What is Free Evolution?
Free evolution is the notion that natural processes can cause organisms to evolve over time. This includes the development of new species as well as the transformation of the appearance of existing ones.
This has been proven by many examples such as the stickleback fish species that can thrive in salt or fresh water, and walking stick insect types that prefer specific host plants. These typically reversible traits cannot explain fundamental changes to the body's basic plans.
Evolution by Natural Selection
The evolution of the myriad living organisms on Earth is an enigma that has intrigued scientists for many centuries. Charles Darwin's natural selection is the best-established explanation. This is because people who are more well-adapted have more success in reproduction and survival than those who are less well-adapted. Over time, a community of well-adapted individuals increases and eventually forms a whole new species.
Natural selection is a process that is cyclical and involves the interaction of 3 factors that are: reproduction, variation and inheritance. Mutation and sexual reproduction increase the genetic diversity of an animal species. Inheritance is the transfer of a person's genetic characteristics to his or her offspring that includes recessive and dominant alleles. Reproduction is the process of producing viable, fertile offspring, which includes both asexual and sexual methods.
All of these factors must be in harmony for natural selection to occur. If, for instance an allele of a dominant gene makes an organism reproduce and survive more than the recessive allele, then the dominant allele is more common in a population. However, if the gene confers an unfavorable survival advantage or decreases fertility, it will be eliminated from the population. The process is self reinforcing meaning that an organism with an adaptive trait will survive and reproduce far more effectively than those with a maladaptive trait. The more offspring an organism can produce, the greater its fitness which is measured by its capacity to reproduce itself and live. Individuals with favorable characteristics, such as having a long neck in Giraffes, or the bright white patterns on male peacocks are more likely than others to live and reproduce, which will eventually lead to them becoming the majority.
Natural selection only acts on populations, not individuals. This is a significant distinction from the Lamarckian theory of evolution, which argues that animals acquire traits through use or disuse. If a giraffe extends its neck to reach prey, and the neck becomes larger, then its offspring will inherit this trait. The difference in neck size between generations will continue to grow until the giraffe becomes unable to reproduce with other giraffes.
Evolution by Genetic Drift
In genetic drift, alleles at a gene may be at different frequencies in a group due to random events. In the end, one will attain fixation (become so common that it cannot be removed by natural selection), while other alleles fall to lower frequencies. In extreme cases this, it leads to a single allele dominance. Other alleles have been essentially eliminated and heterozygosity has diminished to a minimum. In a small population, this could lead to the total elimination of recessive allele. This scenario is known as 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 population.
A phenotypic bottleneck could occur when the survivors of a disaster, such as an epidemic or mass hunting event, are condensed in a limited area. The surviving individuals will be largely homozygous for the dominant allele which means that they will all share the same phenotype, and thus have the same fitness characteristics. This situation could be caused by war, earthquakes or even a plague. Regardless of the cause the genetically distinct group that remains could be susceptible to genetic drift.
Walsh Lewens, Walsh and Ariew define drift as a departure from the expected value due to differences in fitness. They provide the famous case of twins who are genetically identical and have exactly the same phenotype. However one is struck by lightning and dies, while the other is able to reproduce.
This type of drift can play a significant role in the evolution of an organism. This isn't the only method for evolution. Natural selection is the primary alternative, where mutations and migration keep the phenotypic diversity in the population.
Stephens argues that there is a major difference between treating the phenomenon of drift as a force, or an underlying cause, and treating other causes of evolution such as selection, mutation, and migration as forces or causes. Stephens claims that a causal mechanism account of drift permits us to differentiate it from other forces, and this distinction is vital. He also argues that drift is a directional force: that is it tends to eliminate heterozygosity. He also claims that it also has a specific magnitude that is determined by the size of the population.
Evolution through Lamarckism
Biology students in high school are frequently introduced to Jean-Baptiste Lemarck's (1744-1829) work. His theory of evolution, often called "Lamarckism, states that simple organisms transform into more complex organisms adopting traits that result from the use and abuse of an organism. Lamarckism can be illustrated by a giraffe extending its neck to reach higher leaves in the trees. This could cause giraffes' longer necks to be passed to their offspring, who would then grow even taller.
Lamarck the French Zoologist from France, presented a revolutionary concept in his opening lecture at the Museum of Natural History of Paris. He challenged the previous thinking on organic transformation. According to Lamarck, living things evolved from inanimate materials through a series gradual steps. Lamarck was not the only one to suggest that this could be the case but the general consensus is that he was the one giving the subject his first comprehensive and comprehensive treatment.
The dominant story is that Charles Darwin's theory on natural selection and Lamarckism were competing in the 19th century. Darwinism eventually prevailed and led to the creation of what biologists now call the Modern Synthesis. The Modern Synthesis theory denies that acquired characteristics can be inherited and instead, it argues that organisms develop through the action of environmental factors, like natural selection.
Lamarck and his contemporaries believed in the idea that acquired characters could be passed down to future generations. However, this notion was never a key element of any of their theories about evolution. This is partly due to the fact that it was never validated scientifically.
It's been over 200 years since the birth of Lamarck, and in the age genomics, there is an increasing body of evidence that supports the heritability-acquired characteristics. This is also known as "neo Lamarckism", or more often epigenetic inheritance. It is a version of evolution that is just as valid as the more well-known Neo-Darwinian theory.
Evolution through Adaptation
One of the most common misconceptions about evolution is its being driven by a struggle to survive. In fact, this view is a misrepresentation of natural selection and ignores the 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 only other organisms but also the physical surroundings themselves.
To understand how evolution functions it is important to understand what is adaptation. It is a feature that allows living organisms to live in its environment and reproduce. It can be a physiological structure, such as fur or feathers or a behavioral characteristic, such as moving into shade in hot weather or stepping out at night to avoid cold.
The ability of an organism to draw energy from its surroundings and interact with other organisms as well as their physical environments is essential to its survival. The organism must possess the right genes to create offspring, and it must be able to access sufficient food and other resources. The organism must also be able to reproduce itself at an amount that is appropriate for its particular niche.
These elements, in conjunction with gene flow and mutation, lead to changes in the ratio of alleles (different varieties of a particular gene) in the population's gene pool. As time passes, this shift in allele frequency can result in the development of new traits and eventually new species.
Many of the characteristics we admire about animals and plants are adaptations, for example, the lungs or gills that extract oxygen from the air, fur or feathers for insulation and long legs for running away from predators, and camouflage to hide. To comprehend adaptation it is crucial to distinguish between behavioral and physiological characteristics.
Physical characteristics like thick fur and gills are physical traits. Behavioral adaptations are not, such as the tendency of animals to seek out companionship or retreat into shade in hot weather. It is important to keep in mind that lack of planning does not make an adaptation. A failure to consider the effects of a behavior even if it seems to be logical, can make it inflexible.