What is Free Evolution?
Free evolution is the concept that natural processes can lead to the development of organisms over time. This includes the appearance and development of new species.
Numerous examples have been offered of this, including different varieties of stickleback fish that can live in either fresh or salt water and walking stick insect varieties that are attracted to specific host plants. These mostly reversible traits permutations cannot explain fundamental changes to the body's basic plans.
Evolution by Natural Selection
Scientists have been fascinated by the development of all living creatures that live on our planet for centuries. Charles Darwin's natural selectivity is the most well-known explanation. This is because those who are better adapted survive and reproduce more than those who are 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 that involves the interaction of three elements that are inheritance, variation and reproduction. Variation is caused by mutation and sexual reproduction both of which increase the genetic diversity of an animal species. Inheritance is the term used to describe the transmission of a person's genetic characteristics, which includes recessive and dominant genes, to their offspring. Reproduction is the process of producing fertile, viable offspring which includes both asexual and sexual methods.
All of these variables must be in balance to allow natural selection to take place. For instance when a dominant allele at the gene can cause an organism to live and reproduce more often than the recessive allele the dominant allele will be more common within the population. If the allele confers a negative advantage to survival or decreases the fertility of the population, it will be eliminated. This process is self-reinforcing meaning that an organism that has a beneficial trait will survive and reproduce more than one with an inadaptive characteristic. The more offspring an organism can produce the better its fitness, which is measured by its capacity to reproduce itself and survive. Individuals with favorable traits, like the long neck of giraffes, or bright white patterns on male peacocks are more likely to others to live and reproduce 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 states that animals acquire traits through usage or inaction. For instance, if a Giraffe's neck grows longer due to stretching to reach for prey and its offspring will inherit a more long neck. The difference in neck size between generations will continue to grow until the giraffe becomes unable to breed with other giraffes.
Evolution through Genetic Drift
In genetic drift, alleles at a gene may attain different frequencies within a population due to random events. In the end, one will attain fixation (become so widespread that it is unable to be eliminated through natural selection), while other alleles fall to lower frequency. In extreme cases this, it leads to a single allele dominance. The other alleles are virtually eliminated and heterozygosity diminished to zero. In a small number of people this could lead to the complete elimination of the recessive gene. This scenario is known as a bottleneck effect and it is typical of evolutionary process when a large number of individuals migrate to form a new population.
A phenotypic bottleneck may occur when the survivors of a disaster such as an epidemic or mass hunt, are confined in a limited area. The survivors will share an dominant allele, and will share the same phenotype. This could be caused by war, earthquakes or even a plague. Whatever the reason the genetically distinct group that remains is prone to genetic drift.
Walsh Lewens, Walsh, and Ariew define drift as a departure from the expected values due to differences in fitness. They cite a famous example of twins that are genetically identical and have identical phenotypes, but one is struck by lightening and dies while the other lives and reproduces.
This type of drift is very important in the evolution of a species. This isn't the only method of evolution. Natural selection is the most common alternative, in which mutations and migrations maintain the phenotypic diversity in the population.
Stephens asserts that there is a huge difference between treating drift like a force or cause, and treating other causes like migration and selection as forces and causes. He argues that a causal mechanism account of drift allows us to distinguish it from these other forces, and that this distinction is crucial. He also argues that drift is both a direction, i.e., it tends to reduce heterozygosity. It also has a size, which is determined by population size.
Evolution through Lamarckism
When high school students study biology, they are often introduced to the work of Jean-Baptiste Lamarck (1744 - 1829). His theory of evolution, often referred to as “Lamarckism”, states that simple organisms develop into more complex organisms inheriting characteristics that are a product of the use and abuse of an organism. Lamarckism is typically illustrated with the image of a giraffe stretching its neck further to reach the higher branches in the trees. This would cause giraffes to give their longer necks to their offspring, which then get taller.
Lamarck Lamarck, a French zoologist, presented an idea that was revolutionary in his opening lecture at the Museum of Natural History of Paris. He challenged the traditional thinking about organic transformation. In his view living things had evolved from inanimate matter via a series of gradual steps. Lamarck was not the first to suggest that this could be the case but his reputation is widely regarded as giving the subject its first general and comprehensive treatment.
The popular narrative is that Lamarckism became a rival to Charles Darwin's theory of evolutionary natural selection, and both theories battled each other in the 19th century. Darwinism ultimately prevailed and led to what biologists refer to as the Modern Synthesis. The theory denies that acquired characteristics can be passed down and instead, it claims that organisms evolve through the selective influence of environmental elements, like Natural Selection.
Lamarck and his contemporaries believed in the notion that acquired characters could be passed on to the next generation. However, this concept was never a central part of any of their evolutionary theories. 에볼루션 is partly due to the fact that it was never validated scientifically.
It has been more than 200 years since the birth of Lamarck and in the field of age genomics there is a growing evidence-based body of evidence to support the heritability acquired characteristics. This is referred to as "neo Lamarckism", or more commonly epigenetic inheritance. It is a variant of evolution that is just as valid as the more popular neo-Darwinian model.
Evolution by the process of adaptation
One of the most commonly-held misconceptions about evolution is its being driven by a fight for survival. In reality, this notion is a misrepresentation of natural selection and ignores the other forces that are driving evolution. The fight for survival can be more precisely described as a fight to survive within a particular environment, which could include not just other organisms but also the physical environment.
Understanding the concept of adaptation is crucial to comprehend evolution. Adaptation refers to any particular characteristic that allows an organism to survive and reproduce within its environment. It could be a physical structure such as feathers or fur. It could also be a behavior trait, like moving towards shade during hot weather or moving out to avoid the cold at night.
The survival of an organism depends on its ability to obtain energy from the surrounding environment and interact with other organisms and their physical environments. The organism should possess the right genes for producing offspring, and be able to find enough food and resources. The organism should also be able to reproduce at the rate that is suitable for its specific niche.
These elements, along with mutations and gene flow can result in a shift in the proportion of different alleles in the gene pool of a population. The change in frequency of alleles can lead to the emergence of new traits, and eventually new species over time.
A lot of the traits we appreciate in animals and plants are adaptations. For instance lung 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 thorough understanding of adaptation requires paying attention to the distinction between behavioral and physiological characteristics.
Physical characteristics like thick fur and gills are physical traits. Behavioral adaptations are not like the tendency of animals to seek companionship or move into the shade during hot temperatures. It is also important to note that insufficient planning does not make an adaptation. Inability to think about the effects of a behavior even if it appears to be rational, could cause it to be unadaptive.