The Berkeley Evolution Site
Teachers and students who browse the Berkeley site will find resources to help them understand and teach 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 more able to adapt to changing environments do better than those that are not extinct. This process of evolution is what science is all about.
What is Evolution?
The word evolution has many nonscientific meanings, including "progress" or "descent with modification." Scientifically it is a term used to describe a change in the characteristics of organisms (or species) over time. In terms of biology the change is caused by natural selection and genetic drift.
Evolution is a central tenet of modern biology. It is a concept that has been proven by thousands of scientific tests. Contrary to other theories of science, such as the Copernican theory or the germ theory of disease, evolution does not address questions of religious belief or the existence of God.
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 way, over time. This was called 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 asserts that different species of organisms have an ancestry that can be determined through fossils and other evidence. This is the modern view on evolution, which is supported by a variety of scientific fields that include molecular biology.
While scientists do not know the exact mechanism by which 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 survive and reproduce, and these individuals pass their genes on to the next generation. Over time the gene pool slowly changes and evolves into new species.
Certain scientists also use the term"evolution" to refer to large-scale evolutionary changes such as the creation of a new species from an ancestral species. Other scientists, such as population geneticists, define it more broadly by referring to an overall change in allele frequencies over generations. Both definitions are correct and palatable, but some scientists believe that allele-frequency definitions omit important features of evolution.
Origins of Life
The most important step in evolution is the appearance of life. 에볼루션코리아 of life takes place when living systems start to develop at a micro scale, for instance within cells.
The origin of life is one of the major topics in various disciplines such as biology, chemistry, and geology. The origin of life is an area that is of immense interest to scientists, as it challenges the theory of evolution. It is sometimes referred to "the mystery" of life or "abiogenesis."
The idea that life could emerge from non-living things was called "spontaneous generation" or "spontaneous evolutionary". This was a popular belief prior to Louis Pasteur's tests showed that the development of living organisms was not possible through the natural process.
Many scientists still believe it is possible to transition from nonliving materials to living. The conditions necessary to create life are difficult to replicate in a laboratory. Researchers interested in the evolution and origins of life are also keen to learn about the physical characteristics of the early Earth as well as other planets.
Additionally, the evolution of life is dependent on the sequence of extremely complex chemical reactions that can't be predicted based on basic physical laws on their own. This includes the conversion of long information-rich molecules (DNA or RNA) into proteins that carry out some function and the replication of these intricate molecules to create new DNA or sequences of RNA. These chemical reactions are often compared with the chicken-and-egg issue of how life first appeared in the first place. The emergence of DNA/RNA and proteins-based cell machinery is vital for the beginning of life, but without the emergence of life the chemical process that allows it is not working.
Research in the area of abiogenesis requires collaboration between scientists from a variety of fields. This includes prebiotic scientists, astrobiologists and planet scientists.
Evolutionary Changes
The term "evolution" today is used to describe cumulative changes in genetic characteristics over time. These changes can be the result of adaptation to environmental pressures as described in Darwinism.
This process increases the frequency of genes that offer the advantage of survival for the species, leading to an overall change in the appearance of the group. These evolutionary changes are caused by mutations, reshuffling of genes during sexual reproduction and gene flow.
Natural selection is the process that allows beneficial mutations to become more common. All organisms undergo mutations and reshuffles of their genes. This occurs because, as noted above, those individuals with the beneficial trait tend to have a higher reproductive rate than those without it. This variation in the number of offspring born over a long period of time can result in a gradual shift in the average number advantageous traits within a group.
One good example is the growing beak size on different species of finches on the Galapagos Islands, which have developed beaks with different shapes to allow them to more easily access food in their new home. These changes in the shape and appearance of organisms can also help create new species.
The majority of changes are caused by one mutation, but sometimes several occur simultaneously. 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 and increase their frequency as time passes. Natural selection is a process that could result in the accumulation of change over time that eventually leads to the creation of a new species.
Many people confuse the concept of evolution with the notion that the traits inherited from parents can be altered by conscious choice or use and abuse, a concept known as soft inheritance. This is a misunderstanding of the nature of evolution, and of the actual biological processes that trigger it. A more accurate description is that evolution is a two-step process involving the independent and often conflicting forces of natural selection and mutation.
Origins of Humans
Humans of today (Homo Sapiens) evolved from primates, a group of mammal species which includes gorillas and chimpanzees. Our ancestors walked on two legs, as shown by the oldest fossils. Genetic and biological similarities suggest that we are closely related to chimpanzees. In reality, we are most closely with chimpanzees in the Pan Genus that includes pygmy and bonobos and pygmy chimpanzees. The last common ancestor of modern humans and chimpanzees was born between 8 and 6 million years ago.
Humans have developed a range of traits throughout time, including bipedalism, the use of fire and advanced tools. It is only in the last 100,000 years or so that most of the essential characteristics that differentiate us from other species have emerged. These include language, a large brain, the ability to build and use complex tools, and the ability to adapt to cultural differences.
Evolution occurs when genetic changes allow individuals of a population to better adapt to their surroundings. This adaptation is triggered by natural selection, which is a process by which certain traits are favored over other traits. The more adaptable are more likely to pass on their genes to the next generation. This is the way that all species evolve, and it is the basis of the theory of evolution.
Scientists refer to it as the "law of natural selection." The law says that species that have a common ancestor, tend to develop similar characteristics over time. It is because these traits allow them to live and reproduce in their environment.
Every organism has an molecule called DNA that holds the information necessary to direct their growth. The DNA molecule consists of base pairs that are spirally arranged around sugar molecules and phosphate molecules. The sequence of bases found in each strand determines the phenotype - the appearance and behavior of a person. A variety of mutations and reshuffling 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 discovered in Africa, Asia, and Europe. These fossils, despite variations in their appearance, all support the idea that modern humans' ancestors originated in Africa. The fossil and genetic evidence suggests that early humans left Africa and migrated to Asia and Europe.