The Berkeley Evolution Site
Students and teachers who explore the Berkeley site will find a wealth of resources to assist them in understanding and teaching evolution. The materials are arranged into different learning paths like "What did T. rex taste like?"
news of natural selection explains that over time, animals that are better able to adapt biologically to changing environments do better than those that don't become extinct. This process of biological evolution is the basis of science.
What is Evolution?
The term "evolution" can have a variety of meanings that are not scientific. For example it could mean "progress" and "descent with modifications." It is an academic term that is used to describe the process of changing characteristics over time in organisms or species. This change is based in biological terms on natural selection and drift.
Evolution is a key concept in modern biology. It is an accepted theory that has stood up to the test of time and thousands of scientific experiments. It does not address spiritual beliefs or God's presence like other scientific theories such as the Copernican or germ theory of diseases.
Early evolutionists such as Erasmus Darwin (Charles’s grandfather) and Jean-Baptiste Lamarck believed that certain physical traits were predetermined to change in a stepped-like manner over time. They referred to this as the "Ladder of Nature" or the 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 view of evolution, which is supported in a wide range of disciplines that include molecular biology.
Although scientists aren't able to determine exactly how organisms evolved, they are confident that the evolution of life on earth is a result of natural selection and genetic drift. Individuals with advantageous characteristics are more likely to survive and reproduce. These individuals pass on their genes on to the next generation. Over time the gene pool gradually changes and develops into new species.
Some scientists use the term evolution in reference to large-scale changes, such the formation of a species from an ancestral one. Other scientists, like population geneticists, define the term "evolution" more broadly by referring to an overall change in the frequency of alleles across generations. Both definitions are accurate and acceptable, however certain scientists argue that allele frequency definitions omit important features of evolution.
Origins of Life
A key step in evolution is the appearance of life. This occurs when living systems begin to evolve at the micro level - within cells, for instance.
The origin of life is one of the major topics in various disciplines that include geology, chemistry, biology and chemistry. The nature of life is an area that is of immense interest to scientists, as it challenges the theory of evolution. It is often described as "the mystery of life," or "abiogenesis."
Traditionally, the notion that life can arise from nonliving things is known as spontaneous generation, or "spontaneous evolution." This was a popular belief prior to Louis Pasteur's experiments showed that it was impossible for the emergence of life to occur by an entirely natural process.
Many scientists still believe that it is possible to transition from nonliving materials to living. The conditions needed to make life are not easy to replicate in a laboratory. This is why scientists studying the beginnings of life are also keen to understand the physical properties of early Earth and other planets.
The life-cycle of a living organism is dependent on a number of complex chemical reactions which cannot be predicted by basic physical laws. These include the transformation of long information-rich molecules (DNA or RNA) into proteins that carry out functions and the replication of these complex molecules to produce new DNA or sequences of RNA. These chemical reactions can be compared to the chicken-and-egg problem that is the emergence and growth of DNA/RNA, a protein-based cell machinery, is essential for the beginning of life. Although, without life, the chemistry required to create it appears to be working.
Research in the area of abiogenesis requires collaboration between scientists from a variety of fields. This includes prebiotic chemists the astrobiologists, the planet scientists geophysicists and geologists.
Evolutionary Changes
The word evolution is usually used to describe the accumulated changes in the genetic characteristics of a population over time. These changes can result from adaptation to environmental pressures, as explained in the article on Darwinism (see the entry on Charles Darwin for background), or from natural selection.
This process increases the number of genes that provide the advantage of survival for the species, leading to an overall change in the appearance of a group. These changes in evolutionary patterns are caused by mutations, reshuffling genes during sexual reproduction, and gene flow.
While reshuffling and mutations of genes happen in all organisms and the process by which beneficial mutations become more common is called natural selection. As previously mentioned, those with the beneficial characteristic have a higher reproduction rate than those that do not. This differential in the number of offspring produced over a number of generations could result in a gradual shift in the average number advantageous characteristics in the group.
One good example is the growing the size of the beaks on different species of finches in the Galapagos Islands, which have developed different beak shapes that allow them to easily access food in their new environment. These changes in form and shape can also aid in the creation of new species.
Most of the changes that occur are caused by a single mutation, but occasionally several will happen at once. Most of these changes can be neutral or even harmful, but a small number may have a positive effect on the survival of the species and reproduce and increase their frequency as time passes. Natural selection is a process that could result in the accumulation of changes over time that lead to a new species.
Some people mistakenly associate evolution with the concept of soft inheritance, which is the idea that traits inherited from parents can be changed through deliberate choice or misuse. This is a misunderstanding of the nature of evolution and of the actual biological processes that cause it. A more accurate description of evolution is that it is a two-step process involving the independent, and often competing, forces of mutation and natural selection.
Origins of Humans
Humans today (Homo sapiens) evolved from primates - a group of mammals that includes chimpanzees, gorillas, and bonobos. The earliest human fossils indicate that our ancestors were bipeds - walking on two legs. Biological and genetic similarities indicate that we share a close relationship with Chimpanzees. In fact we are the closest with chimpanzees in the Pan Genus, which includes pygmy chimpanzees and bonobos. The last common ancestor of modern humans and chimpanzees was between 8 and 6 million years ago.
Humans have evolved a wide range of characteristics over time including bipedalism, the use of fire and advanced tools. But it's only in the past 100,000 years or so that the majority of the important characteristics that differentiate us from other species have been developed. They include language, a large brain, the ability to create and utilize sophisticated tools, and a the ability to adapt to cultural differences.
Evolution occurs when genetic changes enable members of a group to better adapt to their environment. This adaptation is triggered by natural selection, which is a process by which certain traits are more desirable than others. People with better adaptations are more likely to pass their genes to the next generation. This is the way all species evolve and the basis for the theory of evolution.
click through the following article 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 as time passes. This is because these characteristics make it easier for them to live and reproduce in their environments.
Every living thing has a DNA molecule that provides the information necessary to direct their growth and development. The DNA molecule is composed of base pairs that are arranged in a spiral around sugar molecules and phosphate molecules. The sequence of bases in each strand determines the phenotype, the characteristic appearance and behavior of a person. Different mutations and reshufflings of the genetic material (known as alleles) during sexual reproduction can cause variation in a group.
Fossils from the earliest human species Homo erectus and Homo neanderthalensis have been found in Africa, Asia and Europe. Although there are some differences, these fossils all support the notion that modern humans first came into existence in Africa. The fossil and genetic evidence suggests that early humans left Africa and migrated to Asia and Europe.