What is Free Evolution?
Free evolution is the notion that the natural processes of organisms can cause them to develop over time. This includes the emergence and development of new species.
A variety of examples have been provided of this, including different kinds of stickleback fish that can live in either fresh or salt water and walking stick insect varieties that prefer specific host plants. These mostly reversible trait permutations, however, cannot be the reason for fundamental changes in body plans.
Evolution through Natural Selection
Scientists have been fascinated by the evolution of all living organisms that inhabit our planet for many centuries. The most well-known explanation is that of Charles Darwin's natural selection, which occurs when individuals that are better adapted survive and reproduce more effectively than those less well adapted. Over time, a population of well-adapted individuals expands and eventually creates a new species.
Natural selection is a cyclical process that is characterized by the interaction of three elements: variation, inheritance and reproduction. Variation is caused by mutation and sexual reproduction both of which enhance the genetic diversity within the species. Inheritance is the passing of a person's genetic traits to the offspring of that person that includes recessive and dominant alleles. Reproduction is the generation of viable, fertile offspring, which includes both asexual and sexual methods.
Natural selection is only possible when all these elements are in balance. If, for example an allele of a dominant gene allows an organism to reproduce and survive more than the recessive allele, then the dominant allele becomes more prevalent in a group. If the allele confers a negative survival advantage or decreases the fertility of the population, it will disappear. The process is self-reinforcing, meaning that an organism that has a beneficial trait is more likely to survive and reproduce than an individual with an inadaptive trait. The more fit an organism is which is measured by its ability to reproduce and endure, is the higher number of offspring it can produce. People with desirable characteristics, like longer necks in giraffes and bright white color patterns in male peacocks are more likely survive and produce offspring, and thus will make up the majority of the population over time.
Natural selection is only a force for populations, not individual organisms. This is an important distinction from the Lamarckian theory of evolution, which argues that animals acquire characteristics by use or inactivity. If a giraffe expands its neck to catch prey and the neck grows longer, then the offspring will inherit this characteristic. The differences in neck length between generations will persist until the giraffe's neck becomes so long that it can not breed with other giraffes.
Evolution through Genetic Drift
Genetic drift occurs when alleles from the same gene are randomly distributed within a population. Eventually, only one will be fixed (become widespread enough to not more be eliminated through natural selection) and the other alleles drop in frequency. In the extreme this, it leads to a single allele dominance. The other alleles are essentially eliminated, and heterozygosity falls to zero. In a small number of people this could lead to the complete elimination of recessive gene. This scenario is known as a bottleneck effect and it is typical of the kind of evolutionary process that takes place when a large amount of individuals move to form a new group.
A phenotypic bottleneck may also occur when survivors of a disaster such as an outbreak or a mass hunting event are confined to the same area. The survivors will carry an dominant allele, and will have the same phenotype. This may be the result of a war, an earthquake or even a cholera outbreak. The genetically distinct population, if left susceptible to genetic drift.
Walsh, Lewens and Ariew define drift as a departure from expected values due to differences in fitness. They provide a well-known instance of twins who are genetically identical and have the exact same phenotype and yet one is struck by lightning and dies, while the other lives and reproduces.
This type of drift is vital to the evolution of the species. However, it is not the only way to progress. Natural selection is the main alternative, in which mutations and migration maintain phenotypic diversity within the population.
Stephens asserts that there is a significant distinction between treating drift as an actual cause or force, and considering other causes, such as selection mutation and migration as forces and causes. He claims that a causal-process explanation of drift lets us distinguish it from other forces and that this distinction is essential. He also argues that drift is both direction, i.e., it tends towards eliminating heterozygosity. It also has a size which is determined based on population size.
Evolution through Lamarckism
When students in high school take biology classes, they are frequently 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 adopting traits that result from the use and abuse of an organism. Lamarckism is illustrated through the giraffe's neck being extended to reach higher levels of leaves in the trees. This causes giraffes' longer necks to be passed on to their offspring who would grow taller.
Lamarck, a French Zoologist, introduced an idea that was revolutionary in his 17 May 1802 opening lecture at the Museum of Natural History of Paris. He challenged conventional wisdom on organic transformation. According to Lamarck, living things evolved from inanimate materials by a series of gradual steps. Lamarck wasn't the first to make this claim, but he was widely thought of as the first to provide the subject a thorough and general overview.
The most popular story is that Charles Darwin's theory of natural selection and Lamarckism fought in the 19th century. Darwinism ultimately won which led to what biologists refer to as the Modern Synthesis. The theory argues that acquired traits can be passed down and instead argues that organisms evolve through the selective action of environment factors, such as Natural Selection.
에볼루션 슬롯 and his contemporaries endorsed the idea that acquired characters could be passed on to future generations. However, this idea was never a major part of any of their theories on evolution. This is partly because it was never scientifically tested.
It's been over 200 year since Lamarck's birth, and in the age 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 well-known neo-Darwinian model.
Evolution by Adaptation
One of the most common misconceptions about evolution is that it is driven by a sort of struggle for survival. In fact, this view is inaccurate and overlooks the other forces that are driving evolution. The fight for survival can be more accurately described as a struggle to survive in a specific environment, which can involve not only other organisms, but also the physical environment itself.
Understanding adaptation is important to understand evolution. It is a feature that allows a living thing to survive in its environment and reproduce. It can be a physical structure such as feathers or fur. Or it can be a characteristic of behavior, like moving towards shade during the heat, or escaping the cold at night.
The capacity of an organism to draw energy from its environment and interact with other organisms as well as their physical environment is essential to its survival. The organism should possess the right genes to produce offspring and be able find sufficient food and resources. In addition, the organism should be able to reproduce itself at a high rate within its niche.
These factors, together with gene flow and mutations can result in an alteration in the ratio of different alleles within the population's gene pool. As time passes, this shift in allele frequencies could lead to the emergence of new traits and ultimately new species.
Many of the characteristics we admire about animals and plants are adaptations, like lungs or gills to extract oxygen from the air, fur or feathers to protect themselves long legs to run away from predators and camouflage to hide. However, a thorough understanding of adaptation requires a keen eye to the distinction between physiological and behavioral characteristics.
Physiological traits like large gills and thick fur are physical traits. Behavior adaptations aren't an exception, for instance, the tendency of animals to seek out companionship or move into the shade in hot temperatures. It is important to keep in mind that lack of planning does not result in an adaptation. In fact, failing to consider the consequences of a behavior can make it unadaptable even though it may appear to be logical or even necessary.