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 organized into optional learning paths, such as "What did T. rex taste like?"
Charles Darwin's theory of natural selection explains how creatures who are better able to adapt to changes in their environments survive longer and those that don't become extinct. Science is all about this process of biological evolution.
What is Evolution?
The term "evolution" could have a variety of meanings that are not scientific. For instance, it can mean "progress" and "descent with modifications." It is scientifically based and refers to the process of change of characteristics in a species or species. In biological terms the change is due to natural selection and genetic drift.
Evolution is a central tenet of modern biology. It is a theory that has been tested and proven by a myriad of scientific tests. Evolution doesn't deal with the existence of God or religious beliefs like other theories of science, such as the Copernican or germ theory of disease.
Early evolutionists, like 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. They called this 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 all species of organisms have common ancestors that can be traced using fossils and other evidence. This is the modern view of evolution, which is supported by numerous lines of scientific research that include molecular genetics.
While scientists do not know exactly how organisms evolved, they are confident that the evolution of life on earth is the result of natural selection and genetic drift. Individuals with advantageous 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.
Some scientists use the term evolution in reference to large-scale changes, like the development of one species from an ancestral one. Other scientists, such as population geneticists, define it more broadly, referring to an overall variation in the frequency of alleles over generations. Both definitions are acceptable and accurate, although some scientists argue that the allele-frequency definition omits essential aspects of the evolution process.
Origins of Life
One of the most crucial steps in evolution is the development of life. The beginning of life takes place when living systems begin to develop at a microscopic scale, for instance within cells.
The origins of life are an issue in a variety of disciplines such as biology, chemistry, and geology. The question of how living things started is a major topic in science since it poses an enormous challenge to the theory of evolution. It is often referred to as "the mystery of life" or "abiogenesis."
The notion that life could arise from non-living objects was referred to as "spontaneous generation" or "spontaneous evolutionary". It was a common belief prior to Louis Pasteur's experiments proved that the development of living organisms was not achievable through an organic process.
Many scientists believe it is possible to go from nonliving substances to living ones. The conditions required for the creation of life are difficult to reproduce in a lab. Researchers investigating the nature of life are also interested in determining the physical properties of the early Earth and other planets.
The life-cycle of a living organism is also dependent on a series of complex chemical reactions, that are not predicted by simple physical laws. These include the reading and re-reading of complex molecules, like DNA or RNA, to create proteins that perform a specific function. These chemical reactions can be compared with a chicken-and egg problem that is the emergence and growth of DNA/RNA, a protein-based cell machinery, is essential to begin the process of becoming a living organism. Although, without life, the chemistry needed to enable it appears to be working.
Research in the field of abiogenesis requires collaboration among scientists from various disciplines. This includes prebiotic chemists astrobiologists, planetary scientists, geologists and geophysicists.
Evolutionary Changes
Today, the word evolution is used to describe the cumulative changes in genetic characteristics over time. These changes may result from adaptation to environmental pressures as discussed in the entry on Darwinism (see the entry on Charles Darwin for background), or from natural selection.
This is a process that increases the frequency of genes which confer an advantage in survival over others and causes an ongoing change in the overall appearance of a particular population. The specific mechanisms behind these changes in evolutionary process include mutation and reshuffling of genes in sexual reproduction, and also gene flow between populations.
Natural selection is the process that allows beneficial mutations to become more common. All organisms undergo mutations and reshuffles of genes. As mentioned above, those who have the advantageous trait have a higher reproductive rate than those that do not. Over the course of many generations, this difference in the number of offspring born could result in gradual changes in the average number of advantageous traits in a population.
A good example of this is the increase in the size of the beaks on different species of finches found on the Galapagos Islands, which have developed different beak shapes that allow them to easily access food in their new home. These changes in the shape and form of living organisms may also be a catalyst for the creation of new species.
The majority of changes are caused by a single mutation, but sometimes several occur at the same time. The majority of these changes could be neutral or even harmful however, a small percentage could have a positive impact on survival and reproduce with increasing frequency as time passes. Natural selection is a process that causes the accumulating change over time that eventually leads to the creation of a new species.
Some people confuse evolution with the idea of soft inheritance, which is the idea that traits inherited from parents can be altered by conscious choice or abuse. This is a misunderstood understanding 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 antagonistic forces of mutation and natural selection.
Origins of Humans
Humans today (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 walkers on two legs. Genetic and biological similarities show that we share the same ancestry with chimpanzees. In actual fact our closest relatives are the chimpanzees of the Pan genus. This includes pygmy as well as bonobos. The last common ancestor of modern humans 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 advanced tools. It's only within the last 100,000 years that we've developed the majority of our key traits. They include language, a large brain, the ability to build and use complex tools, and the ability to adapt to cultural differences.
The process of evolution occurs when genetic changes enable members of a group to better adapt to their environment. This adaptation is driven by natural selection, which is a process by which certain traits 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 the foundation for the theory of evolution.
Scientists refer to this as the "law of natural selection." The law states that species that have a common ancestor are more likely to develop similar traits over time. This is because the characteristics make it easier for them to live and reproduce in their natural environment.
Every organism has a DNA molecule, which is the source of information that helps guide their growth and development. The structure of DNA is made of base pairs that are arranged in a spiral around phosphate and sugar molecules. The sequence of bases within each strand determines the phenotype - the appearance and behavior of an individual. pop over here in a population can be caused by mutations and reshufflings in genetic material (known collectively as alleles).
에볼루션 슬롯 from the first human species, Homo erectus and Homo neanderthalensis have been discovered in Africa, Asia and Europe. These fossils, despite some differences in their appearance, all support the theory of modern humans' origins in Africa. The fossil and genetic evidence suggests that early humans left Africa and moved to Asia and Europe.