What is Free Evolution?
Free evolution is the notion that natural processes can cause organisms to develop over time. This includes the development of new species and change in appearance of existing ones.
This has been demonstrated by numerous examples such as the stickleback fish species that can live in fresh or saltwater and walking stick insect species that have a preference for 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 organisms on Earth is an enigma that has fascinated scientists for centuries. The best-established explanation is that of Charles Darwin's natural selection process, which occurs when individuals that are better adapted survive and reproduce more successfully than those less well-adapted. Over time, a population of well adapted individuals grows and eventually becomes 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 the genetic diversity of the species. Inheritance is the term used to describe the transmission of a person’s genetic characteristics, which includes recessive and dominant genes, to their offspring. Reproduction is the generation of fertile, viable offspring, which includes both asexual and sexual methods.
Natural selection is only possible when all the factors are in balance. If, for example, a dominant gene allele causes an organism reproduce and last longer than the recessive gene, then the dominant allele is more prevalent in a group. If the allele confers a negative survival advantage or decreases the fertility of the population, it will be eliminated. This process is self-reinforcing meaning that a species that has a beneficial trait will survive and reproduce more than an individual with a maladaptive characteristic. The more fit an organism is which is measured by its ability to reproduce and survive, is the more offspring it will produce. People with good characteristics, such as the long neck of giraffes, or bright white color patterns on male peacocks, are more likely than others to live and reproduce 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 neglect. If a giraffe expands its neck to reach prey, and the neck becomes longer, then the children will inherit this characteristic. The difference in neck size between generations will continue to grow until the giraffe is no longer able to reproduce with other giraffes.
Evolution through Genetic Drift
Genetic drift occurs when the alleles of one gene are distributed randomly in a group. At some point, one will reach fixation (become so common that it is unable to be eliminated through natural selection), while other alleles will fall to lower frequency. In the extreme this, it leads to one allele dominance. Other alleles have been basically eliminated and heterozygosity has diminished to a minimum. In Evolution KR could lead to the total elimination of recessive alleles. This scenario is called the bottleneck effect and is typical of the evolutionary process that occurs when the number of individuals migrate to form a group.
A phenotypic bottleneck could happen when the survivors of a catastrophe such as an epidemic or a massive hunting event, are concentrated within a narrow area. The remaining individuals are likely to be homozygous for the dominant allele which means they will all share the same phenotype, and consequently have the same fitness characteristics. This situation could be caused by earthquakes, war or even a plague. The genetically distinct population, if it is left susceptible to genetic drift.
Walsh Lewens, Walsh, and Ariew define drift as a departure from expected values due to differences in fitness. They cite the famous example of twins who are both genetically identical and share the same phenotype, but one is struck by lightning and dies, whereas the other continues to reproduce.
This type of drift is crucial in the evolution of an entire species. However, it is not the only method to progress. The primary alternative is a process known as natural selection, in which phenotypic variation in an individual is maintained through mutation and migration.
Stephens asserts that there is a significant difference between treating the phenomenon of drift as a force or a cause and considering other causes of evolution such as mutation, selection and migration as forces or causes. He argues that a causal mechanism account of drift allows us to distinguish it from these other forces, and this distinction is crucial. He also argues that drift has a direction: that is it tends to reduce heterozygosity, and that it also has a magnitude, that is determined by the size of the population.
Evolution by Lamarckism
Students of biology in high school are often exposed to Jean-Baptiste lamarck's (1744-1829) work. His theory of evolution, often referred to as "Lamarckism, states that simple organisms develop into more complex organisms taking on traits that are a product of the use and abuse of an organism. Lamarckism is illustrated through the giraffe's neck being extended to reach higher leaves in the trees. This would result in giraffes passing on their longer necks to their offspring, who then grow even taller.
Lamarck was a French zoologist and, in his inaugural lecture for his course on invertebrate zoology held at the Museum of Natural History in Paris on the 17th May 1802, he introduced a groundbreaking concept that radically challenged the previous understanding of organic transformation. According to him living things had evolved from inanimate matter through the gradual progression of events. Lamarck was not the only one to suggest that this might be the case but he is widely seen as having given the subject his first comprehensive and thorough treatment.
The prevailing 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 ultimately won which led to what biologists call the Modern Synthesis. This theory denies the possibility that acquired traits can be inherited and instead, it argues that organisms develop through the action of environmental factors, including natural selection.
Although Lamarck supported the notion of inheritance through acquired characters, and his contemporaries also spoke of this idea but it was not a major feature in any of their theories about evolution. This is largely due to the fact that it was never tested scientifically.
It's been more than 200 years since Lamarck was born and, in the age of genomics there is a vast amount of evidence to support the heritability of acquired characteristics. This is often referred to as "neo-Lamarckism" or more frequently epigenetic inheritance. This is a version that is as valid as the popular neodarwinian model.
Evolution through the process of adaptation
One of the most commonly-held misconceptions about evolution is its being driven by a fight for survival. This notion is not true and overlooks other forces that drive evolution. The fight for survival can be more accurately described as a struggle to survive in a specific environment, which can include not just other organisms but also the physical environment.
Understanding the concept of adaptation is crucial to comprehend evolution. The term "adaptation" refers to any characteristic that allows living organisms to live in its environment and reproduce. It could 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 extract energy from the environment and interact with other living organisms and their physical surroundings. The organism should possess the right genes to produce offspring and to be able to access sufficient food and resources. Furthermore, the organism needs to be capable of reproducing at a high rate within its environmental niche.
These elements, along with mutations and gene flow, can lead to a shift in the proportion of different alleles in the gene pool of a population. As time passes, this shift in allele frequencies could result in the emergence of new traits, and eventually 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 to provide insulation, long legs for running away from predators and camouflage for hiding. However, a proper understanding of adaptation requires paying attention to the distinction between behavioral and physiological characteristics.
Physiological adaptations like the thick fur or gills are physical traits, while behavioral adaptations, such as the desire to find companions or to move to shade in hot weather, aren't. It is also important to keep in mind that insufficient planning does not result in an adaptation. In fact, failure to consider the consequences of a behavior can make it unadaptive even though it appears to be logical or even necessary.