The Berkeley Evolution Site
The Berkeley site offers resources that can help students and teachers learn about and teach evolution. The materials are organized in various learning paths that can be used in a variety of ways 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 survive and those that are not extinct. This process of evolution in biology is what science is all about.
What is Evolution?
The term "evolution" could have many nonscientific meanings. For instance, it can mean "progress" and "descent with modifications." It is a scientific term that refers to the process of change of traits over time in organisms or species. This change is based in biological terms on natural selection and drift.
Evolution is the central tenet of modern biology. It is a well-supported theory that has stood the tests of time and thousands of scientific tests. Unlike many other scientific theories, such as the Copernican theory or the germ theory of disease, evolution does not address issues of religious 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.
In the early 1800s, Darwin formulated his theory of evolution and published it in his book On the Origin of Species. It claims that different species of organisms have the same ancestry, which can be proven through fossils and other evidence. This is the modern view of evolution, and is supported by numerous lines of research in science which includes molecular genetics.
Scientists aren't sure the evolution of organisms but they are sure that natural selection and genetic drift are the primary reason for the development of life. People with desirable traits are more likely to survive and reproduce. They transmit their genes on to the next generation. As time passes, the gene pool gradually changes and develops into new species.
Certain scientists also use the term"evolution" to describe large-scale evolutionary changes such as the creation of an entirely new species from an ancestral species. Some scientists, like population geneticists, define evolution in a more broad sense by talking about the net variation in the frequency of alleles over generations. Both definitions are valid and reliable, although some scientists argue that the definition of allele frequency is lacking crucial aspects of the evolutionary process.
Origins of Life
The emergence of life is a crucial stage in evolution. This happens when living systems begin to evolve at a micro-level - within individual cells, for instance.
The origin of life is one of the major topics in various disciplines such as biology, chemistry and geology. The question of how living things started is a major topic in science because it is an important challenge to the theory of evolution. It is often called "the mystery of life," or "abiogenesis."
The idea that life could arise from non-living matter was known as "spontaneous generation" or "spontaneous evolutionary". It was a common belief prior to Louis Pasteur's experiments proved that the creation of living organisms was not possible through an organic process.
Many scientists believe that it is possible to transition from nonliving substances to life. The conditions necessary to make life are not easy to reproduce in a lab. Researchers who are interested in the origins and development of life are also eager to understand the physical properties of the early Earth as well as other planets.
The development of life is dependent on a variety of complex chemical reactions which are not predicted by basic physical laws. These include the reading of long, information-rich molecules (DNA or RNA) into proteins that carry out some function and the replication of these intricate molecules to generate new DNA or sequences of RNA. These chemical reactions are often compared to the chicken-and-egg dilemma of how life came into existence with the appearance of DNA/RNA and protein-based cell machinery is crucial for the onset of life, but without the emergence of life the chemical process that allows it does not appear to work.
Abiogenesis research requires collaboration between researchers from different fields. This includes prebiotic scientists, astrobiologists and planetary scientists.
Evolutionary Changes
The word evolution is usually used to refer to the accumulated changes in the genetic characteristics of an entire population over time. These changes could result from the response to environmental pressures as explained in the article on Darwinism (see the entry on Charles Darwin for background), or from natural selection.
The latter is a mechanism that increases the frequency of genes in a species that confer a survival advantage over others, resulting in an ongoing change in the appearance of a population. The specific mechanisms behind these changes in evolutionary process include mutation and reshuffling of genes in sexual reproduction, as well as gene flow between populations.
Natural selection is the process that makes beneficial mutations more common. All organisms undergo changes and reshuffles of their genes. This is because, as noted above those who have the beneficial trait tend to have a higher fertility rate than those without it. This differential in the number of offspring that are produced over a long period of time can result in a gradual shift in the average number advantageous traits within the group.
An excellent example is the increase in beak size on various species of finches in the Galapagos Islands, which have developed beaks with different shapes to enable them to more easily access food in their new home. These changes in the shape and form of organisms could also aid in the creation of new species.
The majority of changes are caused by one mutation, but sometimes several occur simultaneously. Most of these changes can be harmful or neutral, but a small number could have a positive impact on survival and reproduction with increasing frequency as time passes. This is the way of natural selection and it is able to, over time, produce the accumulating changes that ultimately lead to an entirely new species.
Many people confuse the concept of evolution with the idea that inherited characteristics can be altered by conscious choice or use and abuse, a concept called soft inheritance. This is a misunderstanding of the biological processes that lead to the process of evolution. A more precise description is that evolution is a two-step process that involves the distinct and often antagonistic forces of mutation and natural selection.
Origins of Humans
Humans of today (Homo Sapiens) evolved from primates, a species of mammal species which includes gorillas and chimpanzees. The earliest human fossils prove that our ancestors were bipeds. They were walking on two legs. Genetic and biological similarities suggest that we are closely related to chimpanzees. In reality our closest relatives are chimpanzees of the Pan genus. This includes pygmy as well as bonobos. The last common ancestor of modern humans and chimpanzees was between 8 and 6 million years ago.
In the course of time humans have developed a range of traits, including bipedalism and the use of fire. They also developed advanced tools. However, it is only in the last 100,000 years or so that most of the important traits that distinguish us from other species have been developed. They include language, a large brain, the ability to create and utilize sophisticated tools, and a the diversity of our culture.
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 favored over others. Those with the better adaptations are more likely to pass on their genes to the next generation. This is the process that evolves all species and is the foundation 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 traits over time. This is because those traits allow them to live and reproduce in their natural environment.
All organisms possess a DNA molecule that contains the information needed to control their growth. 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 phenotype which is the person's distinctive appearance and behavior. Variations in a population can be caused by mutations and reshufflings in 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 a few differences in their appearance, all support the idea of the origins of modern humans in Africa. Genetic and fossil evidence also suggest that early humans came from Africa into Asia and then Europe.