What is Free Evolution?
Free evolution is the idea that the natural processes that organisms go through can lead them to evolve over time. This includes the evolution of new species and change in appearance of existing ones.
A variety of examples have been provided of this, including different varieties of fish called sticklebacks that can live in salt or fresh water, as well as walking stick insect varieties that favor specific 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 creatures on Earth is a mystery that has fascinated scientists for many centuries. Charles Darwin's natural selectivity is the most well-known explanation. This is because people who are more well-adapted are able to reproduce faster and longer than those who are less well-adapted. As time passes, a group of well-adapted individuals expands and eventually creates a new species.
Natural selection is an ongoing process and involves the interaction of 3 factors including reproduction, variation and inheritance. Sexual reproduction and mutations increase genetic diversity in an animal species. Inheritance refers to the passing of a person's genetic traits to the offspring of that person that includes recessive and dominant alleles. Reproduction is the production of fertile, viable offspring which includes both sexual and asexual methods.
All of these factors have to be in equilibrium for natural selection to occur. For example when the dominant allele of the gene causes an organism to survive and reproduce more frequently than the recessive allele the dominant allele will become more common within the population. However, if the gene confers an unfavorable survival advantage or reduces fertility, it will disappear from the population. This process is self-reinforcing which means that an organism with a beneficial trait is more likely to survive and reproduce than one with a maladaptive characteristic. The greater an organism's fitness which is measured by its ability to reproduce and endure, is the higher number of offspring it can produce. Individuals with favorable traits, such as longer necks in giraffes, or bright white color patterns in male peacocks are more likely survive and have offspring, and thus will become the majority of the population over time.
Natural selection only affects populations, not individuals. This is a significant distinction from the Lamarckian theory of evolution, which states that animals acquire characteristics by use or inactivity. If a giraffe expands its neck to catch prey, and the neck becomes longer, then the offspring will inherit this characteristic. The difference in neck length between generations will persist until the neck of the giraffe becomes too long to no longer breed with other giraffes.
Evolution by Genetic Drift
Genetic drift occurs when alleles from the same gene are randomly distributed within a population. In the end, only one will be fixed (become widespread enough to not longer be eliminated through natural selection) and the other alleles will decrease in frequency. In extreme cases, this leads to one allele dominance. The other alleles are basically eliminated and heterozygosity has been reduced to a minimum. In a small group, this could lead to the total elimination of recessive alleles. This scenario is called a bottleneck effect, and it is typical of evolutionary process when a large amount of individuals migrate to form a new group.
A phenotypic bottleneck may occur when survivors of a catastrophe such as an epidemic or a massive hunting event, are concentrated in a limited area. The surviving individuals are likely to be homozygous for the dominant allele, meaning that they all share the same phenotype and thus share the same fitness characteristics. This situation might be the result of a war, earthquake or even a disease. The genetically distinct population, if it remains, could be susceptible to genetic drift.
Walsh, Lewens and Ariew define drift as a deviation from the expected values due to differences in fitness. They give the famous example of twins who are both genetically identical and share the same phenotype. However one is struck by lightning and dies, but the other continues to reproduce.
This kind of drift could be very important in the evolution of a species. But, it's not the only method to develop. Natural selection is the primary alternative, in which mutations and migrations maintain phenotypic diversity within the population.
Stephens argues that there is a big distinction between treating drift as a force or a cause and treating other causes of evolution, such as selection, mutation and migration as causes or causes. He claims that a causal mechanism account of drift allows us to distinguish it from the other forces, and this distinction is crucial. He further argues that drift has a direction: that is it tends to reduce heterozygosity. He also claims that it also has a size, that is determined by the size of the population.
Evolution through Lamarckism
In high school, students study biology, they are often introduced to the work of Jean-Baptiste Lamarck (1744 - 1829). His theory of evolution, commonly referred to as "Lamarckism, states that simple organisms develop into more complex organisms by adopting traits that are a product of the organism's use and misuse. Lamarckism is illustrated through an giraffe's neck stretching to reach higher leaves in the trees. This could cause giraffes' longer necks to be passed onto their offspring who would grow taller.
Lamarck, a French zoologist, presented an idea that was revolutionary in his opening lecture at the Museum of Natural History of Paris. He challenged the conventional wisdom on organic transformation. According to Lamarck, living things evolved from inanimate material by a series of gradual steps. Lamarck was not the first to suggest this, but he was widely thought of as the first to provide the subject a comprehensive and general overview.
The most popular story is that Lamarckism was an opponent to Charles Darwin's theory of evolutionary natural selection and both theories battled it out in the 19th century. Darwinism eventually won and led to the creation of what biologists refer to as the Modern Synthesis. The theory denies that acquired characteristics can be passed down through generations and instead argues that organisms evolve through the selective action of environment factors, such as Natural Selection.
Although Going In this article endorsed the idea of inheritance through acquired characters, and his contemporaries also offered a few words about this idea but it was not an integral part of any of their theories about evolution. This is due to the fact that it was never tested scientifically.
It's been over 200 year since Lamarck's birth, and in the age genomics, there is a growing evidence-based body of evidence to support the heritability acquired characteristics. This is often called "neo-Lamarckism" or more frequently, epigenetic inheritance. This is a variant that is just as valid as the popular neodarwinian model.
Evolution through the process of adaptation
One of the most widespread misconceptions about evolution is that it is driven by a sort of struggle for survival. In reality, this notion is inaccurate and overlooks the other forces that drive evolution. The struggle for survival is more accurately described as a struggle to survive in a specific environment, which could be a struggle that involves not only other organisms but also the physical environment.
To understand how evolution works it is important to think about what adaptation is. The term "adaptation" refers to any specific characteristic that allows an organism to live and reproduce in its environment. It can be a physiological structure such as fur or feathers or a behavior such as a tendency to move into the shade in hot weather or stepping out at night to avoid the cold.
The survival of an organism is dependent on its ability to draw energy from the surrounding environment and interact with other organisms and their physical environments. The organism needs to have the right genes to produce offspring, and it should be able to locate sufficient food and other resources. In addition, the organism should be able to reproduce itself in a way that is optimally within its environmental niche.
These factors, together with gene flow and mutation can result in a change in the proportion of alleles (different types of a gene) in a population's gene pool. Over time, this change in allele frequencies can lead to the emergence of new traits, and eventually new species.
Many of the characteristics we admire about animals and plants are adaptations, such as the lungs or gills that extract oxygen from the air, fur or feathers to provide insulation, long legs for running away from predators, and camouflage for hiding. However, a complete understanding of adaptation requires attention to the distinction between physiological and behavioral traits.
Physiological adaptations, like thick fur or gills are physical characteristics, whereas behavioral adaptations, such as the desire to find companions or to retreat into the shade in hot weather, are not. Furthermore it is important to remember that lack of planning does not make something an adaptation. A failure to consider the consequences of a decision even if it appears to be rational, may cause it to be unadaptive.