What is Free Evolution?
Free evolution is the notion that the natural processes that organisms go through can cause them to develop over time. This includes the appearance and growth of new species.
Numerous examples have been offered of this, including various varieties of fish called sticklebacks that can live in either fresh or salt water and walking stick insect varieties that are attracted to specific host plants. These mostly reversible trait permutations, however, cannot explain fundamental changes in basic body plans.
Evolution through Natural Selection
The development of the myriad of living creatures on Earth is a mystery that has intrigued scientists for centuries. The most widely accepted explanation is Charles Darwin's natural selection process, an evolutionary process that occurs when better-adapted individuals survive and reproduce more effectively than those less well-adapted. Over time, a community of well-adapted individuals increases and eventually creates a new species.
Natural selection is a cyclical process that is characterized by 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 of a species. Inheritance is the passing of a person's genetic characteristics to their offspring which includes both dominant and recessive alleles. Reproduction is the process of producing viable, fertile offspring. This can be done by both asexual or sexual methods.
Natural selection only occurs when all of these factors are in harmony. For instance the case where an allele that is dominant at one gene causes an organism to survive and reproduce more often than the recessive allele, the dominant allele will become more prominent in the population. However, if the allele confers an unfavorable survival advantage or decreases fertility, it will disappear from the population. The process is self reinforcing which means that an organism with an adaptive characteristic will live and reproduce far more effectively than those with a maladaptive feature. The higher the level of fitness an organism has which is measured by its ability to reproduce and survive, is the more offspring it produces. People with good traits, like having a long neck in the giraffe, or bright white patterns on male peacocks are more likely to others to reproduce and survive which eventually leads to them becoming the majority.
Natural selection only affects populations, not on individuals. This is a major distinction from the Lamarckian theory of evolution, which argues that animals acquire characteristics through use or disuse. If a giraffe extends its neck to reach prey and the neck grows longer, then the children will inherit this characteristic. The length difference between generations will persist until the giraffe's neck becomes too long that it can no longer breed with other giraffes.
Evolution through Genetic Drift
Genetic drift occurs when alleles of one gene are distributed randomly in a population. Eventually, one of them will attain fixation (become so common that it can no longer be eliminated by natural selection), while other alleles fall to lower frequency. This could lead to dominance in extreme. The other alleles are essentially eliminated, and heterozygosity is reduced to zero. In a small number of people this could result in the complete elimination of recessive alleles. Such a scenario would be known as a bottleneck effect and it is typical of the kind of evolutionary process that occurs when a large amount of individuals migrate to form a new population.
A phenotypic bottleneck can also occur when survivors of a disaster, such as an epidemic or a massive hunting event, are condensed within a narrow area. The survivors will be largely homozygous for the dominant allele which means that they will all have the same phenotype and will consequently share the same fitness characteristics. This can be caused by earthquakes, war or even plagues. Regardless of the cause, the genetically distinct population that remains could be susceptible to genetic drift.
Walsh Lewens, Walsh, and Ariew define drift as a deviation from the expected values due to differences in fitness. They cite the famous example of twins who are genetically identical and share the same phenotype. However, one is struck by lightning and dies, while the other lives to reproduce.
This kind of drift can play a very important role in the evolution of an organism. It is not the only method of evolution. The most common alternative is a process called natural selection, in which the phenotypic variation of an individual is maintained through mutation and migration.
Stephens asserts that there is a significant distinction between treating drift as a force or as a cause and considering other causes of evolution such as selection, mutation and migration as forces or causes. He claims that a causal process account of drift permits us to differentiate it from these other forces, and this distinction is essential. He also claims that drift has a direction, that is it tends to reduce heterozygosity. He also claims that it also has a magnitude, that is determined by population size.
Evolution through Lamarckism
When high school students study biology they are often introduced to the work of Jean-Baptiste Lamarck (1744 - 1829). His theory of evolution is commonly called "Lamarckism" and it states that simple organisms grow into more complex organisms via the inherited characteristics that result from an organism's natural activities, use and disuse. Lamarckism can be demonstrated by an giraffe's neck stretching to reach higher branches in the trees. This process would cause giraffes to give their longer necks to their offspring, who would then become taller.
Lamarck the French Zoologist from France, presented an innovative idea in his 17 May 1802 opening lecture at the Museum of Natural History of Paris. He challenged conventional wisdom on organic transformation. According to click the following article , living creatures evolved from inanimate materials through a series gradual steps. Lamarck was not the only one to suggest that this could be the case but his reputation is widely regarded as having given the subject its first broad and comprehensive treatment.
The most popular story is that Lamarckism was an opponent to Charles Darwin's theory of evolution through natural selection, and that the two theories battled it out in the 19th century. Darwinism eventually triumphed and led to the creation of what biologists now call the Modern Synthesis. This theory denies acquired characteristics can be passed down and instead argues that organisms evolve through the influence of environment factors, such as Natural Selection.
Lamarck and his contemporaries endorsed the notion that acquired characters could be passed down to the next generation. However, this idea was never a key element of any of their evolutionary theories. This is partly due to the fact that it was never validated scientifically.
It's been more than 200 years since the birth of Lamarck and in the field of genomics there is a growing evidence base that supports the heritability acquired characteristics. This is often referred to as "neo-Lamarckism" or more frequently epigenetic inheritance. This is a variant that is as valid as the popular neodarwinian model.
Evolution through adaptation
One of the most popular misconceptions about evolution is its being driven by a struggle for survival. In fact, this view misrepresents natural selection and ignores the other forces that determine the rate of evolution. The struggle for survival is more accurately described as a struggle to survive within a specific environment, which could include not just other organisms but also the physical environment.
Understanding adaptation is important to understand evolution. Adaptation refers to any particular feature that allows an organism to survive and reproduce in its environment. It can be a physical structure, like fur or feathers. Or it can be a trait of behavior, like moving towards shade during hot weather, or escaping the cold at night.
An organism's survival depends on its ability to obtain energy from the environment and to interact with other organisms and their physical environments. The organism needs to have the right genes to create offspring, and must be able to locate enough food and other resources. Furthermore, the organism needs to be capable of reproducing itself in a way that is optimally within its environmental niche.
These factors, along with mutation and gene flow can result in an alteration in the percentage of alleles (different types of a gene) in a population's gene pool. Over time, this change in allele frequencies could lead to the emergence of new traits and eventually new species.
Many of the characteristics we find appealing in plants and animals are adaptations. For example the lungs or gills which extract oxygen from the air feathers and fur for insulation and long legs to get away from predators and camouflage for hiding. To understand adaptation it is crucial to differentiate between physiological and behavioral characteristics.
Physiological adaptations, like the thick fur or gills are physical traits, while behavioral adaptations, like the tendency to search for friends or to move to the shade during hot weather, are not. Furthermore it is important to remember that a lack of forethought does not mean that something is an adaptation. In fact, a failure to think about the consequences of a behavior can make it ineffective, despite the fact that it might appear sensible or even necessary.