What is Free Evolution?
Free evolution is the concept that the natural processes of organisms can lead to their development over time. This includes the appearance and development of new species.
This has been demonstrated by many examples of stickleback fish species that can be found in saltwater or fresh water and walking stick insect species that have a preference for specific host plants. These are mostly reversible traits can't, however, explain fundamental changes in body plans.
Evolution through Natural Selection
Scientists have been fascinated by the evolution of all living creatures that inhabit our planet for centuries. Charles Darwin's natural selection theory is the most well-known explanation. This process occurs when people who are more well-adapted survive and reproduce more than those who are less well-adapted. Over time, the population of well-adapted individuals grows and eventually forms an entirely new species.
Natural selection is an ongoing process and involves the interaction of three factors including reproduction, variation and inheritance. Mutation and sexual reproduction increase the genetic diversity of an animal species. Inheritance refers to the passing of a person's genetic characteristics to their offspring, which includes both dominant and recessive alleles. Reproduction is the process of producing fertile, viable offspring. This can be achieved via sexual or asexual methods.
Natural selection only occurs when all of these factors are in equilibrium. If, for instance the dominant gene allele makes an organism reproduce and last longer than the recessive allele, then the dominant allele is more prevalent in a population. If the allele confers a negative advantage to survival or reduces the fertility of the population, it will disappear. The process is self reinforcing which means that the organism with an adaptive trait will survive and reproduce far more effectively than one with a maladaptive characteristic. The more fit an organism is as measured by its capacity to reproduce and survive, is the more offspring it produces. People with good traits, such as a longer neck in giraffes, or bright white colors in male peacocks are more likely be able to survive and create offspring, so they will become the majority of the population over time.
Natural selection only acts on populations, not on individuals. This is a crucial distinction from the Lamarckian evolution kr theory which holds that animals acquire traits either through use or lack of use. For instance, if the giraffe's neck gets longer through stretching to reach for prey its offspring will inherit a more long neck. The difference in neck length between generations will persist until the giraffe's neck gets too long to no longer breed with other giraffes.
Evolution by Genetic Drift
In genetic drift, the alleles within a gene can attain different frequencies in a group through random events. At some point, only one of them will be fixed (become widespread enough to not longer be eliminated through natural selection), and the rest of the alleles will diminish in frequency. This can result in dominance in extreme. The other alleles are essentially eliminated, and heterozygosity falls to zero. In a small population, this could lead to the complete elimination of the recessive allele. This is known as the bottleneck effect and is typical of an evolutionary process that occurs when an enormous number of individuals move to form a group.
A phenotypic bottleneck could occur when survivors of a disaster, such as an epidemic or a massive hunt, are confined in a limited area. The remaining individuals are likely to be homozygous for the dominant allele which means that they will all share the same phenotype, and consequently have the same fitness traits. This situation might be caused by a conflict, earthquake or even a cholera outbreak. Regardless of the cause, the genetically distinct population that remains is prone to genetic drift.
Walsh, Lewens and Ariew define drift as a departure from the expected values due to differences in fitness. They give the famous example of twins that are genetically identical and have exactly the same phenotype. However, one is struck by lightning and dies, while the other continues to reproduce.
This kind of drift can play a significant role in the evolution of an organism. However, it is not the only method to progress. The main 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 big difference between treating the phenomenon of drift as a force or a cause and treating other causes of evolution like selection, mutation and migration as forces or causes. He argues that a causal process explanation of drift allows us to distinguish it from other forces, and that this distinction is vital. He also claims that drift has a direction: that is it tends to reduce heterozygosity, and that it also has a magnitude, which is determined by the size of population.
Evolution through 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 is commonly referred to as "Lamarckism" and it states that simple organisms grow into more complex organisms by the inheritance of traits that are a result of the natural activities of an organism, use and disuse. Lamarckism is usually illustrated with an image of a giraffe that extends its neck further to reach leaves higher up in the trees. This could result in giraffes passing on their longer necks to offspring, which then grow even taller.
Lamarck, a French zoologist, presented an innovative idea in his 17 May 1802 opening lecture at the Museum of Natural History of Paris. He challenged the previous thinking on organic transformation. According Lamarck, living organisms evolved from inanimate matter through a series of gradual steps. Lamarck wasn't the first to suggest this however he was widely regarded as the first to give the subject a comprehensive and general explanation.
The predominant story is that Charles Darwin's theory of evolution by natural selection and Lamarckism were competing in the 19th century. Darwinism ultimately won which led to what biologists call the Modern Synthesis. The theory denies that acquired characteristics can be passed down and instead argues that organisms evolve through the influence of environment factors, including Natural Selection.
Although Lamarck supported the notion of inheritance by acquired characters and his contemporaries also paid lip-service to this notion, it was never a major feature in any of their evolutionary theorizing. This is due in part to the fact that 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 an increasing evidence base that supports the heritability-acquired characteristics. This is also referred to as "neo Lamarckism", or more generally epigenetic inheritance. It is a form of evolution that is as relevant as the more popular Neo-Darwinian model.
Evolution through the process of adaptation
One of the most common misconceptions about evolution is that it is driven by a type of struggle for survival. This is a false assumption and ignores other forces driving evolution. The struggle for existence is more accurately described as a struggle to survive in a particular environment. This could include not only other organisms but also the physical environment.
To understand how evolution functions it is beneficial to understand what is adaptation. It refers to a specific characteristic that allows an organism to survive and reproduce in its environment. It can be a physiological structure, such as feathers or fur, or a behavioral trait, such as moving to the shade during hot weather or stepping out at night to avoid the cold.
An organism's survival depends on its ability to obtain energy from the environment and interact with other living organisms and their physical surroundings. The organism must possess the right genes to create offspring, and it should be able to locate sufficient food and other resources. Furthermore, the organism needs to be able to reproduce itself at a high rate within its environment.
These elements, along with mutations and gene flow can result in an alteration in the ratio of different alleles in a population’s gene pool. As time passes, this shift in allele frequencies could result in the development of new traits and eventually new species.
Many of the characteristics we admire in animals and plants are adaptations, for example, the lungs or gills that extract oxygen from the air, fur or feathers for insulation long legs to run away from predators, and camouflage for hiding. However, a proper understanding of adaptation requires attention to the distinction between physiological and behavioral traits.
Physiological adaptations, like thick fur or gills are physical traits, while behavioral adaptations, such as the tendency to search for companions or to retreat 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, failing to think about the implications of a decision can render it ineffective even though it appears to be reasonable or even essential.