What is 에볼루션 룰렛 ?
Free evolution is the notion that the natural processes that organisms go through can lead them to evolve over time. This includes the evolution of new species and the alteration of the appearance of existing species.
A variety of examples have been provided of this, including various varieties of stickleback fish that can live in either salt or fresh water, as well as walking stick insect varieties that prefer particular host plants. These typically reversible traits are not able to explain fundamental changes to basic body plans.
Evolution through Natural Selection
The evolution of the myriad living creatures on Earth is a mystery that has fascinated scientists for decades. The most widely accepted explanation is Charles Darwin's natural selection, a process that occurs when better-adapted individuals survive and reproduce more effectively than those less well-adapted. Over time, the population of individuals who are well-adapted grows and eventually forms a new species.
Natural selection is an ongoing process and involves the interaction of three factors including reproduction, variation and inheritance. Variation is caused by mutations and sexual reproduction, both of which increase the genetic diversity of an animal species. Inheritance is the passing of a person's genetic traits to his or her offspring which includes both dominant and recessive alleles. Reproduction is the process of generating fertile, viable offspring. This can be done through sexual or asexual methods.
All of these elements must be in harmony to allow natural selection to take place. For example when an allele that is dominant at the gene causes an organism to survive and reproduce more frequently than the recessive one, the dominant allele will be more prevalent in the population. If the allele confers a negative survival advantage or lowers the fertility of the population, it will disappear. The process is self-reinforced, which means that an organism with a beneficial characteristic is more likely to survive and reproduce than one with an unadaptive characteristic. The more offspring an organism can produce the better its fitness which is measured by its capacity to reproduce itself and live. People with good traits, like a long neck in the giraffe, or bright white color patterns on male peacocks are more likely than others to reproduce and survive and eventually lead to them becoming the majority.
Natural selection is only a force for populations, not individuals. This is a significant distinction from the Lamarckian theory of evolution, which claims that animals acquire characteristics through use or disuse. For instance, if the giraffe's neck gets longer through stretching to reach for prey its offspring will inherit a longer neck. The length difference between generations will persist until the giraffe's neck gets too long that it can not breed with other giraffes.
Evolution through Genetic Drift
Genetic drift occurs when the alleles of one gene are distributed randomly in a population. At some point, only one of them will be fixed (become widespread enough to not more be eliminated through natural selection), and the other alleles will diminish in frequency. This could lead to an allele that is dominant at the extreme. The other alleles have been basically eliminated and heterozygosity has decreased to zero. In a small number of people this could result in the total elimination of recessive alleles. This is known as a bottleneck effect and it is typical of the kind of evolutionary process that occurs when a large number of individuals migrate to form a new population.
A phenotypic bottleneck could occur when the survivors of a disaster like an epidemic or a mass hunting event, are condensed within a narrow area. The survivors will share an dominant allele, and will share the same phenotype. This could be the result of a conflict, earthquake, or even a plague. Whatever the reason the genetically distinct group that remains is susceptible to genetic drift.
Walsh, Lewens and Ariew define drift as a departure from the expected value due to differences in fitness. They cite a famous instance of twins who are genetically identical and have the exact same phenotype and yet one is struck by lightening and dies while the other lives and reproduces.
This kind of drift can be crucial in the evolution of an entire species. However, it's not the only way to evolve. Natural selection is the primary alternative, where mutations and migration maintain the phenotypic diversity in the population.
Stephens claims that there is a significant distinction between treating drift as a force or cause, and treating other causes like migration and selection as forces and causes. He claims that a causal-process account of drift allows us distinguish it from other forces, and this distinction is crucial. He argues further that drift has an orientation, i.e., it tends to reduce heterozygosity. It also has a size, which is determined by the size of the population.
Evolution through Lamarckism
In high school, students study biology they are often introduced to the work of Jean-Baptiste Lamarck (1744 - 1829). His theory of evolution is often called "Lamarckism" and it asserts that simple organisms evolve into more complex organisms through the inherited characteristics that are a result of the natural activities of an organism use and misuse. Lamarckism can be illustrated by the giraffe's neck being extended to reach higher levels of leaves in the trees. This could result in giraffes passing on their longer necks to offspring, which then grow even taller.
Lamarck was a French Zoologist. In his lecture to begin his course on invertebrate zoology at the Museum of Natural History in Paris on the 17th of May in 1802, he introduced a groundbreaking concept that radically challenged the conventional wisdom about organic transformation. According Lamarck, living organisms evolved from inanimate material through a series gradual steps. Lamarck wasn't the first to make this claim, but he was widely thought of as the first to provide the subject a thorough and general overview.
The most popular story is that Charles Darwin's theory on evolution by natural selection and Lamarckism fought in the 19th Century. Darwinism ultimately prevailed which led to what biologists call the Modern Synthesis. This theory denies acquired characteristics can be passed down through generations and instead argues that organisms evolve through the influence of environment elements, like Natural Selection.
Although Lamarck endorsed the idea of inheritance by acquired characters and his contemporaries offered a few words about this idea however, it was not a central element in any of their evolutionary theorizing. This is largely due to the fact that it was never tested scientifically.
However, it has been more than 200 years since Lamarck was born and in the age of genomics, there is a large amount of evidence to support the heritability of acquired traits. This is also known as "neo Lamarckism", or more generally epigenetic inheritance. This is a model that is as valid as the popular neodarwinian model.
Evolution through adaptation
One of the most popular misconceptions about evolution is that it is being driven by a struggle to survive. This view is inaccurate and overlooks other forces that drive evolution. The fight for survival can be better described as a struggle to survive in a certain environment. This can include not only other organisms but also the physical environment.
To understand how evolution functions it is important to think about what adaptation is. It is a feature that allows a living organism to survive in its environment and reproduce. It could be a physiological structure like feathers or fur, or a behavioral trait, such as moving to the shade during hot weather or coming out at night to avoid cold.
The capacity of an organism to extract energy from its environment and interact with other organisms and their physical environments is essential to its survival. The organism must have the right genes to produce offspring and to be able to access sufficient food and resources. The organism should be able to reproduce itself at the rate that is suitable for its niche.
These elements, in conjunction with gene flow and mutation, lead to changes in the ratio of alleles (different forms of a gene) in the gene pool of a population. As time passes, this shift in allele frequencies can lead to the emergence of new traits, and eventually new species.
Many of the features we admire in animals and plants are adaptations. For instance the lungs or gills which draw oxygen from air feathers and fur as insulation and long legs to get away from predators and camouflage for hiding. To understand adaptation it is crucial to differentiate between physiological and behavioral traits.
Physiological adaptations, like thick fur or gills are physical traits, whereas behavioral adaptations, such as the desire to find companions or to move to shade in hot weather, aren't. It is important to note that insufficient planning does not make an adaptation. A failure to consider the consequences of a decision even if it seems to be rational, may make it unadaptive.