What is Free Evolution?
Free evolution is the idea that natural processes can cause organisms to develop over time. This includes the emergence and development of new species.
This has been demonstrated by many examples such as the stickleback fish species that can live in saltwater or fresh water and walking stick insect types that have a preference for particular host plants. These are mostly reversible traits, however, cannot explain fundamental changes in body plans.
Evolution through Natural Selection
The development of the myriad living organisms on Earth is a mystery that has fascinated scientists for centuries. Charles Darwin's natural selection theory is the most well-known explanation. This is because people who are more well-adapted have more success in reproduction and survival than those who are less well-adapted. Over time, the population of individuals who are well-adapted grows and eventually develops into a new species.
Natural selection is a process that is cyclical and involves the interaction of three factors including reproduction, variation and inheritance. Sexual reproduction and mutations increase genetic diversity in a species. Inheritance is the passing of a person's genetic characteristics to his or her offspring that includes dominant and recessive alleles. Reproduction is the generation of fertile, viable offspring, which includes both sexual and asexual methods.
Natural selection is only possible when all the factors are in equilibrium. If, for example an allele of a dominant gene causes an organism reproduce and last longer than the recessive gene allele The dominant allele becomes more prevalent in a group. However, if the gene confers an unfavorable survival advantage or reduces fertility, it will disappear from the population. This process is self-reinforcing meaning that an organism that has an adaptive characteristic will live and reproduce far more effectively than those with a maladaptive trait. The higher the level of fitness an organism has as measured by its capacity to reproduce and survive, is the greater number of offspring it will produce. People with desirable traits, like the long neck of the giraffe, or bright white color patterns on male peacocks, are more likely than others to live and reproduce and eventually lead to them becoming the majority.
Natural selection is an aspect of populations and not on individuals. This is a crucial distinction from the Lamarckian evolution theory, which states that animals acquire traits through use or lack of use. If a giraffe stretches its neck to reach prey and the neck grows longer, 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
Genetic drift occurs when alleles from a gene are randomly distributed in a group. In the end, only one will be fixed (become widespread enough to not longer be eliminated through natural selection) and the rest of the alleles will drop in frequency. In the extreme, this leads to a single allele dominance. The other alleles are essentially eliminated, and heterozygosity falls to zero. In a small population it could lead to the total elimination of recessive alleles. This scenario is called the bottleneck effect and is typical of an evolutionary process that occurs when the number of individuals migrate to form a population.
A phenotypic bottleneck could occur when survivors of a catastrophe, such as an epidemic or a massive hunting event, are condensed within a narrow area. The survivors will be mostly homozygous for the dominant allele, which means that they will all have the same phenotype and therefore have the same fitness characteristics. This may be caused by a war, earthquake or even a cholera outbreak. Whatever the reason, the genetically distinct population that remains is prone to genetic drift.
Walsh Lewens, Walsh and Ariew define drift as a deviation from expected values due to differences in fitness. 에볼루션 무료체험 cite a famous instance of twins who are genetically identical and have identical phenotypes, and yet one is struck by lightning and dies, while the other lives and reproduces.
This type of drift can play a significant role in the evolution of an organism. However, it's not the only way to progress. Natural selection is the primary alternative, where mutations and migration maintain the phenotypic diversity in a population.
Stephens asserts that there is a significant difference between treating drift as a force or a cause and treating other causes of evolution such as selection, mutation and migration as forces or causes. He argues that a causal mechanism account of drift allows us to distinguish it from other forces, and that this distinction is vital. He also argues that drift has a direction: that is it tends to eliminate heterozygosity, and that it also has a size, which is determined by the size of population.
Evolution by Lamarckism
In high school, students study biology they are often introduced to the work of Jean-Baptiste Lamarck (1744 - 1829). His theory of evolution, often called "Lamarckism is based on the idea that simple organisms evolve into more complex organisms by taking on traits that are a product of the organism's use and misuse. Lamarckism is usually illustrated with a picture of a giraffe stretching its neck to reach higher up in the trees. This causes the necks of giraffes that are longer to be passed onto their offspring who would then grow even 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 previous thinking on organic transformation. According to Lamarck, living things evolved from inanimate matter through a series gradual steps. Lamarck was not the first to make this claim however he was widely regarded as the first to give the subject a thorough and general explanation.
The predominant story is that Charles Darwin's theory of natural selection and Lamarckism were rivals in the 19th century. Darwinism eventually prevailed, leading to what biologists refer to as the Modern Synthesis. This theory denies that traits acquired through evolution can be acquired through inheritance and instead suggests that organisms evolve through the action of environmental factors, such as natural selection.
While Lamarck supported the notion of inheritance through acquired characters, and his contemporaries also paid lip-service to this notion, it was never an integral part of any of their theories about evolution. This is partly because it was never scientifically validated.
It's been more than 200 years since the birth of Lamarck and in the field of genomics, there is a growing body of evidence that supports the heritability-acquired characteristics. This is also known as "neo Lamarckism", or more generally epigenetic inheritance. It is a version of evolution that is just as valid as the more popular Neo-Darwinian theory.
Evolution by Adaptation
One of the most common misconceptions about evolution is that it is being driven by a struggle to survive. In fact, this view misrepresents natural selection and ignores the other forces that are driving evolution. The fight for survival is better described as a struggle to survive in a certain environment. This could be a challenge for not just other living things but also the physical environment.
To understand how evolution works, it is helpful to understand what is adaptation. The term "adaptation" refers to any characteristic that allows a living thing to survive in its environment and reproduce. It could be a physical structure, like feathers or fur. It could also be a behavior trait that allows you to move into the shade during hot weather, or moving out to avoid the cold at night.
The capacity of an organism to extract energy from its environment and interact with other organisms as well as their physical environments, is crucial to its survival. The organism must have the right genes to produce offspring and be able find enough food and resources. The organism must be able to reproduce itself at the rate that is suitable for its specific niche.
These factors, together with gene flow and mutations can cause an alteration in the ratio of different alleles in the population's gene pool. The change in frequency of alleles can lead to the emergence of novel traits and eventually, new species in the course of time.
Many of the features that we admire in animals and plants are adaptations, for example, lung or gills for removing oxygen from the air, feathers or fur for insulation long legs to run away from predators and camouflage for hiding. However, a complete understanding of adaptation requires paying attention to the distinction between physiological and behavioral characteristics.
Physiological adaptations, like thick fur or gills, are physical characteristics, whereas behavioral adaptations, like the desire to find companions or to move into the shade in hot weather, aren't. It is important to note that insufficient planning does not make an adaptation. In fact, failing to consider the consequences of a behavior can make it unadaptive even though it may appear to be logical or even necessary.