What is Free Evolution?
Free evolution is the idea that natural processes can cause organisms to evolve over time. This includes the appearance and development of new species.
This has been demonstrated by numerous examples such as the stickleback fish species that can live in salt or fresh water, and walking stick insect types that are apprehensive about specific host plants. These mostly reversible traits permutations are not able to explain fundamental changes to the body's basic plans.
Evolution by Natural Selection
The development of the myriad of living organisms on Earth is an enigma that has fascinated scientists for centuries. The most well-known explanation is Charles Darwin's natural selection, a process that occurs when better-adapted individuals survive and reproduce more effectively than those that are less well-adapted. Over time, the population of individuals who are well-adapted grows and eventually forms an entirely new species.
Natural selection is a process that is cyclical 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 within the species. Inheritance is the term used to describe the transmission of genetic traits, including recessive and dominant genes to their offspring. Reproduction is the production of fertile, viable offspring, which includes both asexual and sexual methods.
All of these elements must be in harmony to allow natural selection to take place. If, for instance an allele of a dominant gene allows an organism to reproduce and survive more than the recessive gene allele then the dominant allele becomes more common in a population. However, if the gene confers a disadvantage in survival or reduces fertility, it will be eliminated from the population. This process is self-reinforcing meaning that an organism that has an adaptive trait will live and reproduce far more effectively than those with a maladaptive trait. The more offspring an organism can produce the more fit it is that is determined by its ability to reproduce and survive. People with desirable traits, like the long neck of giraffes, or bright white patterns on male peacocks, are more likely than others to live and reproduce and eventually lead to them becoming the majority.
Natural selection only acts on populations, not individual organisms. This is a crucial distinction from the Lamarckian evolution theory which holds that animals acquire traits through the use or absence of use. If a giraffe extends its neck to reach prey and the neck grows larger, then its offspring will inherit this characteristic. The difference in neck size between generations will continue to increase until the giraffe becomes unable to reproduce with other giraffes.
Evolution through Genetic Drift
In the process of genetic drift, alleles at a gene may attain different frequencies in a group by chance events. Eventually, only one will be fixed (become widespread enough to not longer be eliminated by natural selection), and the rest of the alleles will drop in frequency. In the extreme, this leads to one allele dominance. The other alleles are basically eliminated and heterozygosity has diminished to zero. In a small group it could lead to the total elimination of recessive allele. This is known as the bottleneck effect and is typical of the evolutionary process that occurs when the number of individuals migrate to form a group.
A phenotypic bottleneck can also happen when the survivors of a catastrophe, such as an epidemic or a massive hunt, are confined within a narrow area. The survivors will carry an allele that is dominant and will share the same phenotype. This situation could be caused by war, earthquakes 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 expected values due to differences in fitness. They give a famous example of twins that are genetically identical, share identical phenotypes, and yet one is struck by lightning and dies, while the other lives and reproduces.
This kind of drift could play a significant role in the evolution of an organism. It's not the only method for evolution. Natural selection is the most common alternative, in which mutations and migration keep 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 such as migration and selection as forces and causes. He argues that a causal-process model of drift allows us to differentiate it from other forces and that this distinction is crucial. He also claims that drift has a direction: that is, it tends to eliminate heterozygosity. It also has a specific magnitude that is determined by the size of 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, commonly referred to as "Lamarckism is based on the idea that simple organisms transform into more complex organisms through taking on traits that are a product of an organism's use and disuse. Lamarckism is typically illustrated with an image of a giraffe extending its neck longer to reach leaves higher up in the trees. This could cause the longer necks of giraffes to be passed on to their offspring who would then become taller.
Lamarck Lamarck, a French zoologist, presented a revolutionary concept in his 17 May 1802 opening lecture at the Museum of Natural History of Paris. He challenged traditional thinking about organic transformation. According Lamarck, living organisms evolved from inanimate material by a series of gradual steps. Lamarck was not the first to make this claim but he was thought of as the first to provide the subject a thorough and general treatment.
The predominant story is that Charles Darwin's theory on evolution by natural selection and Lamarckism were competing in the 19th Century. 에볼루션 won and led to what biologists call the Modern Synthesis. The Modern Synthesis theory denies that acquired characteristics can be acquired through inheritance and instead, it argues that organisms develop through the selective action of environmental factors, including natural selection.
While Lamarck believed in the concept of inheritance by acquired characters and his contemporaries also spoke of this idea however, it was not an integral part of any of their theories about evolution. 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 of genomics there is a huge amount of evidence to support the possibility of inheritance of acquired traits. This is also known as "neo Lamarckism", or more often epigenetic inheritance. This is a variant that is as valid as the popular neodarwinian model.
Evolution by the process of adaptation
One of the most popular misconceptions about evolution is its being driven by a struggle for survival. This view misrepresents natural selection and ignores the other forces that drive evolution. The struggle for survival is more precisely described as a fight to survive in a specific environment, which can involve not only other organisms but as well the physical environment.
To understand how evolution operates, it is helpful to think about what adaptation is. The term "adaptation" refers to any specific characteristic that allows an organism to live and reproduce within its environment. It could be a physical structure, like feathers or fur. Or it can be a characteristic of behavior such as moving into the shade during the heat, or coming out to avoid the cold at night.
The survival of an organism is dependent 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 to create offspring, and be able to find sufficient food and resources. Moreover, the organism must be capable of reproducing itself at an optimal rate within its environment.
These factors, together with gene flow and mutation result in changes in the ratio of alleles (different types of a gene) in a population's gene pool. The change in frequency of alleles can lead to the emergence of novel traits and eventually new species as time passes.
A lot of the traits we admire in plants and animals are adaptations. For instance lung or gills that draw oxygen from air, fur and feathers as insulation long legs to run away from predators and camouflage to conceal. However, a thorough understanding of adaptation requires paying attention to the distinction between the physiological and behavioral characteristics.
Physical traits such as thick fur and gills are physical traits. The behavioral adaptations aren't an exception, for instance, the tendency of animals to seek out companionship or to retreat into the shade in hot temperatures. In addition it is important to understand that a lack of thought does not make something an adaptation. Failure to consider the consequences of a decision even if it seems to be rational, could make it unadaptive.