What is Free Evolution?
Free evolution is the notion that the natural processes that organisms go through can lead them to evolve over time. This includes the appearance and development of new species.
A variety of examples have been provided of this, including various kinds of stickleback fish that can live in either salt or fresh water, and walking stick insect varieties that are attracted to particular host plants. These mostly reversible trait permutations however, are not able to explain fundamental changes in basic body plans.
Evolution by Natural Selection
The evolution of the myriad living creatures on Earth is an enigma that has fascinated scientists for centuries. Charles Darwin's natural selection theory is the most well-known explanation. This process occurs when people who are more well-adapted have more success in reproduction and survival than those who are less well-adapted. As time passes, the number of well-adapted individuals becomes larger and eventually forms an entirely new species.
Natural selection is an ongoing process and involves the interaction of three factors that are: reproduction, variation and inheritance. Variation is caused by mutations and sexual reproduction both of which enhance the genetic diversity of an animal species. Inheritance is the transfer of a person's genetic traits to their offspring that includes recessive and dominant alleles. Reproduction is the process of generating viable, fertile offspring. This can be done through sexual or asexual methods.
Natural selection can only occur when all the factors are in balance. If, for example, a dominant gene allele makes an organism reproduce and live longer than the recessive gene The dominant allele is more common in a population. If the allele confers a negative advantage to survival or decreases the fertility of the population, it will disappear. This process is self-reinforcing meaning that a species with a beneficial characteristic will survive and reproduce more than an individual with an inadaptive trait. The more offspring that an organism has the better its fitness which is measured by its capacity to reproduce itself and live. People with good characteristics, such as having a long neck in giraffes, or bright white patterns on male peacocks, are more likely than others to survive and reproduce, which will eventually lead to them becoming the majority.
Natural selection only acts on populations, not individual organisms. This is a major distinction from the Lamarckian theory of evolution, which claims that animals acquire traits through use or disuse. For instance, if the giraffe's neck gets longer through reaching out to catch prey and its offspring will inherit a longer neck. The differences in neck size between generations will increase until the giraffe is no longer able to reproduce with other giraffes.
Evolution through Genetic Drift
In the process of genetic drift, alleles within a gene can reach different frequencies in a group by chance events. Eventually, only one will be fixed (become widespread enough to not longer be eliminated through natural selection), and the other alleles decrease in frequency. This can lead to dominance in the extreme. The other alleles are essentially eliminated, and heterozygosity decreases to zero. In a small group, this could result in the complete elimination of the recessive gene. This is known as a bottleneck effect and it is typical of evolutionary process when a large number of people migrate to form a new population.
A phenotypic 'bottleneck' can also occur when survivors of a disaster such as an outbreak or mass hunting event are concentrated in the same area. The surviving individuals will be largely homozygous for the dominant allele, meaning that they all share the same phenotype and therefore have the same fitness traits. This can be caused by war, earthquakes or even a plague. Regardless of the cause the genetically distinct group that remains is susceptible to genetic drift.
Walsh, Lewens, and Ariew utilize a "purely outcome-oriented" definition of drift as any deviation from expected values for differences in fitness. 에볼루션 룰렛 cite a famous instance of twins who are genetically identical, share identical phenotypes, and yet one is struck by lightning and dies, whereas the other lives and reproduces.
This kind of drift could play a very important role in the evolution of an organism. It is not the only method of evolution. Natural selection is the main alternative, where mutations and migrations maintain the phenotypic diversity in a population.
Stephens claims that there is a significant difference between treating the phenomenon of drift as a force or as an underlying cause, and considering other causes of evolution such as selection, mutation and migration as forces or causes. Stephens claims that a causal process model of drift allows us to distinguish it from other forces and that this distinction is essential. He further argues that drift has an orientation, i.e., it tends to reduce heterozygosity. It also has a size, which is determined by population size.
Evolution through Lamarckism
Biology students in high school are frequently introduced to Jean-Baptiste Lemarck's (1744-1829) work. His theory of evolution is generally referred to as "Lamarckism" and it asserts that simple organisms evolve into more complex organisms by the inheritance of traits which result from an organism's natural activities usage, use and disuse. Lamarckism is typically illustrated with a picture of a giraffe stretching its neck further to reach leaves higher up in the trees. This would cause giraffes' longer necks to be passed onto their offspring who would grow taller.
Lamarck the French Zoologist from France, presented a revolutionary concept in his opening lecture at the Museum of Natural History of Paris. He challenged the conventional wisdom on organic transformation. According to Lamarck, living things evolved from inanimate material through a series gradual steps. Lamarck was not the first to suggest this, but he was widely thought of as the first to provide the subject a thorough and general treatment.
The prevailing story is that Lamarckism grew into an opponent to Charles Darwin's theory of evolution through natural selection and that the two theories fought it out in the 19th century. Darwinism eventually triumphed and led to the development of what biologists now call the Modern Synthesis. The theory argues that acquired traits are passed down from generation to generation and instead, it claims that organisms evolve through the influence of environment elements, like Natural Selection.
While Lamarck endorsed the idea of inheritance through acquired characters and his contemporaries paid lip-service to this notion but it was not a central element in any of their evolutionary theories. This is due to the fact that it was never scientifically tested.
It's been more than 200 years since the birth of Lamarck, and in the age genomics, there is a growing body of evidence that supports the heritability acquired characteristics. This is sometimes referred to as "neo-Lamarckism" or, more commonly epigenetic inheritance. It is a version of evolution that is just as valid as the more popular Neo-Darwinian model.
Evolution by adaptation
One of the most popular misconceptions about evolution is its being driven by a fight for survival. This view is a misrepresentation of natural selection and ignores the other forces that drive evolution. The fight for survival can be better described as a struggle to survive in a specific environment. This may include not only other organisms as well as the physical environment itself.
Understanding the concept of adaptation is crucial to understand evolution. The term "adaptation" refers to any specific feature that allows an organism to survive and reproduce in its environment. It could be a physical structure like feathers or fur. Or it can be a characteristic of behavior, like moving into the shade during hot weather, or moving out to avoid the cold at night.
The capacity of a living thing to extract energy from its surroundings and interact with other organisms and their physical environment, is crucial to its survival. The organism must possess the right genes to generate offspring, and must be able to access sufficient food and other resources. In addition, the organism should be capable of reproducing itself at an optimal rate within its environment.
These factors, together with mutation and gene flow result in changes in the ratio of alleles (different forms of a gene) in the population's gene pool. This shift in the frequency of alleles could lead to the development of novel traits and eventually, new species over time.
A lot of the traits we admire in plants and animals are adaptations. For instance lung or gills that extract oxygen from the air feathers and fur for insulation and long legs to get away from predators and camouflage to conceal. However, a proper understanding of adaptation requires attention to the distinction between physiological and behavioral characteristics.
Physiological adaptations, such as thick fur or gills are physical characteristics, whereas behavioral adaptations, such as the tendency to search for companions or to retreat into the shade in hot weather, aren't. It is important to keep in mind that lack of planning does not cause an adaptation. Failure to consider the effects of a behavior even if it appears to be rational, may cause it to be unadaptive.