The Berkeley Evolution Site
Students and teachers who explore the Berkeley site will find a wealth of resources to aid in understanding and teaching evolution. The materials are organized in different learning paths for example "What does T. rex look like?"
Charles Darwin's theory of natural selection explains that over time, animals that are better able to adapt biologically to changing environments thrive, and those that are not extinct. Science is concerned with this process of evolution.
What is Evolution?
The term "evolution" has a variety of nonscientific meanings, including "progress" or "descent with modification." Scientifically it is a term used to describe a change in the characteristics of living organisms (or species) over time. The reason for this change is biological terms on natural drift and selection.
Evolution is an important concept in the field of biology today. It is a well-supported theory that has stood the tests of time and thousands of scientific experiments. In contrast to other theories in science, such as the Copernican theory or the germ theory of disease, evolution is not a discussion of religion or God's existence.
Early evolutionists, including Jean-Baptiste Lamarck and Erasmus Darwin (Charles's grandfather), believed that certain physical characteristics were predetermined to change, in a step-wise manner, as time passes. They called this the "Ladder of Nature" or scala naturae. Charles Lyell used the term to describe this idea in his Principles of Geology, first published in 1833.
sell revealed his theory of evolution in his book On the Origin of Species, written in the early 1800s. It states that all species of organisms share a common ancestry which can be traced through fossils and other evidence. This is the current view of evolution, and is supported by a variety of lines of scientific research which includes molecular genetics.
While scientists do not know exactly how organisms evolved, they are confident that the evolution of life on earth is a result of natural selection and genetic drift. People with advantages are more likely to survive and reproduce. They transmit their genes on to the next generation. As time passes the gene pool slowly changes and develops into new species.
Some scientists also use the term evolution to describe large-scale evolutionary changes like the creation of an entirely new species from an ancestral species. Certain scientists, including population geneticists, define the term "evolution" in a broad sense, referring to the net change in the frequency of alleles across generations. Both definitions are valid and acceptable, but some scientists argue that allele-frequency definitions omit important features of evolutionary process.
Origins of Life
The birth of life is a crucial step in evolution. The emergence of life happens when living systems start to evolve at a micro scale, for instance within cells.
The origins of life are an important topic in a variety of fields, including biology and chemical. The question of how living things got their start has a special place in science due to it being an important challenge to the theory of evolution. It is often referred to "the mystery" of life or "abiogenesis."
Traditionally, the notion that life can emerge from nonliving things is called spontaneous generation or "spontaneous evolution." This was a common belief before Louis Pasteur's experiments showed 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 materials to living. However, the conditions required are extremely difficult to reproduce in the laboratory. This is why scientists investigating the origins of life are also interested in determining the physical properties of early Earth and other planets.
Additionally, the evolution of life is the sequence of extremely complex chemical reactions that can't be predicted based on basic physical laws alone. These include the reading and replication of complex molecules, like DNA or RNA, to create proteins that serve a specific function. These chemical reactions can be compared to the chicken-and-egg problem: the emergence and development of DNA/RNA, the protein-based cell machinery, is essential for the beginning of life. However, without life, the chemistry that is required to enable it appears to be working.
page in the area of abiogenesis requires cooperation among scientists from various disciplines. This includes prebiotic chemists planet scientists, astrobiologists, geologists and geophysicists.
Evolutionary Changes
The term "evolution" is used to describe cumulative changes in genetic characteristics over time. These changes can result from adaptation to environmental pressures, as discussed in the entry on Darwinism (see the entry on Charles Darwin for background) or may result from natural selection.
This process increases the frequency of genes that confer the advantage of survival for a species, resulting in an overall change in the appearance of an entire group. The specific mechanisms behind these changes in evolutionary process include mutation or reshuffling genes during sexual reproduction, and also gene flow between populations.
Natural selection is the process that allows beneficial mutations to become more common. All organisms undergo changes and reshuffles of their genes. This is because, as we've mentioned earlier those with the advantageous trait are likely to have a higher fertility rate than those who do not have it. Over the course of many generations, this differential in the number of offspring born can result in a gradual shift in the number of beneficial characteristics in a particular population.
One good example is the increase in the size of the beaks on different species of finches in the Galapagos Islands, which have evolved different shaped beaks to allow them to more easily access food in their new habitat. These changes in the shape and form of organisms can also help create new species.
The majority of changes are caused by a single mutation, but sometimes several occur at once. Most of these changes can be harmful or neutral however, a small percentage may have a positive effect on the survival of the species and reproduce with increasing frequency over time. Natural selection is a process that causes the accumulating change over time that eventually leads to a new species.
Some people confuse the notion of evolution with the notion that traits inherited can be altered through conscious choice, or through use and abuse, a notion called soft inheritance. This is a misinterpretation of the nature of evolution and of the actual biological processes that trigger it. A more precise description is that evolution is a two-step process that involves the distinct, and often competing, forces of natural selection and mutation.
Origins of Humans
Modern humans (Homo sapiens) evolved from primates - a species of mammals that also includes gorillas, chimpanzees, and bonobos. Our predecessors walked on two legs, as shown by the first fossils. Genetic and biological similarities suggest that we are closely related to the chimpanzees. In fact we are the closest connected to chimpanzees belonging to the Pan genus that includes pygmy and pygmy chimpanzees and bonobos. The last common ancestor of humans and chimpanzees was 8 to 6 million years old.
Humans have developed a range of traits throughout time such as bipedalism, use of fire, and the development of advanced tools. However, it is only in the past 100,000 years or so that the majority of the important traits that distinguish us from other species have been developed. These include language, large brain, the ability to create and utilize complex tools, as well as the diversity of our culture.
The process of evolution occurs when genetic changes allow individuals in a group to better adapt to their surroundings. Natural selection is the mechanism that drives this change. Certain characteristics are more desirable than others. The better adjusted are more likely to pass on their genes to the next generation. This is the process that evolves all species and is the basis of the theory of evolution.
Scientists call this the "law of natural selection." The law states that species that share an ancestor will tend to acquire similar traits over time. This is because those traits make it easier for them to live and reproduce in their environments.
All organisms have a DNA molecule, which contains the information needed to guide their growth and development. The DNA structure is composed of base pair which are arranged in a spiral, around sugar and phosphate molecules. The sequence of bases found in each strand determines the phenotype - the distinctive appearance and behavior of a person. Different changes and reshuffling of genetic material (known as alleles) during sexual reproduction cause variations in a population.
Fossils of the earliest 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 hypothesis that modern humans first appeared in Africa. The fossil evidence and genetic evidence suggest that early humans moved from Africa into Asia and then Europe.