The Berkeley Evolution Site
Teachers and students who browse the Berkeley site will find a wealth of resources to aid in understanding and teaching evolution. The materials are arranged in different learning paths for example "What does T. rex look like?"
Charles Darwin's theory of natural selection states that over time, animals that are more able to adapt to changing environments thrive, and those that don't become extinct. This process of evolution is what science is all about.
What is Evolution?
The word evolution can have many nonscientific meanings. For example, 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 a central tenet of modern biology. It is an established theory that has stood up to the test of time and a multitude of scientific tests. Unlike many other scientific theories, such as the Copernican theory or the germ theory of disease, the evolution theory does not address questions of spiritual belief or the existence of God.
Early evolutionists, such as Jean-Baptiste Lamarck and Erasmus Darwin (Charles's grandfather) believed that certain physical traits were predetermined to change, in a step-wise manner, as time passes. This was referred to as the "Ladder of Nature", or scala Naturae. Charles Lyell used the term to describe this concept 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 have a common ancestry which can be traced using fossils and other evidence. This is the current view on evolution, which is supported in many scientific fields which include molecular biology.
Scientists do not know the evolution of organisms however they are certain that natural selection and genetic drift are the reason for the development of life. People with traits that are advantageous are more likely to live and reproduce, and these individuals pass their genes on to the next generation. As time passes this leads to an accumulation of changes to the gene pool which gradually lead to new species and types.
Certain scientists use the term evolution in reference to large-scale change, such as the formation of one species from an ancestral one. Other scientists, such as population geneticists, define it more broadly by referring the net change in the frequency of alleles across generations. Both definitions are accurate and acceptable, but some scientists argue that allele-frequency definitions miss important aspects of the evolutionary process.
Origins of Life
One of the most crucial steps in evolution is the emergence of life. This happens when living systems begin to evolve at a micro-level - within individual cells, for example.
The origins of life are an important topic in many fields that include biology and chemical. The question of how living things got their start is a major topic in science because it is a major challenge to the theory of evolution. 무료 에볼루션 is often described as "the mystery of life" or "abiogenesis."
The notion that life could emerge from non-living things was called "spontaneous generation" or "spontaneous evolutionary". It was a common belief prior to Louis Pasteur's tests proved that the creation of living organisms was not achievable through an organic process.
Many scientists believe it is possible to move from nonliving substances to living ones. The conditions necessary to make life are not easy to replicate in a laboratory. This is why researchers investigating the origins of life are also keen to understand the physical properties of the early Earth and other planets.
Furthermore, the growth of life is dependent on an intricate sequence of chemical reactions that cannot be predicted based on basic physical laws alone. These include the reading of long information-rich molecules (DNA or RNA) into proteins that carry out a function as well as the replication of these intricate molecules to create new DNA or RNA sequences. These chemical reactions are often compared to the chicken-and-egg issue of how life came into existence with the emergence of DNA/RNA and protein-based cell machinery is essential to the birth of life, however, without the appearance of life, the chemical process that allows it does not appear to work.
무료 에볼루션 in the field of abiogenesis requires collaboration among scientists from a variety of fields. This includes prebiotic scientists, astrobiologists and planet scientists.
Evolutionary Changes
The term "evolution" is commonly used today to refer to the accumulated changes in genetic characteristics of populations over time. These changes could be the result of the adaptation to environmental pressures as explained in Darwinism.
This is a process that increases the frequency of those genes in a species that confer an advantage in survival over other species, resulting in gradual changes in the overall appearance of a population. The specific mechanisms behind these evolutionary changes include mutation or reshuffling genes during 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 happens because, as we've mentioned earlier those who have the advantageous trait are likely to have a higher reproductive rate than those who do not have it. Over many generations, this differential in the number of offspring born could result in an inclination towards a shift in the 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 that allow them to easily access food in their new home. These changes in shape and form could aid in the creation of new organisms.
The majority of the changes that occur are the result of one mutation, however occasionally, multiple mutations occur at the same time. Most of these changes are neither harmful nor even detrimental to the organism, but a small percentage can have a positive impact on survival and reproduction, thus increasing the frequency of these changes in the population over time. Natural selection is a mechanism that causes the accumulating change over time that eventually leads to the creation of a new species.
Many people confuse evolution with the idea of soft inheritance that is the belief that inherited traits can be changed by conscious choice or by abuse. This is a misunderstanding of the nature of evolution and of the actual biological processes that lead to it. It is more accurate to say that the process of evolution is a two-step, independent process, that is influenced by the forces of natural selection as well as mutation.
Origins of Humans
Humans today (Homo sapiens) evolved from primates - a species of mammals that includes chimpanzees and gorillas and bonobos. Our predecessors walked on two legs, as evidenced by the oldest fossils. Genetic and biological similarities show that we have a close relationship with chimpanzees. In reality we are the closest related to the chimpanzees within the Pan Genus, which includes bonobos and pygmy chimpanzees. The last common ancestor of humans and chimpanzees was 8 to 6 million years old.
In the course of time humans have developed a variety of characteristics, such as bipedalism and the use fire. They also invented advanced tools. It is only in the past 100,000 years or so that most of the essential characteristics that differentiate us from other species have emerged. They include language, a large brain, the ability to build and use complex tools, as well as the diversity of our culture.
Evolution happens when genetic changes allow individuals of a population to better adapt to their surroundings. This adaptation is driven by natural selection, a process that determines certain traits are more desirable than other traits. The ones with the best adaptations are more likely to pass on their genes to the next generation. This is how all species evolve, and it is the basis of the theory of evolution.
Scientists call it the "law of natural selection." The law states that species that share an ancestor will tend to acquire similar traits in the course of time. This is because these traits help them to reproduce and survive within their environment.
All organisms possess a DNA molecule that contains the information necessary to direct their growth. The DNA molecule consists of base pairs arranged spirally around phosphate molecules and sugar molecules. The sequence of bases within each strand determines the phenotype which is the person's distinctive appearance and behavior. Variations in mutations and reshuffling of the genetic material (known as alleles) during sexual reproduction can cause variation in a population.
Fossils of the earliest human species, Homo erectus and Homo neanderthalensis, have been found in Africa, Asia, and Europe. Although there are some differences they all support the hypothesis that modern humans first appeared in Africa. The fossil evidence and genetic evidence suggest that early humans moved out of Africa into Asia and then Europe.