species.
Some scientists employ the term"evolution" to refer to large-scale change, such as the development of one species from an ancestral one. Other scientists, such as population geneticists, define it more broadly by referring to the net change in the frequency of alleles across generations. Both definitions are accurate and acceptable, however some scientists argue that allele-frequency definitions omit important features of evolution.
Origins of Life
One of the most crucial steps in evolution is the appearance of life. This happens when living systems begin to develop at the micro level, within individual cells, for instance.
The origins of life are an issue in a variety of disciplines, including biology, chemistry, and geology. The question of how living things started has a special place in science due to it being an enormous challenge to the theory of evolution. It is sometimes referred to as "the mystery" of life or "abiogenesis."
The idea that life could emerge from non-living objects was referred to as "spontaneous generation" or "spontaneous evolutionary". It was a common belief prior to Louis Pasteur's tests showed that the emergence of living organisms was not possible through a natural process.
Many scientists believe that it is possible to go from nonliving materials to living. However, the conditions required are extremely difficult to reproduce in the laboratory. Researchers interested in the origins and evolution of life are also keen to learn about the physical characteristics of the early Earth as well as other planets.
Additionally, the evolution of life depends on a sequence of very complex chemical reactions that cannot be predicted based on basic physical laws alone. These include the reading and re-reading of complex molecules, such as DNA or RNA, to create proteins that perform a specific function. These chemical reactions can be compared with the chicken-and-egg issue which is the development and emergence of DNA/RNA, a protein-based cell machinery, is required for the beginning of life. Although without life, the chemistry required to enable it does appear to work.
Research in the field of abiogenesis requires collaboration among scientists from many different disciplines. This includes prebiotic scientists, astrobiologists and planetary scientists.
Evolutionary Changes
The word evolution is usually used to describe the accumulated changes in the genetic traits of an entire population over time. These changes may be the result of adapting to environmental pressures, as discussed in Darwinism.
This is a method that increases the frequency of genes in a species that confer an advantage in survival over other species and causes an ongoing change in the appearance of a group. These evolutionary changes are caused by mutations, reshuffling of genes during sexual reproduction, and the flow of genes.
Natural selection is the process that makes beneficial mutations more frequent. All organisms undergo mutations and reshuffles in their genes. As mentioned above, those with the beneficial trait have a higher reproduction rate than those who don't. Over the course of several generations, this differential in the number of offspring born can result in an inclination towards a shift in the average number of beneficial characteristics in a particular population.
One good example is the growing the size of the beaks 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 the shape and appearance of living organisms may also help create new species.
The majority of the changes that take place are caused by a single mutation, but occasionally, multiple mutations occur simultaneously. Most of these changes can be negative or even harmful however, a few could have a positive impact on survival and reproduce and increase their frequency over time. This is the mechanism of natural selection and it is able to eventually result in the gradual changes that ultimately lead to a new species.
Many people confuse the concept of evolution with the idea that inherited characteristics can be altered by conscious choice, or through use and abuse, a concept called 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 procedure which involves the separate and often antagonistic forces of mutation and natural selection.
Origins of Humans
Modern humans (Homo sapiens) evolved from primates - a group of mammals that also includes gorillas, chimpanzees, and bonobos. The earliest human fossils prove that our ancestors were bipeds. They were walkers with two legs. Biological and genetic similarities indicate that we have a close relationship with the chimpanzees. In fact, our closest relatives are chimpanzees from the Pan genus. This includes pygmy as well as bonobos. The last common ancestor of modern humans and chimpanzees was born between 8 and 6 million years ago.
Humans have evolved a wide range of traits throughout time such as bipedalism, use of fire, and the development of advanced tools. However, it is only in the last 100,000 years or so that the majority of the characteristics that differentiate us from other species have emerged. These include language, a large brain, the capacity to create and utilize complex tools, and cultural diversity.
Evolution occurs when genetic changes enable members of the group to better adapt to the environment. Natural selection is the mechanism that triggers this adaptation. Certain traits are preferred over others. The ones who are better adjusted are more likely to pass their genes on to the next generation. This is the way all species evolve and is the basis of the theory of evolution.
Scientists refer to it as the "law of Natural Selection." The law states species that have an ancestor in common will tend to develop similar characteristics in the course of time. This is because these traits allow them to live and reproduce in their environment.
Every living thing has an molecule called DNA that holds the information needed to guide their growth. visit this link consists of base pairs arranged spirally around phosphate molecules and sugar molecules. The sequence of bases within each strand determines phenotype, or the individual's characteristic appearance and behavior. Variations in mutations and reshuffling of the genetic material (known as alleles) during sexual reproduction can cause variation in a group.
Fossils from the earliest human species Homo erectus, as well as Homo neanderthalensis have been discovered in Africa, Asia and Europe. Despite some differences, these fossils all support the idea that modern humans first appeared in Africa. Genetic and fossil evidence also suggest that early humans came from Africa into Asia and then Europe.