What is Free Evolution?
Free evolution is the concept that the natural processes that organisms go through can cause them to develop over time. This includes the appearance and development of new species.
Many examples have been given of this, such as different varieties of fish called sticklebacks that can live in either salt or fresh water, as well as walking stick insect varieties that prefer particular host plants. These are mostly reversible traits however, are not able to be the reason for fundamental changes in body plans.
Evolution through Natural Selection
Scientists have been fascinated by the development of all the living creatures that live on our planet for many centuries. Charles Darwin's natural selection theory is the best-established explanation. This happens when those who are better adapted are able to reproduce faster and longer than those who are less well-adapted. As time passes, a group of well-adapted individuals expands and eventually becomes a new species.
Natural selection is a cyclical process that is characterized by the interaction of three elements that are inheritance, variation and reproduction. Sexual reproduction and mutation increase genetic diversity in the species. Inheritance is the passing of a person's genetic characteristics to the offspring of that person, which includes both dominant and recessive alleles. Reproduction is the generation of viable, fertile offspring, which includes both asexual and sexual methods.
All of these elements must be in balance to allow natural selection to take place. If, for instance the dominant gene allele allows an organism to reproduce and live longer than the recessive allele, then the dominant allele becomes more prevalent in a population. If the allele confers a negative advantage to survival or lowers the fertility of the population, it will go away. The process is self-reinforcing, meaning that a species with a beneficial characteristic will survive and reproduce more than an individual with a maladaptive trait. The greater an organism's fitness, measured by its ability reproduce and survive, is the greater number of offspring it produces. People with good characteristics, such as a long neck in Giraffes, or the bright white color patterns on male peacocks are more likely to others to live and reproduce, which will eventually lead to them becoming the majority.
Natural selection is only an aspect of populations and not on individuals. This is an important distinction from the Lamarckian theory of evolution which states that animals acquire characteristics by use or inactivity. If a giraffe extends its neck to catch prey, and the neck becomes longer, then the children will inherit this characteristic. The difference in neck size between generations will increase until the giraffe is no longer able to breed with other giraffes.
Evolution through Genetic Drift
In the process of genetic drift, alleles at a gene may attain different frequencies in a population through random events. At some point, only one of them will be fixed (become widespread enough to not longer be eliminated through natural selection), and the other alleles diminish in frequency. In the extreme, this leads to dominance of a single allele. The other alleles are essentially eliminated, and heterozygosity falls to zero. In a small group it could lead to the total elimination of recessive alleles. This scenario is known as a bottleneck effect and it is typical of the kind of evolutionary process when a large number of people migrate to form a new group.
A phenotypic bottleneck may happen when the survivors of a catastrophe, such as an epidemic or a mass hunt, are confined into a small area. The survivors will have a dominant allele and thus will share the same phenotype. This situation could be caused by earthquakes, war, or even plagues. The genetically distinct population, if left susceptible to genetic drift.
Walsh, Lewens, and Ariew employ Lewens, Walsh, and Ariew use a "purely outcome-oriented" definition of drift as any deviation from the expected values of variations in fitness. They cite a famous example of twins that are genetically identical, have identical phenotypes, but one is struck by lightening and dies while the other lives and reproduces.
This type of drift is vital to the evolution of an entire species. But, it's not the only method to evolve. The most common alternative is a process known as natural selection, where the phenotypic variation of the population is maintained through mutation and migration.
에볼루션 사이트 argues there is a significant difference between treating the phenomenon of drift as a force or cause, and treating other causes such as migration and selection as forces and causes. He argues that a causal-process model of drift allows us to distinguish it from other forces and that this distinction is crucial. He further argues that drift is a directional force: that is, it tends to eliminate heterozygosity. He also claims that it also has a size, which is determined by the size of the population.
Evolution by Lamarckism
Students of biology in high school are often introduced to Jean-Baptiste Lamarck's (1744-1829) work. His theory of evolution, often referred to as “Lamarckism”, states that simple organisms develop into more complex organisms by taking on traits that result from the organism's use and misuse. Lamarckism is usually illustrated with a picture of a giraffe stretching its neck longer to reach leaves higher up in the trees. This would cause giraffes' longer necks to be passed on to their offspring who would then grow even taller.
Lamarck the French Zoologist, introduced an innovative idea in his 17 May 1802 opening lecture at the Museum of Natural History of Paris. He challenged the conventional wisdom on organic transformation. According to Lamarck, living things evolved from inanimate matter by a series of gradual steps. Lamarck was not the only one to suggest that this could be the case, but the general consensus is that he was the one giving the subject its first broad and comprehensive treatment.
The prevailing story is that Lamarckism grew into a rival to Charles Darwin's theory of evolutionary natural selection, and that the two theories fought each other in the 19th century. Darwinism eventually prevailed, leading to the development of what biologists refer to as the Modern Synthesis. This theory denies acquired characteristics can be passed down through generations and instead, it claims that organisms evolve through the selective influence of environmental elements, like Natural Selection.
Lamarck and his contemporaries supported the notion that acquired characters could be passed on to future generations. However, this concept was never a key element of any of their evolutionary theories. This is largely due to the fact that it was never tested scientifically.
It has been more than 200 year since Lamarck's birth and in the field of genomics, there is a growing evidence base that supports the heritability of acquired traits. This is sometimes called "neo-Lamarckism" or, more commonly epigenetic inheritance. This is a variant that is as valid as the popular Neodarwinian model.
Evolution through adaptation
One of the most commonly-held misconceptions about evolution is that it is being driven by a struggle to survive. In reality, this notion is a misrepresentation of natural selection and ignores the other forces that drive evolution. The fight for survival is better described as a struggle to survive in a particular environment. This can include not only other organisms, but also the physical surroundings themselves.
Understanding the concept of adaptation is crucial to comprehend evolution. It is a feature that allows a living thing to live in its environment and reproduce. It could be a physical feature, such as feathers or fur. It could also be a trait of behavior such as moving towards shade during hot weather, or moving out to avoid the cold at night.
An organism's survival depends on its ability to extract energy from the environment and to interact with other organisms and their physical environments. The organism must possess the right genes to produce offspring and be able find enough food and resources. The organism should also be able to reproduce at the rate that is suitable for its niche.
These factors, together with mutation and gene flow result in an alteration in the percentage of alleles (different varieties of a particular gene) in the gene pool of a population. This change in allele frequency could lead to the development of new traits and eventually new species over time.
Many of the characteristics we appreciate in plants and animals are adaptations. For instance, lungs or gills that extract oxygen from the air, fur and feathers as insulation long legs to run away from predators, and camouflage to hide. To comprehend adaptation it is essential to distinguish between behavioral and physiological characteristics.
Physiological adaptations, such as the thick fur or gills are physical traits, while behavioral adaptations, like the desire to find friends or to move into the shade in hot weather, are not. It is important to remember that a lack of planning does not make an adaptation. In fact, a failure to think about the implications of a choice can render it unadaptive even though it appears to be reasonable or even essential.