What is Free Evolution?
Free evolution is the notion that the natural processes of living organisms can lead them to evolve over time. This includes the evolution of new species as well as the transformation of the appearance of existing species.
This has been proven by numerous examples such as the stickleback fish species that can thrive in saltwater or fresh water and walking stick insect types that have a preference for specific host plants. These typically reversible traits cannot explain fundamental changes to the body's basic plans.
Evolution through Natural Selection
Scientists have been fascinated by the evolution of all living creatures that live on our planet for many centuries. The best-established explanation is Charles Darwin's natural selection, an evolutionary process that occurs when better-adapted individuals survive and reproduce more successfully than those less well adapted. Over time, a community of well adapted individuals grows and eventually becomes a new species.
Natural selection is a cyclical process that involves the interaction of three factors including inheritance, variation, and reproduction. Sexual reproduction and mutations increase genetic diversity in the species. Inheritance refers to the passing of a person's genetic traits to his or her offspring that includes dominant and recessive alleles. Reproduction is the process of generating viable, fertile offspring. This can be accomplished through sexual or asexual methods.
All of these variables must be in balance for natural selection to occur. For example, if a dominant allele at a gene can cause an organism to live and reproduce more frequently than the recessive allele 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 go away. This process is self-reinforcing meaning that the organism with an adaptive trait will survive and reproduce much more than those with a maladaptive feature. The higher the level of fitness an organism has as measured by its capacity to reproduce and survive, is the more offspring it produces. Individuals with favorable characteristics, like having a longer neck in giraffes and bright white color patterns in male peacocks, are more likely to survive and have offspring, and thus will become the majority of the population in the future.
Natural selection is an aspect of populations and not on individuals. This is a crucial distinction from the Lamarckian evolution theory which holds that animals acquire traits either through the use or absence of use. For instance, if a giraffe's neck gets longer through stretching to reach prey its offspring will inherit a larger neck. The differences in neck size between generations will continue to grow until the giraffe becomes unable to reproduce with other giraffes.
Evolution by Genetic Drift
Genetic drift occurs when the alleles of a gene are randomly distributed within a population. In the end, one will reach fixation (become so widespread that it is unable to be removed through natural selection), while other alleles fall to lower frequencies. In the extreme this, it leads to one allele dominance. The other alleles are eliminated, and heterozygosity decreases to zero. In a small population it could result in the complete elimination of the recessive gene. This scenario is called the bottleneck effect and is typical of an evolutionary process that occurs whenever a large number individuals migrate to form a group.
A phenotypic 'bottleneck' can also occur when the survivors of a catastrophe like an outbreak or mass hunting incident are concentrated in an area of a limited size. The surviving individuals will be mostly homozygous for the dominant allele, which means that they will all share the same phenotype and thus share the same fitness characteristics. This situation might be caused by war, an earthquake or even a cholera outbreak. Regardless of the cause 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 the exact same phenotype and yet one is struck by lightening and dies while the other lives and reproduces.
This kind of drift could be vital to the evolution of the species. It's not the only method for evolution. The primary alternative is a process called natural selection, where phenotypic variation in an individual is maintained through mutation and migration.
Stephens argues there is a vast distinction between treating drift as an actual cause or force, and treating other causes like selection mutation and migration as forces and causes. Stephens claims that a causal process account of drift allows us to distinguish it from other forces, and that this distinction is vital. He argues further that drift is both an orientation, i.e., it tends towards eliminating heterozygosity. It also has a size that is determined by the size of the population.
Evolution through Lamarckism
Biology students in high school are frequently introduced to Jean-Baptiste Lamarck's (1744-1829) work. His theory of evolution, often called "Lamarckism which means that simple organisms transform into more complex organisms by taking on traits that result from the use and abuse of an organism. Lamarckism is illustrated through an giraffe's neck stretching to reach higher branches in the trees. This would result in giraffes passing on their longer necks to offspring, who then become taller.
Lamarck was a French zoologist and, in his lecture to begin his course on invertebrate Zoology at the Museum of Natural History in Paris on the 17th of May in 1802, he introduced an original idea that fundamentally challenged the conventional wisdom about organic transformation. According to him living things evolved from inanimate matter through a series of gradual steps. Lamarck was not the first to make this claim, but he was widely thought of as the first to offer the subject a comprehensive and general overview.
The most popular story is that Lamarckism was an opponent to Charles Darwin's theory of evolution through natural selection, and both theories battled out in the 19th century. Darwinism eventually triumphed, leading to the development of what biologists call the Modern Synthesis. This theory denies that traits acquired through evolution can be inherited, and instead, it argues that organisms develop through the selective action of environmental factors, including natural selection.
Although Lamarck endorsed the idea of inheritance by acquired characters, and his contemporaries also spoke of this idea however, it was not a central element in any of their evolutionary theories. This is largely due to the fact that it was never tested scientifically.
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 of acquired traits. This is also known as "neo Lamarckism", or more generally epigenetic inheritance. 에볼루션 블랙잭 is a variant that is as valid as the popular Neodarwinian model.
Evolution by Adaptation
One of the most popular misconceptions about evolution is that it is being driven by a struggle to survive. This is a false assumption and ignores other forces driving evolution. The struggle for survival is more effectively described as a struggle to survive in a specific environment, which may be a struggle that involves not only other organisms, but also the physical environment.
Understanding adaptation is important to comprehend evolution. Adaptation refers to any particular feature that allows an organism to live and reproduce within its environment. It can be a physiological structure, such as fur or feathers or a behavior, such as moving to the shade during hot weather or stepping out at night to avoid cold.
An organism's survival depends on its ability to draw energy from the environment and to interact with other living organisms and their physical surroundings. The organism needs to have the right genes to create offspring, and it must be able to access enough food and other resources. The organism must be able to reproduce at a rate that is optimal for its niche.
These factors, together with gene flow and mutations can result in an alteration in the ratio of different alleles in the gene pool of a population. This shift in the frequency of alleles can lead to the emergence of novel traits and eventually, new species over time.
Many of the characteristics we admire in animals and plants are adaptations. For instance the lungs or gills which extract oxygen from air feathers and fur as insulation and long legs to get away from predators and camouflage to conceal. To understand adaptation it is essential to discern between physiological and behavioral traits.
Physiological adaptations, like the thick fur or gills are physical characteristics, whereas behavioral adaptations, such as the tendency to search for companions or to move to shade in hot weather, are not. In addition, it is important to understand that a lack of thought does not make something an adaptation. A failure to consider the implications of a choice even if it seems to be logical, can make it inflexible.