What is Free Evolution?
Free evolution is the concept that the natural processes of living organisms can lead to their development over time. This includes the evolution of new species and change in appearance of existing species.
Many examples have been given of this, including different varieties of stickleback fish that can be found in salt or fresh water, as well as walking stick insect varieties that favor particular host plants. These reversible traits do not explain the fundamental changes in the body's basic plans.
Evolution by Natural Selection
Scientists have been fascinated by the development of all the living creatures that live on our planet for centuries. Charles Darwin's natural selection is the best-established explanation. This process occurs when individuals who are better-adapted have more success in reproduction and survival than those who are less well-adapted. Over time, the population of well-adapted individuals becomes larger and eventually develops into an entirely new species.
Natural selection is a cyclical process that is characterized by the interaction of three elements including inheritance, variation, and reproduction. Sexual reproduction and mutations increase the genetic diversity of an animal species. Inheritance is the transfer of a person's genetic characteristics to their offspring which includes both recessive and dominant alleles. Reproduction is the process of generating viable, fertile offspring. This can be accomplished via sexual or asexual methods.
Natural selection can only occur when all the factors are in harmony. For instance the case where an allele that is dominant at one gene can cause an organism to live and reproduce more frequently than the recessive one, the dominant allele will be more prominent in the population. However, if the allele confers a disadvantage in survival or decreases fertility, it will disappear from the population. The process is self-reinforcing which means that an organism with an adaptive characteristic will live and reproduce much more than those with a maladaptive feature. The greater an organism's fitness which is measured by its ability to reproduce and survive, is the greater number of offspring it can produce. People with desirable characteristics, such as a long neck in the giraffe, or bright white patterns on male peacocks are more likely to others to survive and reproduce which eventually leads to them becoming the majority.
Natural selection is only a force for populations, not on individuals. This is a major distinction from the Lamarckian theory of evolution which states that animals acquire characteristics by use or inactivity. If a giraffe expands its neck to reach prey, and the neck becomes longer, then its offspring will inherit this trait. The differences in neck length between generations will persist until the neck of the giraffe becomes too long that it can 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. Eventually, only one will be fixed (become common enough to no longer be eliminated through natural selection), and the rest of the alleles will decrease in frequency. In extreme cases it can lead to a single allele dominance. The other alleles are eliminated, and heterozygosity is reduced to zero. In a small number of people it could lead to the total elimination of recessive alleles. This scenario is called the bottleneck effect. It is typical of the evolutionary process that occurs when a large number individuals migrate to form a group.
A phenotypic bottleneck can also occur when the survivors of a disaster like an outbreak or mass hunt event are concentrated in a small area. The survivors will carry a dominant allele and thus will share the same phenotype. This could be caused by earthquakes, war or even a plague. Whatever the reason the genetically distinct group that remains could be susceptible to genetic drift.
Walsh Lewens and Ariew utilize a "purely outcome-oriented" definition of drift as any deviation from the expected values of variations in fitness. They cite the famous example of twins that are genetically identical and have exactly the same phenotype. However one is struck by lightning and dies, whereas the other is able to reproduce.
This type of drift is very important in the evolution of the species. This isn't the only method of evolution. Natural selection is the main alternative, where mutations and migrations maintain phenotypic diversity within a population.
Stephens claims that there is a vast difference between treating drift like an agent or cause and treating other causes such as migration and selection as causes and forces. He argues that a causal-process explanation of drift lets us separate it from other forces and this differentiation is crucial. He argues further that drift has both an orientation, i.e., it tends towards eliminating heterozygosity. It also has a size, which is determined by the size of the population.
Evolution by Lamarckism
Students of biology in high school are frequently exposed to Jean-Baptiste lamarck's (1744-1829) work. His theory of evolution, commonly referred to as "Lamarckism, states that simple organisms transform into more complex organisms by taking on traits that are a product of the use and abuse of an organism. Lamarckism can be demonstrated by the giraffe's neck being extended to reach higher branches in the trees. This process would result in giraffes passing on their longer necks to offspring, which then get 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 the 17th of May in 1802, he presented an innovative concept that completely challenged previous thinking about organic transformation. In his view, living things had evolved from inanimate matter through the gradual progression of events. Lamarck was not the only one to suggest that this could be the case but his reputation is widely regarded as giving the subject its first general 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 battled out in the 19th century. Darwinism eventually prevailed and led to the creation of what biologists call the Modern Synthesis. The theory argues that acquired characteristics can be inherited, and instead suggests that organisms evolve by the symbiosis of environmental factors, such as natural selection.
Lamarck and his contemporaries believed in the idea that acquired characters could be passed down to future generations. However, this idea was never a key element of any of their evolutionary theories. This is partly because it was never scientifically validated.
It's been more than 200 year since Lamarck's birth and in the field of genomics, there is an increasing body of evidence that supports the heritability-acquired characteristics. This is referred to as "neo Lamarckism", or more often epigenetic inheritance. This is a version that is as valid as the popular Neodarwinian model.
Evolution by the process of adaptation
One of the most widespread misconceptions about evolution is that it is a result of a kind of struggle to survive. In fact, this view misrepresents natural selection and ignores the other forces that determine the rate of evolution. see this for survival is more effectively described as a struggle to survive within a specific environment, which could include not just other organisms but also the physical environment.
Understanding adaptation is important to understand evolution. The term "adaptation" refers to any specific characteristic that allows an organism to live and reproduce in its environment. It can be a physical structure, like feathers or fur. Or it can be a behavior trait such as moving into the shade during hot weather or escaping the cold at night.
The ability of a living thing to extract energy from its surroundings and interact with other organisms as well as their physical environments is essential to its survival. The organism should possess the right genes to create offspring and to be able to access enough food and resources. Furthermore, the organism needs to be able to reproduce itself in a way that is optimally within its environmental niche.
These elements, along with mutations and gene flow, can lead to an alteration in the ratio of different alleles in the population's gene pool. This change in allele frequency can result in the emergence of novel traits and eventually new species as time passes.
Many of the characteristics we admire in plants and animals are adaptations. For example the lungs or gills which extract oxygen from air feathers and fur for insulation long legs to run away from predators and camouflage for hiding. To understand adaptation, it is important to differentiate between physiological and behavioral traits.
Physical characteristics like large gills and thick fur are physical characteristics. Behavioral adaptations are not an exception, for instance, the tendency of animals to seek companionship or move into the shade in hot temperatures. Additionally it is important to understand that a lack of forethought does not mean that something is an adaptation. Inability to think about the effects of a behavior even if it seems to be rational, may make it inflexible.