What is Free Evolution?
Free evolution is the concept that natural processes can cause organisms to evolve over time. This includes the emergence and development of new species.
This has been demonstrated by many examples, including stickleback fish varieties that can live in salt or fresh water, and walking stick insect varieties that prefer specific host plants. These reversible traits, however, cannot be the reason for fundamental changes in body plans.
Evolution by Natural Selection
The development of the myriad of living creatures on Earth is a mystery that has intrigued scientists for decades. Charles Darwin's natural selection is the best-established explanation. This happens when individuals who are better-adapted are able to reproduce faster and longer 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 an ongoing process that is characterized by the interaction of three factors: variation, inheritance and reproduction. Mutation and sexual reproduction increase genetic diversity in a species. Inheritance refers to the transmission of a person’s genetic traits, which include both dominant and recessive genes, to their offspring. Reproduction is the process of creating fertile, viable offspring. This can be achieved by both asexual or sexual methods.
Natural selection is only possible when all these elements are in harmony. If, for example an allele of a dominant gene causes an organism reproduce and live longer than the recessive allele, then the dominant allele is more prevalent in a population. However, if the gene confers a disadvantage in survival or decreases fertility, it will disappear from the population. This process is self-reinforcing, which means that an organism that has an adaptive trait will live and reproduce far more effectively than those with a maladaptive trait. The more offspring that an organism has the more fit it is that is determined by its ability to reproduce and survive. People with good traits, such as a longer neck in giraffes, or bright white patterns of color in male peacocks, are more likely to survive and have offspring, so they will make up the majority of the population in the future.
Natural selection is only a force for populations, not individuals. This is a crucial distinction from the Lamarckian theory of evolution, which states that animals acquire traits either through use or lack of use. For instance, if the Giraffe's neck grows longer due to stretching to reach prey its offspring will inherit a larger neck. 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 by Genetic Drift
Genetic drift occurs when alleles from one gene are distributed randomly within a population. In the end, only one will be fixed (become common enough that it can no more be eliminated through natural selection) and the rest of the alleles will decrease in frequency. This can result in an allele that is dominant in the extreme. The other alleles have been essentially eliminated and heterozygosity has diminished to zero. In a small population, this could lead to the total elimination of recessive alleles. This scenario is called the bottleneck effect. It is typical of an evolution process that occurs when a large number individuals migrate to form a population.
A phenotypic bottleneck may occur when survivors of a disaster like an epidemic or a mass hunt, are confined within a narrow area. The surviving individuals are likely to be homozygous for the dominant allele, which means that they will all share the same phenotype and will therefore share the same fitness characteristics. This may be caused by conflict, earthquake or even a disease. The genetically distinct population, if left vulnerable to genetic drift.
Walsh Lewens, Lewens, and Ariew employ a "purely outcome-oriented" definition of drift as any deviation from the expected values for differences in fitness. They cite the famous example of twins who are genetically identical and have exactly the same phenotype. However one is struck by lightning and dies, while the other continues to reproduce.
This type of drift can play a significant role in the evolution of an organism. It is not the only method of evolution. The primary alternative is a process called natural selection, where phenotypic variation in the population is maintained through mutation and migration.
Stephens argues there is a huge difference between treating drift like an actual cause or force, and treating other causes such as migration and selection mutation as causes and forces. Stephens claims that a causal process account of drift allows us differentiate it from other forces, and this distinction is essential. He argues further that drift is both direction, i.e., it tends to eliminate heterozygosity. It also has a size that is determined by the size of the population.
Evolution through Lamarckism
Students of biology in high school are frequently introduced to Jean-Baptiste Lamarck's (1744-1829) work. His theory of evolution is commonly called "Lamarckism" and it asserts that simple organisms evolve into more complex organisms via the inheritance of characteristics which result from an organism's natural activities, use and disuse. Lamarckism is illustrated through an giraffe's neck stretching to reach higher branches in the trees. This would cause giraffes to pass on their longer necks to offspring, who then become taller.
Lamarck was a French zoologist and, in his opening lecture for his course on invertebrate zoology at the Museum of Natural History in Paris on 17 May 1802, he introduced an innovative concept that completely challenged previous thinking about organic transformation. According to Lamarck, living creatures evolved from inanimate material through a series gradual steps. Lamarck was not the only one to suggest that this might be the case, but the general consensus is that he was the one having given the subject its first broad and comprehensive treatment.
The most popular story is that Lamarckism grew into an opponent to Charles Darwin's theory of evolution by natural selection and that the two theories fought out in the 19th century. Darwinism eventually won and led to the creation of what biologists now refer to as the Modern Synthesis. The theory argues that traits acquired through evolution can be acquired through inheritance and instead argues that organisms evolve through the selective action of environmental factors, like natural selection.
This Internet page and his contemporaries endorsed the notion that acquired characters could be passed on to future generations. However, this notion was never a major part of any of their theories on evolution. This is partly due to the fact that it was never validated scientifically.
It has been more than 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 referred to as "neo Lamarckism", or more commonly epigenetic inheritance. This is a variant that is as reliable as the popular neodarwinian model.
Evolution through adaptation
One of the most popular misconceptions about evolution is being driven by a fight for survival. This is a false assumption and overlooks other forces that drive evolution. The struggle for existence is more accurately described as a struggle to survive in a certain environment. This can include not just other organisms, but also the physical surroundings themselves.
To understand how evolution operates it is important to consider what adaptation is. It is a feature that allows a living thing to survive in its environment and reproduce. It can be a physiological structure like feathers or fur, or a behavioral trait such as a tendency to move into the shade in the heat or leaving at night to avoid the cold.
The ability of a living thing 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 it should be able to access enough food and other resources. The organism should be able to reproduce at a rate that is optimal for its particular niche.
These factors, along with gene flow and mutation, lead to 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 result in the development of new traits and ultimately new species.
A lot of the traits we admire in animals and plants are adaptations, such as lung or gills for removing oxygen from the air, feathers or fur for insulation and long legs for running away from predators, and camouflage to hide. However, a complete understanding of adaptation requires paying attention to the distinction between physiological and behavioral characteristics.
Physiological adaptations, such as thick fur or gills, are physical traits, whereas 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 lack of planning does not make something an adaptation. Inability to think about the consequences of a decision, even if it appears to be rational, may make it inflexible.