What is Free Evolution?
Free evolution is the notion that natural processes can cause organisms to develop over time. This includes the appearance and development of new species.
This has been proven by numerous examples, including stickleback fish varieties that can thrive in fresh or saltwater and walking stick insect species that have a preference for particular host plants. These typically reversible traits do not explain the fundamental changes in the basic body plan.
Evolution by Natural Selection
The development of the myriad of living creatures on Earth is a mystery that has intrigued scientists for centuries. Charles Darwin's natural selectivity is the most well-known explanation. This is because people who are more well-adapted have more success in reproduction and survival than those who are less well-adapted. Over time, the population of well-adapted individuals becomes larger and eventually creates an entirely new species.
Natural selection is a cyclical process that involves the interaction of three factors that are inheritance, variation and reproduction. Sexual reproduction and mutation increase the genetic diversity of a species. Inheritance is the transfer of a person's genetic traits to his or her offspring that includes dominant and recessive alleles. Reproduction is the production of fertile, viable offspring which includes both sexual and asexual methods.
All of these factors have to be in equilibrium for natural selection to occur. For instance when an allele that is dominant at the gene can cause an organism to live and reproduce more often than the recessive one, the dominant allele will become more common in the population. If the allele confers a negative survival advantage or reduces the fertility of the population, it will be eliminated. This process is self-reinforcing which means that an organism with an adaptive trait will live and reproduce much more than one with a maladaptive characteristic. The more offspring an organism produces the more fit it is that is determined by its capacity to reproduce itself and live. People with good characteristics, like having a longer neck in giraffes, or bright white patterns of color in male peacocks are more likely to survive and produce offspring, which means they will make up the majority of the population over time.
Natural selection is only a force for populations, not individuals. This is a significant distinction from the Lamarckian theory of evolution, which states that animals acquire traits either through usage or inaction. For instance, if the animal's neck is lengthened by stretching to reach for prey, its offspring will inherit a more long neck. The length difference between generations will continue until the giraffe's neck gets so long that it can no longer breed with other giraffes.
Evolution through Genetic Drift
Genetic drift occurs when alleles of one gene are distributed randomly in a group. At some point, one will attain fixation (become so common that it is unable to be removed by natural selection) and other alleles fall to lower frequencies. In the extreme this, it leads to a single allele dominance. The other alleles are eliminated, and heterozygosity is reduced to zero. In a small number of people, this could lead to the total elimination of recessive alleles. This scenario is called a bottleneck effect, and it is typical of the kind of evolutionary process that takes place when a large amount of individuals migrate to form a new group.
A phenotypic bottleneck could occur when the survivors of a disaster such as an epidemic or a mass hunt, are confined into a small area. The survivors will have an dominant allele, and will share the same phenotype. This can be caused by earthquakes, war or even plagues. The genetically distinct population, if left, could be susceptible to genetic drift.
Walsh Lewens, Lewens, and Ariew use Lewens, Walsh, and Ariew use a "purely outcome-oriented" definition of drift as any departure from the expected values of different fitness levels. They give the famous example of twins that are genetically identical and have exactly the same phenotype. However, one is struck by lightning and dies, while the other is able to reproduce.
This type of drift can play a very important role in the evolution of an organism. However, it is not the only way to develop. Natural selection is the main alternative, in which mutations and migrations maintain the phenotypic diversity in a population.
Stephens claims that there is a vast difference between treating the phenomenon of drift as a force or cause, and considering other causes, such as selection mutation and migration as causes and forces. He claims that a causal mechanism account of drift allows us to distinguish it from these other forces, and this distinction is crucial. He further argues that drift is both an orientation, i.e., it tends to reduce heterozygosity. It also has a size which is determined by the size of the population.
Evolution by Lamarckism
When high school students study biology, they are often introduced to the work of Jean-Baptiste Lamarck (1744 - 1829). His theory of evolution, also referred to as “Lamarckism”, states that simple organisms evolve into more complex organisms adopting traits that are a product of an organism's use and disuse. Lamarckism can be illustrated by an giraffe's neck stretching to reach higher levels of leaves in the trees. This could cause giraffes to pass on their longer necks to offspring, which then become taller.
Lamarck was a French zoologist and, in his inaugural lecture for his course on invertebrate zoology at the Museum of Natural History in Paris on 17 May 1802, he introduced a groundbreaking concept that radically challenged the previous understanding of organic transformation. In his view living things evolved from inanimate matter via a series of gradual steps. Lamarck wasn't the first to suggest this, but he was widely considered to be the first to offer the subject a comprehensive and general explanation.
The most popular story is that Charles Darwin's theory of evolution by natural selection and Lamarckism fought during the 19th century. Darwinism ultimately won which led to what biologists refer to as the Modern Synthesis. This theory denies that acquired characteristics can be inherited and instead argues that organisms evolve through the selective action of environmental factors, such as natural selection.
Lamarck and his contemporaries believed in the idea that acquired characters could be passed on to future generations. However, this idea was never a major part of any of their theories on evolution. This is partly because it was never scientifically tested.
It's been more than 200 year since Lamarck's birth and in the field of age genomics, there is a growing evidence base that supports the heritability acquired characteristics. This is referred to as "neo Lamarckism", or more often epigenetic inheritance. It is a variant of evolution that is just as valid as the more well-known Neo-Darwinian theory.
Evolution by the process of adaptation
One of the most popular misconceptions about evolution is that it is driven by a sort of struggle to survive. 에볼루션사이트 is a false assumption and ignores other forces driving evolution. The struggle for survival is more accurately described as a struggle to survive within a specific environment, which can include not just other organisms, but as well the physical environment.
Understanding adaptation is important to understand evolution. The term "adaptation" refers to any characteristic that allows living organisms to survive in its environment and reproduce. It can be a physiological structure such as fur or feathers, or a behavioral trait, such as moving into shade in hot weather or stepping out at night to avoid the cold.
An organism's survival depends on its ability to extract energy from the surrounding environment and interact with other organisms and their physical environments. The organism must possess the right genes for producing offspring and to be able to access enough food and resources. The organism must be able to reproduce itself at an amount that is appropriate for its particular niche.
These factors, in conjunction with gene flow and mutations can result in changes in the proportion of different alleles within the gene pool of a population. As time passes, this shift in allele frequencies could result in the development of new traits and eventually new species.
A lot of the traits we admire about animals and plants are adaptations, such as the lungs or gills that extract oxygen from the air, fur or feathers for insulation long legs to run away from predators and camouflage for hiding. To understand the concept of adaptation it is crucial to distinguish between behavioral and physiological characteristics.
Physiological adaptations, such as thick fur or gills, are physical traits, whereas behavioral adaptations, like the tendency to search for friends or to move into the shade in hot weather, are not. In addition, it is important to understand that lack of planning is not a reason to make something an adaptation. In fact, failure to think about the implications of a decision can render it ineffective, despite the fact that it may appear to be sensible or even necessary.