What is Free Evolution?
Free evolution is the concept that natural processes can cause organisms to evolve over time. This includes the appearance and growth of new species.
This has been demonstrated by numerous examples of stickleback fish species that can be found in salt or fresh water, and walking stick insect types that are apprehensive about particular host plants. These mostly reversible trait permutations however, are not able to explain fundamental changes in body plans.
Evolution by Natural Selection
Scientists have been fascinated by the development of all living organisms that inhabit our planet for many centuries. Charles Darwin's natural selection is the most well-known explanation. This process occurs when those who are better adapted survive and reproduce more than those who are less well-adapted. Over time, a population of well-adapted individuals increases and eventually becomes a new species.
Natural selection is an ongoing process that involves the interaction of three factors including inheritance, variation, and reproduction. Variation is caused by mutations and sexual reproduction both of which increase the genetic diversity within an animal 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 producing viable, fertile offspring. This can be accomplished through sexual or asexual methods.
All of these factors have to be in equilibrium to allow natural selection to take place. If, for instance, a dominant gene allele causes an organism reproduce and survive more than the recessive gene allele, then the dominant allele will become more prevalent in a population. If the allele confers a negative advantage to survival or lowers the fertility of the population, it will disappear. The process is self-reinforcing, meaning that an organism with a beneficial characteristic is more likely to survive and reproduce than one with a maladaptive characteristic. The more fit an organism is, measured by its ability reproduce and survive, is the greater number of offspring it produces. Individuals with favorable traits, like longer necks in giraffes, or bright white color patterns in male peacocks, are more likely to be able to survive and create offspring, so they will make up the majority of the population in the future.
Natural selection only acts on populations, not individual organisms. This is a significant distinction from the Lamarckian theory of evolution, which states that animals acquire characteristics through use or disuse. For example, if a giraffe's neck gets longer through stretching to reach prey its offspring will inherit a larger neck. The difference in neck length between generations will continue until the neck of the giraffe becomes so long that it can not breed with other giraffes.
Evolution through Genetic Drift
Genetic drift occurs when alleles from a gene are randomly distributed in a group. Eventually, only one will be fixed (become common enough that it can no longer be eliminated by natural selection), and the rest of the alleles will drop in frequency. In the extreme, this leads to dominance of a single allele. Other alleles have been basically eliminated and heterozygosity has been reduced to a minimum. In a small group it could lead to the total elimination of recessive allele. This scenario is known as a bottleneck effect and it is typical of evolutionary process that occurs when a large amount of people migrate to form a new population.
A phenotypic bottleneck can also occur when the survivors of a catastrophe such as an outbreak or mass hunt event are confined to a small area. The surviving individuals will be mostly homozygous for the dominant allele which means they will all have the same phenotype, and consequently have the same fitness characteristics. This can be caused by war, earthquakes, or even plagues. Regardless of the cause the genetically distinct population 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 instance of twins who are genetically identical, have the exact same phenotype and yet one is struck by lightning and dies, while the other lives and reproduces.
This type of drift can 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 phenotypic diversity within a population.
Stephens claims that there is a significant distinction between treating drift as a force, or an underlying cause, and treating other causes of evolution like mutation, selection, and migration as forces or causes. Stephens claims that a causal process account of drift allows us distinguish it from other forces and this differentiation is crucial. 에볼루션게이밍 argues that drift has a direction, that is it tends to eliminate heterozygosity, and that it also has a size, that is determined by the size of the population.
Evolution by Lamarckism
In high school, students take biology classes, they are frequently introduced to the work of Jean-Baptiste Lamarck (1744 - 1829). His theory of evolution, also referred to as "Lamarckism, states that simple organisms develop into more complex organisms inheriting characteristics that result from the use and abuse of an organism. Lamarckism is illustrated through a giraffe extending its neck to reach higher levels of leaves in the trees. This causes the longer necks of giraffes to be passed to their offspring, who would then become taller.
Lamarck, a French zoologist, presented an innovative idea in his 17 May 1802 opening lecture at the Museum of Natural History of Paris. 바카라 에볼루션 challenged traditional thinking about organic transformation. In his opinion, living things had evolved from inanimate matter via a series of gradual steps. Lamarck was not the only one to suggest that this could be the case, but he is widely seen as being the one who gave the subject its first general and thorough treatment.
The dominant story is that Charles Darwin's theory of evolution by natural selection and Lamarckism were rivals in the 19th Century. Darwinism eventually prevailed, leading to the development of what biologists today refer to as the Modern Synthesis. This theory denies acquired characteristics are passed down from generation to generation and instead argues that organisms evolve through the selective influence of environmental factors, such as Natural Selection.
While Lamarck believed in the concept of inheritance through acquired characters and his contemporaries spoke of this idea however, it was not an integral part of any of their evolutionary theories. This is partly because it was never tested 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 base that supports the heritability acquired characteristics. This is also known as "neo Lamarckism", or more generally epigenetic inheritance. This is a variant that is as reliable as the popular neodarwinian model.
Evolution through the process of adaptation
One of the most common misconceptions about evolution is that it is being driven by a struggle to survive. This view is a misrepresentation of natural selection and ignores the other forces that are driving evolution. The fight for survival can be more effectively described as a struggle to survive in a specific environment, which may involve not only other organisms but as well the physical environment.
Understanding adaptation is important to understand evolution. Adaptation is any feature that allows a living organism to survive in its environment and reproduce. It could be a physiological structure like feathers or fur or a behavioral characteristic like moving into shade in hot weather or coming out at night to avoid the cold.
The capacity of a living thing to extract energy from its surroundings and interact with other organisms and their physical environments, is crucial to its survival. The organism should possess the right genes to create offspring, and be able to find enough food and resources. In addition, the organism should be capable of reproducing itself in a way that is optimally within its niche.
These factors, together with mutation and gene flow can result in an alteration in the percentage of alleles (different varieties of a particular gene) 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 in the course of time.
Many of the features we appreciate in plants and animals are adaptations. For example lung or gills that extract oxygen from air, fur and feathers as insulation and long legs to get away from predators and camouflage for hiding. However, a complete understanding of adaptation requires paying attention to the distinction between behavioral and physiological traits.
Physiological traits like large gills and thick fur are physical traits. Behavior adaptations aren't like the tendency of animals to seek companionship or to retreat into the shade in hot temperatures. It is important to remember that a insufficient planning does not make an adaptation. In fact, a failure to think about the implications of a behavior can make it ineffective even though it appears to be logical or even necessary.