The Berkeley Evolution Site
The Berkeley site contains resources that can help students and educators to understand and teach about evolution. The resources are organized into optional learning paths such as "What did T. rex taste like?"
Charles Darwin's theory of natural selection explains how animals who are better able to adapt biologically to a changing environments survive longer and those who do not end up becoming extinct. Science is concerned with this process of biological evolutionary change.
What is Evolution?
The term "evolution" can have a variety of meanings that are not scientific. For example, it can mean "progress" and "descent with modifications." It is a scientific term that refers to the process of change of characteristics over time in organisms or species. This change is based in biological terms on natural selection and drift.
Evolution is an important tenet in modern biology. It is an accepted theory that has withstood the test of time and a multitude of scientific tests. Contrary to other theories of 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 gradual manner, over time. This was referred to as 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.
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 share a common ancestry which can be traced using fossils and other evidence. This is the current understanding of evolution, which is supported by a variety of lines of research in science which includes molecular genetics.
While scientists don't 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 desirable traits are more likely to live and reproduce, and these individuals pass their genes on to the next generation. Over time, the gene pool gradually changes and develops into new species.
Certain scientists use the term"evolution" in reference to large-scale changes, like the formation of one species from an ancestral one. Certain scientists, including population geneticists, define the term "evolution" in a broad sense, talking about the net variation in the frequency of alleles over generations. Both definitions are acceptable and accurate however, some scientists claim that the allele-frequency definition is missing important features of the evolutionary process.
Origins of Life
The birth of life is a key stage in evolution. The beginning of life takes place when living systems begin to evolve at a micro level, like within cells.
The origins of life are an important issue in many disciplines, including biology and chemical. The nature of life is a topic of interest in science, as it is a challenge to the theory of evolution. It is often referred to "the mystery" of life or "abiogenesis."
Traditionally, the idea that life can arise from nonliving things is known as 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 a purely natural process.
Many scientists believe that it is possible to transition from nonliving substances to living. However, the conditions required are extremely difficult to replicate in a laboratory. This is why scientists investigating the beginnings of life are also interested in determining the physical properties of the early Earth and other planets.
Furthermore, the growth of life is dependent on a sequence of very complex chemical reactions that can't be predicted from basic physical laws on their own. These include the reading of long information-rich molecules (DNA or RNA) into proteins that carry out functions as well as the replication of these complex molecules to create new DNA or sequences of RNA. These chemical reactions are often compared with the chicken-and-egg dilemma of how life began with the development of DNA/RNA as well as protein-based cell machinery is essential for the beginning of life, however, without the appearance of life the chemical process that allows it isn't working.
Abiogenesis research requires collaboration among scientists from different fields. This includes prebiotic chemists, planet scientists, astrobiologists, geologists and geophysicists.
Evolutionary Changes
The term "evolution" today is used to describe cumulative changes in genetic characteristics over time. These changes could 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 latter mechanism increases the number of genes that confer a survival advantage in the species, leading to an overall change in the appearance of an entire group. These evolutionary changes are triggered by mutations, reshuffling of genes in the process of sexual reproduction, and also by the flow of genes.
While reshuffling and mutation of genes happen in all living things The process through which beneficial mutations become more common is known as natural selection. This is because, as mentioned above those who have the beneficial trait tend to have a higher reproduction rate than those who do not have it. Over many generations, this differential in the number of offspring produced can result in an inclination towards a shift in the average amount of desirable characteristics in a particular population.
An excellent example is the growth of the size of the beaks on different species of finches on the Galapagos Islands, which have developed different beak shapes that allow them to easily access food in their new environment. These changes in the form and shape of living organisms may also aid in the creation of new species.
The majority of the changes that occur are caused by one mutation, but occasionally, multiple mutations occur simultaneously. The majority of these changes could be harmful or neutral however, a few can have a beneficial impact on survival and reproduction and increase their frequency as time passes. Natural selection is a mechanism that can produce the accumulating change over time that eventually leads to a new species.
Some people confuse the idea of evolution with the notion that the traits inherited from parents can be changed through conscious choice or use and abuse, a notion called soft inheritance. This is a misinterpretation of the biological processes that lead to evolution. It is more accurate to say that the process of evolution is a two-step, separate process, that is influenced by the forces of natural selection and mutation.
Origins of Humans
Modern humans (Homo Sapiens) evolved from primates, a species 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. Genetic and biological similarities suggest that we have the same ancestry with Chimpanzees. In actual fact, our closest relatives are the chimpanzees from the Pan genus. Suggested Studying includes pygmy as well as bonobos. The last common human ancestor and chimpanzees was between 8 and 6 million years ago.
As time has passed, humans have developed a variety of characteristics, such as bipedalism and the use fire. They also invented advanced tools. It's only in the last 100,000 years that we have developed the majority of our essential traits. They include language, a large brain, the ability to construct and use sophisticated tools, and a the ability to adapt to cultural differences.
Evolution occurs when genetic changes allow members of the group to better adapt to the environment. Natural selection is the mechanism that drives this change. Certain traits are preferred over others. Those with the better adaptations are more likely to pass their genes to the next generation. This is the way that all species evolve and forms 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 traits as time passes. It is because these traits allow them to reproduce and survive within their environment.
Every organism has a DNA molecule that contains the information needed to guide their growth. The DNA molecule consists of base pairs that are arranged in a spiral around sugar molecules and phosphate molecules. The sequence of bases within each strand determines phenotype or the individual's unique appearance and behavior. Different mutations and reshuffling of the genetic material (known as alleles) during reproduction causes variation in a population.
Fossils of the first human species, Homo erectus and Homo neanderthalensis, have been found in Africa, Asia, and Europe. While there are some differences between them, these fossils all support the notion that modern humans first came into existence in Africa. The fossil evidence and genetic evidence suggest that early humans came from Africa into Asia and then Europe.