The Berkeley Evolution Site
Teachers and students who visit the Berkeley site will find resources to aid in understanding and teaching evolution. The resources are organized into a variety of learning paths like "What did T. rex taste like?"
Charles Darwin's theory of natural selection explains how over time, animals that are better able to adapt biologically to changing environments do better than those that don't become extinct. Science is concerned with the process of biological evolution.
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." Scientifically, it refers to a process of changing the characteristics of living organisms (or species) over time. This change is based in biological terms on natural drift and selection.
Evolution is the central tenet of modern biology. It is a well-supported theory that has withstood the test of time and thousands of scientific experiments. Contrary to other theories of science 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, such as Jean-Baptiste Lamarck and Erasmus Darwin (Charles's grandfather), believed that certain physical characteristics were predetermined to change, in a gradual manner, over time. They called this the "Ladder of Nature" or scala naturae. Charles Lyell first used this term in 1833 in his Principles of Geology.
Darwin presented his theory of evolution in his book On the Origin of Species published in the early 1800s. It asserts that all species of organisms share an ancestry that can be traced using fossils and other evidence. This is the current understanding of evolution, which is supported by numerous research lines in science which includes molecular genetics.
While scientists do not know exactly how organisms developed, 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 than others to survive and reproduce. They then pass their genes to the next generation. Over time this leads to gradual changes to the gene pool that gradually create new species and types.
Certain scientists use the term"evolution" in reference to large-scale changes, such the development of an animal from an ancestral one. Others, like population geneticists, define the term "evolution" more broadly by referring to a net change in the frequency of alleles across generations. Both definitions are correct and acceptable, however some scientists argue that allele-frequency definitions miss important aspects of the evolution.
Origins of Life
One of the most crucial steps in evolution is the development of life. The emergence of life occurs when living systems start to evolve at a micro level, like within individual cells.
The origins of life is one of the major topics in various disciplines that include biology, chemistry and geology. The origin of life is an area of interest in science because it challenges the theory of evolution. It is sometimes referred to "the mystery" of life or "abiogenesis."
Traditionally, the notion that life can emerge 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 creation of life to occur by the natural process.
Many scientists still believe it is possible to transition from nonliving substances to life. The conditions required to create life are difficult to replicate in a laboratory. This is why scientists investigating the nature 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 a sequence of very complex chemical reactions that can't be predicted from basic physical laws alone. These include the reading of long information-rich molecules (DNA or RNA) into proteins that perform some function and the replication of these intricate molecules to generate new DNA or RNA sequences. These chemical reactions are often compared with the chicken-and-egg issue of how life first appeared with the development of DNA/RNA as well as protein-based cell machinery is essential for the onset of life, but without the emergence of life, the chemical reaction that is the basis for it does not appear to work.
Abiogenesis research requires collaboration between scientists from different fields. This includes prebiotic scientists, astrobiologists and planet scientists.
Evolutionary Changes
The word evolution is usually used to refer to the accumulated changes in the genetic traits of populations 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 natural selection.
This latter mechanism increases the number of genes that offer the advantage of survival for an animal, resulting in an overall change in the appearance of a group. The specific mechanisms that cause these evolutionary changes are mutation or reshuffling genes during sexual reproduction, and gene flow between populations.
While reshuffling and mutation of genes occur in all living things The process through which beneficial mutations are more prevalent is referred to as natural selection. This happens because, as noted above those who have the advantageous trait are likely to have a higher reproduction rate than those who do not have it. This variation in the number of offspring that are produced over a long period of time can result in a gradual change in the number of advantageous traits in a group.
This is evident in the evolution of different beak shapes for finches from the Galapagos Islands. They have created these beaks to ensure they can get food more easily in their new habitat. These changes in form and shape can also help create new organisms.
The majority of changes are caused by one mutation, but sometimes several occur at once. The majority of these changes are neutral or even harmful to the organism however, a small proportion of them can have an advantageous impact on the survival of the organism and its reproduction, thereby increasing the frequency of these changes in the population over time. Natural selection is a mechanism that could result in the accumulation of change over time that eventually leads to a new species.
Many people think that evolution is a form of soft inheritance which is the notion that inherited traits can be changed by conscious choice or by abuse. This is a misunderstanding of the biological processes that lead to evolution. 에볼루션 게이밍 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 and mutation.
Origins of Humans
Humans of today (Homo Sapiens) evolved from primates, a group of mammal species which includes chimpanzees as well as gorillas. Our ancestors walked on two legs, as evidenced by the earliest fossils. Biological and genetic similarities indicate that we share the same ancestry with Chimpanzees. In fact we are the closest with chimpanzees in the Pan Genus that includes pygmy and bonobos and pygmy chimpanzees. The last common human ancestor and chimpanzees lived between 8 and 6 million years ago.
Humans have evolved a wide range of traits throughout time such as bipedalism, use of fire and advanced tools. It is only within the last 100,000 years that we've developed the majority of our essential traits. 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 enable members of an organization to better adapt to their environment. Natural selection is the mechanism that drives this change. Certain characteristics are more desirable than others. The ones who are better adapted are more likely to pass their genes on to the next generation. This is the way that all species evolve and forms the basis of the theory of evolution.
Scientists refer to this as the "law of natural selection." The law states species that have an ancestor in common will tend to develop similar traits over time. This is because these traits allow them to reproduce and survive within their environment.
All organisms have DNA molecules, which contains the information needed to direct their growth and development. 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, or the individual's characteristic appearance and behavior. Variations in a population can be caused by mutations and reshufflings in genetic material (known collectively as alleles).
Fossils from the first human species, Homo erectus, as well as Homo neanderthalensis have been found in Africa, Asia and Europe. These fossils, despite differences in their appearance, all support the theory of the origins of modern humans in Africa. The genetic and fossil evidence suggests that the first humans left Africa and moved to Asia and Europe.