The Berkeley Evolution Site
The Berkeley site has resources that can help students and teachers to understand and teach about evolution. The materials are organized into a variety of learning paths, such as "What did T. rex taste like?"
Charles Darwin's theory of natural selection explains that over time creatures that are more able to adapt to changing environments do better than those that don't become extinct. Science is concerned with this process of biological evolution.
What is Evolution?
The word evolution has many nonscientific meanings, such as "progress" or "descent with modification." It is an academic term that is used to describe the process of changing traits over time in organisms or species. In biological terms, this change is caused by natural selection and genetic drift.
Evolution is a fundamental principle in modern biology. It is a theory that has been tested and confirmed through thousands of scientific tests. Evolution doesn't deal with the existence of God or religious beliefs in the same way as other theories in science, like the Copernican or germ theory of diseases.
Early evolutionists such as Erasmus Darwin (Charles’s grandfather) and Jean-Baptiste Lamarck believed that certain physical characteristics were predetermined to evolve in a stepped-like manner over time. This was known as the "Ladder of Nature" or 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 asserts that different species of organisms have a common ancestry, which can be proven through fossils and other evidence. This is the current understanding of evolution that is supported by a variety of lines of research in science that include molecular genetics.
While scientists don't know the exact mechanism by which organisms evolved but they are certain that the evolution of life on earth is the 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 evolves into new species.
Some scientists also employ the term"evolution" to refer to large-scale evolutionary changes such as the creation of a new species from an ancestral species. Some scientists, like population geneticists define evolution in a broader sense by using the term "net change" to refer to the variation in the frequency of alleles over generations. Both definitions are acceptable and precise however, some scientists claim that the allele-frequency definition is missing crucial aspects of the evolutionary process.
Origins of Life
One of the most crucial steps in evolution is the appearance of life. The emergence of life occurs when living systems begin to evolve at a micro level, like within individual cells.
The origins of life is an issue in a variety of disciplines that include biology, chemistry and geology. The nature of life is a topic of great interest in science, as it challenges the theory of evolution. It is often called "the mystery of life" or "abiogenesis."
The notion that life could be born from non-living matter was known as "spontaneous generation" or "spontaneous evolutionary". This was a popular belief prior to Louis Pasteur's tests showed that the emergence of living organisms was not possible through the natural process.
Many scientists believe it is possible to move from nonliving substances to living ones. However, the conditions that are required are extremely difficult to reproduce in the laboratory. Researchers investigating the nature of life are also keen to understand the physical properties of early Earth and other planets.
The development of life is dependent on a variety of complex chemical reactions, which cannot be predicted by simple physical laws. These include the reading of long information-rich molecules (DNA or RNA) into proteins that perform a function, and the replication of these complex molecules to create new DNA or RNA sequences. These chemical reactions are often compared with the chicken-and-egg dilemma of how life first appeared with the appearance of DNA/RNA and protein-based cell machinery is essential for the onset of life, however, without the development of life the chemical process that allows it does not appear to work.
Research in the area of abiogenesis requires collaboration among scientists from many different fields. This includes prebiotic scientists, astrobiologists, and planetary scientists.
Evolutionary Changes
The term "evolution" is typically used today to describe the cumulative changes in the genetic characteristics of populations over time. These changes could be the result of adaptation to environmental pressures as explained in Darwinism.
This is a process that increases the frequency of genes in a species that confer an advantage in survival over others which results in an ongoing change in the overall appearance of a particular population. These evolutionary changes are caused by mutations, reshuffling of genes during sexual reproduction and gene flow.
While reshuffling and mutation of genes are common in all organisms and the process by which beneficial mutations are more frequent is called natural selection. As previously mentioned, those who possess the desirable trait have a higher reproductive rate than those who do not. This variation in the number of offspring produced over many generations can result in a gradual shift in the average number of beneficial traits within a group.
This can be seen in the evolution of different beak designs on finches that are found in the Galapagos Islands. They have developed these beaks so that they can access food more quickly in their new home. These changes in the form and shape of organisms could also help create new species.
The majority of changes are caused by one mutation, although sometimes multiple occur simultaneously. The majority of these changes could be harmful or neutral, but a small number may have a positive effect on survival 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 leads to a new species.
Many people confuse the concept of evolution with the idea that the traits inherited from parents can be altered by conscious choice, or through use and abuse, a notion called soft inheritance. 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 involves the forces of natural selection and mutation.
Origins of Humans
Modern humans (Homo sapiens) evolved from primates, a group of mammals that also includes gorillas, chimpanzees, and bonobos. The earliest human fossils indicate that our ancestors were bipeds. They were walking on two legs. Genetic and biological similarities show that we have an intimate relationship with the chimpanzees. In actual fact we are the most closely related to the chimpanzees within the Pan genus, which includes pygmy chimpanzees and bonobos. The last common human ancestor and chimpanzees lived between 8 and 6 million years ago.
Humans have evolved a wide range of characteristics over time including bipedalism, the use of fire, and the development of advanced tools. It is only within the last 100,000 years that we have developed the majority of our essential characteristics. These include language, large brain, the capacity to create and utilize complex tools, as well as cultural diversity.
The process of evolution is when genetic changes allow members of an organization to better adapt to the environment. Natural selection is the process that drives this change. Certain characteristics are more desirable than others. Those with the better adaptations are more likely to pass on their genes to the next generation. This is the way all species evolve and is the foundation for the theory of evolution.
Scientists refer to it as the "law of natural selection." 무료 에볼루션 states species that have an ancestor in common will tend to develop similar characteristics in the course of time. This is because these traits allow them to live and reproduce in their environment.
All organisms possess an molecule called DNA that holds the information necessary to direct their growth. The DNA molecule is made up of base pairs that are spirally arranged around sugar molecules and phosphate molecules. The sequence of bases within each strand determines the phenotype, or the individual's characteristic appearance and behavior. The variations in a population are caused by mutations and reshufflings of genetic material (known collectively as alleles).
Fossils from the early human species Homo erectus and Homo neanderthalensis have been discovered in Africa, Asia and Europe. Although there are some differences they all support the hypothesis that modern humans first appeared in Africa. Genetic and fossil evidence also suggest that early humans migrated from Africa into Asia and then Europe.