What is Free Evolution?
Free evolution is the idea that natural processes can cause organisms to develop over time. This includes the creation of new species as well as the alteration of the appearance of existing ones.
This has been demonstrated by many examples of stickleback fish species that can be found in fresh or saltwater and walking stick insect species that have a preference for specific host plants. These are mostly reversible traits, however, cannot explain fundamental changes in body plans.
Evolution through Natural Selection
Scientists have been fascinated by the development of all the living creatures that inhabit our planet for many centuries. Charles Darwin's natural selectivity is the most well-known explanation. This happens when those who are better adapted survive and reproduce more than those who are less well-adapted. As time passes, the number of well-adapted individuals grows and eventually creates a new species.
Natural selection is an ongoing process that is characterized by the interaction of three factors: variation, inheritance and reproduction. Variation is caused by mutations and sexual reproduction both of which increase the genetic diversity of the species. Inheritance is the passing of a person's genetic characteristics to the offspring of that person, which includes both recessive and dominant alleles. Reproduction is the process of producing fertile, viable offspring which includes both sexual and asexual methods.
All of these elements have to be in equilibrium for natural selection to occur. If, for instance an allele of a dominant gene makes an organism reproduce and last longer than the recessive gene allele The dominant allele becomes more prevalent in a group. If the allele confers a negative survival advantage or reduces the fertility of the population, it will go away. The process is self-reinforced, meaning that a species with a beneficial characteristic is more likely to survive and reproduce than an individual with an inadaptive characteristic. The more fit an organism is as measured by its capacity to reproduce and survive, is the more offspring it produces. People with good traits, like the long neck of giraffes, or bright white patterns on male peacocks are more likely to others to reproduce and survive which eventually leads to them becoming the majority.
Natural selection is an aspect of populations and not on individuals. This is a crucial distinction from the Lamarckian theory of evolution which holds that animals acquire traits due to the use or absence of use. If a giraffe expands its neck in order to catch prey and the neck grows larger, then its offspring will inherit this characteristic. The length difference between generations will persist until the neck of the giraffe becomes too long to no longer breed with other giraffes.
Evolution by Genetic Drift
In the process of genetic drift, alleles of a gene could attain different frequencies in a group by chance events. At some point, one will reach fixation (become so common that it can no longer be removed through natural selection) and the other alleles drop to lower frequencies. This can result in dominance in the extreme. The other alleles are eliminated, and heterozygosity is reduced to zero. In a small number of people this could lead to the complete elimination of the recessive gene. This scenario is called a bottleneck effect, and it is typical of evolutionary process that takes place when a large amount of individuals move to form a new population.
A phenotypic bottleneck could happen when the survivors of a catastrophe like an epidemic or a mass hunting event, are concentrated within a narrow area. The survivors will carry an dominant allele, and will share the same phenotype. This can be caused by war, earthquakes or even plagues. Regardless of the cause the genetically distinct population that remains could be susceptible to genetic drift.
Walsh Lewens and Ariew employ a "purely outcome-oriented" definition of drift as any departure from expected values for different fitness levels. They give the famous example of twins that are genetically identical and share the same phenotype. However one is struck by lightning and dies, while the other is able to reproduce.
This kind of drift can play a significant role in the evolution of an organism. This isn't the only method of evolution. Natural selection is the main alternative, where mutations and migrations maintain the phenotypic diversity in a population.
Stephens argues there is a vast distinction between treating drift as a force or cause, and treating other causes like migration and selection as forces and causes. He argues that a causal-process explanation of drift lets us separate it from other forces, and this distinction is crucial. He also claims that drift has a direction, that is it tends to eliminate heterozygosity, and that it also has a size, that is determined by the size of the population.
Evolution by Lamarckism
Biology students in high school are frequently introduced to Jean-Baptiste Lamarck's (1744-1829) work. His theory of evolution is generally known as "Lamarckism" and it asserts that simple organisms evolve into more complex organisms through the inherited characteristics that result from the natural activities of an organism, use and disuse. Lamarckism is usually illustrated with a picture of a giraffe extending its neck longer to reach higher up in the trees. This causes the necks of giraffes that are longer to be passed onto their offspring who would grow taller.
Lamarck the French Zoologist from France, presented a revolutionary concept in his opening lecture at the Museum of Natural History of Paris. He challenged the previous thinking on organic transformation. According to Lamarck, living things evolved from inanimate material through a series gradual steps. Lamarck was not the first to suggest that this could be the case, but the general consensus is that he was the one giving the subject its first general and comprehensive treatment.
The dominant story is that Charles Darwin's theory of evolution by natural selection and Lamarckism were rivals in the 19th century. Darwinism eventually prevailed and led to what biologists refer to as the Modern Synthesis. The theory argues that acquired traits are passed down from generation to generation and instead, it claims that organisms evolve through the influence of environment factors, such as Natural Selection.
Lamarck and his contemporaries endorsed the idea that acquired characters could be passed on to future generations. However, this idea was never a major part of any of their evolutionary theories. 에볼루션 바카라 is largely due to the fact that it was never validated scientifically.
It has been more than 200 year since Lamarck's birth and in the field of genomics there is a growing body of evidence that supports the heritability acquired characteristics. This is also known as "neo Lamarckism", or more often epigenetic inheritance. This is a model that is as reliable as the popular Neodarwinian model.
Evolution through Adaptation
One of the most popular misconceptions about evolution is its being driven by a struggle to survive. In reality, this notion is inaccurate and overlooks the other forces that drive evolution. The fight for survival can be more accurately described as a struggle to survive within a specific environment, which could include not just other organisms but as well the physical environment.
To understand how evolution works it is important to understand what is adaptation. Adaptation refers to any particular feature that allows an organism to live and reproduce in its environment. It could be a physiological feature, such as feathers or fur or a behavioral characteristic, such as moving into shade in hot weather or coming out at night to avoid cold.
The survival of an organism is dependent on its ability to draw energy from the environment and interact with other organisms and their physical environments. The organism must have the right genes for producing offspring and to be able to access sufficient food and resources. The organism should also be able to reproduce itself at the rate that is suitable for its specific niche.
These factors, together with gene flow and mutations can cause changes in the proportion of different alleles within a population’s gene pool. The change in frequency of alleles could lead to the development of new traits and eventually, new species over time.
Many of the characteristics we appreciate in animals and plants are adaptations. For example, lungs or gills that extract oxygen from the air feathers and fur for insulation and long legs to get away from predators, and camouflage to hide. However, a proper understanding of adaptation requires a keen eye to the distinction between the physiological and behavioral characteristics.
Physiological adaptations, such as thick fur or gills, are physical traits, while behavioral adaptations, like the tendency to search for friends or to move into the shade in hot weather, aren't. It is also important to remember that a the absence of planning doesn't result in an adaptation. In fact, failing to think about the consequences of a choice can render it unadaptable even though it might appear reasonable or even essential.