What is Free Evolution?
Free evolution is the notion that the natural processes of living organisms can lead them to evolve over time. This includes the evolution of new species and alteration of the appearance of existing species.
This has been proven by many examples, including stickleback fish varieties that can be found in saltwater or fresh water and walking stick insect species that have a preference for specific host plants. These mostly reversible trait permutations however, are not able to explain fundamental changes in basic body plans.
Evolution by Natural Selection
The development of the myriad of living organisms on Earth is an enigma that has fascinated scientists for many centuries. The best-established explanation is Charles Darwin's natural selection, which is triggered when more well-adapted individuals live longer and reproduce more effectively than those that are less well adapted. Over time, a community of well-adapted individuals expands and eventually forms a whole new species.
Natural selection is an ongoing 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 enhance the genetic diversity within an animal species. Inheritance is the passing of a person's genetic traits to his or her offspring, which includes both dominant and recessive alleles. Reproduction is the process of producing viable, fertile offspring. This can be accomplished through sexual or asexual methods.
All of these variables must be in balance to allow natural selection to take place. For example when the dominant allele of one gene can cause an organism to live and reproduce more frequently than the recessive one, the dominant allele will be more prevalent in the population. If the allele confers a negative survival advantage or decreases the fertility of the population, it will disappear. The process is self reinforcing meaning that an organism with an adaptive trait will live and reproduce far more effectively than those with a maladaptive trait. The more offspring an organism can produce, the greater its fitness that is determined by its ability to reproduce itself and live. Individuals with favorable characteristics, like a longer neck in giraffes or bright white colors in male peacocks, are more likely to survive and have offspring, so they will become the majority of the population in the future.
Natural selection is an aspect of populations and not on individuals. This is a major distinction from the Lamarckian evolution theory, which states that animals acquire traits due to the use or absence of use. For instance, if a giraffe's neck gets longer through stretching to reach for prey, its offspring will inherit a larger neck. The differences in neck size between generations will increase until the giraffe is no longer able to reproduce with other giraffes.
Evolution by Genetic Drift
In genetic drift, alleles at a gene may attain different frequencies in a group through random events. At some point, one will attain fixation (become so widespread that it can no longer be removed through natural selection), while other alleles fall to lower frequencies. In the extreme it can lead to one allele dominance. The other alleles are eliminated, and heterozygosity falls to zero. In a small group this could result in the total elimination of recessive allele. Such a scenario would be called a bottleneck effect, and it is typical of the kind of evolutionary process that takes place when a large amount of individuals move to form a new group.
A phenotypic bottleneck could occur when the 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 share the same phenotype and thus have the same fitness traits. This could be caused by earthquakes, war or even a plague. The genetically distinct population, if left vulnerable to genetic drift.
Walsh Lewens, Walsh and Ariew define drift as a departure 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, but the other lives to reproduce.
This kind of drift could be very important in the evolution of an entire species. It is not the only method for evolution. Natural selection is the primary alternative, where mutations and migration keep phenotypic diversity within the population.
Stephens claims that there is a significant difference between treating drift like an agent or cause and considering other causes, such as selection mutation and migration as forces and causes. He argues that a causal-process model of drift allows us to separate it from other forces and that this distinction is essential. He also argues that drift has a direction, i.e., it tends to reduce 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 often introduced to Jean-Baptiste Lamarck's (1744-1829) work. His theory of evolution is commonly referred to as "Lamarckism" and it asserts that simple organisms evolve into more complex organisms through the inherited characteristics which result from the natural activities of an organism usage, use and disuse. Lamarckism can be illustrated by an giraffe's neck stretching to reach higher leaves in the trees. This could cause the longer necks of giraffes to be passed on to their offspring who would then become taller.
you can try this out was a French zoologist and, in his inaugural lecture for his course on invertebrate zoology at the Museum of Natural History in Paris on the 17th of May in 1802, he introduced an innovative concept that completely challenged the previous understanding of organic transformation. According to Lamarck, living creatures evolved from inanimate material by a series of gradual steps. Lamarck wasn't the first to suggest this but he was considered to be the first to offer the subject a thorough and general overview.
The most popular story is that Lamarckism became a rival to Charles Darwin's theory of evolution through natural selection and that the two theories fought it out in the 19th century. Darwinism ultimately won, leading to what biologists refer to as the Modern Synthesis. The theory denies that acquired characteristics can be passed down and instead argues organisms evolve by the influence of environment factors, such as Natural Selection.
Although Lamarck supported the notion of inheritance through acquired characters and his contemporaries offered a few words about this idea, it was never a major feature in any of their theories about evolution. This is due to the fact that it was never scientifically validated.
It has been more than 200 year since Lamarck's birth and in the field of genomics, there is a growing body of evidence that supports the heritability-acquired characteristics. This is referred to as "neo Lamarckism", or more commonly epigenetic inheritance. It is a version of evolution that is just as relevant as the more popular Neo-Darwinian model.
Evolution through Adaptation
One of the most commonly-held misconceptions about evolution is being driven by a struggle for survival. This view is inaccurate and overlooks other forces that drive evolution. The fight for survival can be more precisely described as a fight to survive in a specific environment, which could be a struggle that involves not only other organisms but also the physical environment.
Understanding the concept of adaptation is crucial to understand evolution. Adaptation refers to any particular feature that allows an organism to survive and reproduce within its environment. It can be a physical feature, like fur or feathers. Or it can be a characteristic of behavior, like moving into the shade during the heat, or moving out to avoid the cold at night.
The survival of an organism depends on its ability to draw energy from the environment and interact with other living organisms and their physical surroundings. The organism must have the right genes to create offspring, and must be able to find enough food and other resources. In addition, the organism should be capable of reproducing at an optimal rate within its environmental niche.
These factors, together with mutation and gene flow can result in a change in the proportion of alleles (different types of a gene) in the gene pool of a population. The change in frequency of alleles can result in the emergence of new traits and eventually, new species as time passes.
A lot of the traits we admire in animals and plants are adaptations. For instance, lungs or gills that extract oxygen from the air, fur and feathers as 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 characteristics.
Physical characteristics like thick fur and gills are physical characteristics. The behavioral adaptations aren't, such as the tendency of animals to seek out companionship or retreat into shade during hot temperatures. Additionally it is important to remember that a lack of forethought is not a reason to make something an adaptation. Failure to consider the consequences of a decision even if it appears to be rational, could make it inflexible.