What is Free Evolution?
Free evolution is the concept that the natural processes of organisms can lead them to evolve over time. This includes the appearance and development of new species.
Numerous examples have been offered of this, including different kinds of stickleback fish that can live in either fresh or salt water and walking stick insect varieties that prefer particular host plants. These reversible traits can't, however, explain fundamental changes in body plans.
Evolution by Natural Selection
Scientists have been fascinated by the evolution of all living creatures that inhabit our planet for many centuries. The most well-known explanation is that of Charles Darwin's natural selection, an evolutionary process that occurs when better-adapted individuals survive and reproduce more successfully than those who are less well adapted. Over time, a community of well-adapted individuals increases and eventually becomes a new species.
Natural selection is a process that is cyclical and involves the interaction of 3 factors: variation, reproduction and inheritance. Variation is caused by mutation and sexual reproduction both of which increase the genetic diversity of a species. Inheritance refers to the passing of a person's genetic traits to their offspring, which includes both recessive and dominant alleles. Reproduction is the production of viable, fertile offspring, which includes both sexual and asexual methods.
Natural selection only occurs when all of these factors are in equilibrium. If, for instance the dominant gene allele allows an organism to reproduce and survive more than the recessive allele then the dominant allele will become more prevalent in a population. But if the allele confers a disadvantage in survival or decreases fertility, it will be eliminated from the population. The process is self reinforcing meaning that the organism with an adaptive trait will live and reproduce much more than those with a maladaptive trait. The more offspring an organism can produce the better its fitness that is determined by its capacity to reproduce and survive. People with good characteristics, like longer necks in giraffes or bright white color patterns in male peacocks are more likely survive and have offspring, which means they will become the majority of the population in the future.
Natural selection is only a factor in populations and not on individuals. This is a major distinction from the Lamarckian theory of evolution, which argues that animals acquire characteristics by use or inactivity. For example, if a giraffe's neck gets longer through stretching to reach for prey its offspring will inherit a larger neck. The difference in neck size between generations will continue to increase until the giraffe is unable to breed with other giraffes.
Evolution through Genetic Drift
In genetic drift, alleles within a gene can be at different frequencies in a population due to random events. At some point, one will attain fixation (become so common that it cannot be removed through natural selection), while the other alleles drop to lower frequency. This could lead to a dominant allele in the extreme. The other alleles are virtually eliminated and heterozygosity been reduced to zero. In a small group this could lead to the complete elimination of recessive gene. Such a scenario would be known as a bottleneck effect and it is typical of evolutionary process that takes place when a lot of people migrate to form a new population.
A phenotypic 'bottleneck' can also occur when the survivors of a disaster such as an outbreak or mass hunt event are confined to an area of a limited size. The survivors will have a dominant allele and thus will share the same phenotype. This could be caused by a conflict, earthquake or even a disease. Regardless of the cause the genetically distinct group that is left might be prone to genetic drift.
에볼루션 룰렛 , Walsh, and Ariew define drift as a deviation from expected values due to differences in fitness. They give a famous instance of twins who are genetically identical, share identical phenotypes but one is struck by lightening and dies while the other lives and reproduces.
This kind of drift can be crucial in the evolution of a species. It's not the only method of evolution. The primary alternative is a process known as natural selection, where phenotypic variation in an individual is maintained through mutation and migration.
Stephens asserts that there is a vast distinction between treating drift as an actual cause or force, and treating other causes such as selection mutation and migration as forces and causes. He claims that a causal-process account of drift allows us separate it from other forces and that this distinction is essential. He further argues that drift has both direction, i.e., it tends to eliminate heterozygosity. It also has a size which is determined by population size.
Evolution by Lamarckism
When students in high school study biology they are often introduced to the work of Jean-Baptiste Lamarck (1744 - 1829). His theory of evolution is often referred to as "Lamarckism" and it states that simple organisms develop into more complex organisms through the inherited characteristics that result from the organism's natural actions usage, use and disuse. Lamarckism is usually illustrated with the image of a giraffe stretching its neck to reach higher up in the trees. This would cause the necks of giraffes that are longer to be passed on to their offspring who would then grow even taller.
Lamarck the French zoologist, presented an innovative idea in his opening lecture at the Museum of Natural History of Paris. He challenged the traditional thinking about organic transformation. According to Lamarck, living creatures evolved from inanimate material through a series of gradual steps. Lamarck was not the first to propose this but he was thought of as the first to provide the subject a thorough and general overview.
The popular narrative is that Lamarckism was an opponent to Charles Darwin's theory of evolution through natural selection and that the two theories battled out in the 19th century. Darwinism eventually prevailed, leading to what biologists call the Modern Synthesis. The Modern Synthesis theory denies that traits acquired through evolution can be inherited, and instead suggests that organisms evolve through the action of environmental factors, such as natural selection.
While Lamarck endorsed the idea of inheritance by acquired characters, and his contemporaries also paid lip-service to this notion, it was never a major feature in any of their evolutionary theories. This is due to the fact that it was never scientifically tested.
It has been more than 200 years since the birth of Lamarck, and in the age genomics, there is an increasing body of evidence that supports the heritability-acquired characteristics. This is sometimes referred to as "neo-Lamarckism" or more frequently epigenetic inheritance. It is a form of evolution that is as relevant as the more popular Neo-Darwinian theory.
Evolution by Adaptation
One of the most common misconceptions about evolution is being driven by a fight for survival. In fact, this view is a misrepresentation of natural selection and ignores the other forces that determine the rate of evolution. The struggle for survival is more precisely described as a fight to survive within a particular environment, which may include not just other organisms, but as well the physical environment.
Understanding how adaptation works is essential to understand evolution. Adaptation refers to any particular characteristic that allows an organism to survive and reproduce within its environment. It could be a physiological feature, such as fur or feathers, or a behavioral trait like moving into the shade in hot weather or coming out at night to avoid the cold.
The capacity of a living thing to extract energy from its environment and interact with other organisms and their physical environments, is crucial to its survival. The organism must possess the right genes to create offspring and to be able to access enough food and resources. In addition, the organism should be capable of reproducing in a way that is optimally within its niche.
These factors, in conjunction with mutations and gene flow can result in an alteration in the ratio of different alleles in the gene pool of a population. This shift in the frequency of alleles can result in the emergence of novel traits and eventually new species in the course of time.
Many of the characteristics we admire about animals and plants are adaptations, like lung or gills for removing oxygen from the air, fur or feathers to provide insulation long legs to run away from predators and camouflage to hide. To understand the concept of adaptation it is essential to distinguish between behavioral and physiological traits.
Physiological traits like large gills and thick fur are physical traits. The behavioral adaptations aren't, such as the tendency of animals to seek companionship or to retreat into the shade during hot weather. It is also important to note that insufficient planning does not cause an adaptation. Failure to consider the implications of a choice, even if it appears to be rational, may make it inflexible.