What is Free Evolution?
Free evolution is the notion that the natural processes of living organisms can cause them to develop over time. This includes the appearance and development of new species.
Many examples have been given of this, including various varieties of stickleback fish that can live in fresh or salt water and walking stick insect varieties that favor specific host plants. These mostly reversible trait permutations, however, cannot be the reason for fundamental changes in body plans.
Evolution through Natural Selection
The development of the myriad living creatures on Earth is an enigma that has intrigued scientists for centuries. The best-established explanation is Charles Darwin's natural selection process, which occurs when individuals that are better adapted survive and reproduce more successfully than those that are less well adapted. As time passes, the number of individuals who are well-adapted grows and eventually creates an entirely new species.
Natural selection is a cyclical process that involves the interaction of three factors: variation, inheritance and reproduction. Variation is caused by mutation and sexual reproduction both of which enhance the genetic diversity within a 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 producing viable, fertile offspring. This can be achieved via sexual or asexual methods.
Natural selection can only occur when all these elements are in harmony. For example, if an allele that is dominant at one gene allows 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 lowers the fertility of the population, it will disappear. The process is self-reinforcing which means that the organism with an adaptive characteristic will live and reproduce much more than one with a maladaptive characteristic. The more offspring that an organism has the better its fitness, which is measured by its ability to reproduce and survive. Individuals with favorable characteristics, like having a longer neck in giraffes or bright white colors in male peacocks are more likely survive and produce offspring, and thus will eventually 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 claims that animals acquire traits through use or neglect. If a giraffe stretches its neck to catch prey, and the neck becomes longer, then its offspring will inherit this trait. The difference in neck length between generations will persist until the neck of the giraffe becomes too long to not breed with other giraffes.
Evolution through Genetic Drift
Genetic drift occurs when the alleles of one gene are distributed randomly in a group. Eventually, only one will be fixed (become widespread enough to not more be eliminated through natural selection), and the other alleles will drop in frequency. In extreme cases it can lead to a single allele dominance. The other alleles are virtually eliminated and heterozygosity been reduced to zero. In a small population, this could result in the complete elimination the recessive gene. This is called a bottleneck effect, and it is typical of evolutionary process that occurs when a large number of individuals move to form a new population.
에볼루션 무료 바카라 can also occur when survivors of a disaster, such as an epidemic or a mass hunting event, are concentrated within a narrow area. The survivors will be mostly homozygous for the dominant allele which means that they will all share the same phenotype, and therefore share the same fitness characteristics. This could 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 define drift as a departure from expected values due to differences in fitness. They give the famous example of twins who are both genetically identical and share the same phenotype, but one is struck by lightning and dies, whereas the other is able to reproduce.
This kind of drift could play a very important part in the evolution of an organism. However, it's not the only way to develop. The most common alternative is a process called natural selection, where the phenotypic diversity of a population is maintained by mutation and migration.
Stephens argues there is a significant difference between treating drift like an actual cause or force, and treating other causes like selection mutation and migration as forces and causes. He argues that a causal-process account of drift allows us distinguish it from other forces and this distinction is crucial. He also argues that drift is a directional force: that is, it tends to eliminate heterozygosity. He also claims that it also has a magnitude, that is determined by the size of the population.
Evolution by Lamarckism
Students of biology in high school are often introduced to Jean-Baptiste Lemarck's (1744-1829) work. His theory of evolution is commonly referred to as "Lamarckism" and it states that simple organisms develop into more complex organisms via the inheritance of traits which result from the organism's natural actions use and misuse. Lamarckism is illustrated through the giraffe's neck being extended to reach higher leaves in the trees. This would cause giraffes to give their longer necks to their offspring, which then get taller.
Lamarck Lamarck, a French Zoologist from France, 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 things evolved from inanimate matter by a series of gradual steps. Lamarck wasn't the first to suggest this however he was widely considered to be the first to offer the subject a thorough and general explanation.
The predominant story is that Charles Darwin's theory on natural selection and Lamarckism were rivals in the 19th century. Darwinism eventually prevailed and led to the development of what biologists refer to as the Modern Synthesis. The theory argues that acquired traits can be passed down through generations and instead argues organisms evolve by the selective influence of environmental elements, like Natural Selection.
While Lamarck supported the notion of inheritance by acquired characters and his contemporaries also paid lip-service to this notion, it was never an integral part of any of their evolutionary theorizing. This is largely due to the fact that it was never validated scientifically.
However, it has been more than 200 years since Lamarck was born and in the age genomics there is a vast amount of evidence to support the possibility of inheritance of acquired traits. It is sometimes called "neo-Lamarckism" or, more often epigenetic inheritance. It is a form of evolution that is as valid as the more well-known Neo-Darwinian theory.
Evolution through Adaptation
One of the most widespread misconceptions about evolution is that it is a result of a kind of struggle to survive. This notion is not true and overlooks other forces that drive evolution. The fight for survival can be more effectively described as a struggle to survive in a specific environment, which can involve not only other organisms, but as well the physical environment.
Understanding adaptation is important to understand evolution. It is a feature that allows living organisms to live in its environment and reproduce. It can be a physiological structure like feathers or fur or a behavioral characteristic, such as moving into shade in hot weather or stepping out at night to avoid cold.
The survival of an organism is dependent on its ability to extract energy from the surrounding environment and interact with other organisms and their physical environments. The organism must have the right genes to produce offspring, and it should be able to find enough food and other resources. The organism should be able to reproduce itself at a rate that is optimal for its specific niche.
These factors, in conjunction with gene flow and mutations, can lead to changes in the proportion 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 as time passes.
Many of the characteristics we admire in animals and plants are adaptations. For example, lungs or gills that extract oxygen from air, fur and feathers as insulation long legs to run away from predators and camouflage for hiding. However, a complete understanding of adaptation requires a keen eye to the distinction between behavioral and physiological characteristics.
Physiological traits like the thick fur and gills are physical characteristics. The behavioral adaptations aren't, such as the tendency of animals to seek out companionship or move into the shade during hot weather. Furthermore, it is important to understand that a lack of forethought is not a reason to make something an adaptation. Failure to consider the effects of a behavior even if it appears to be rational, may make it unadaptive.