What is Free Evolution?
Free evolution is the notion that natural processes can lead to the development of organisms over time. This includes the creation of new species and the transformation of the appearance of existing ones.
Many examples have been given of this, including different varieties of stickleback fish that can live in either salt or fresh water, as well as walking stick insect varieties that are attracted to particular host plants. These reversible traits do not explain the fundamental changes in the basic body plan.
Evolution by Natural Selection
The evolution of the myriad living organisms on Earth is an enigma that has fascinated scientists for many centuries. The most widely accepted explanation is that of Charles Darwin's natural selection process, a process that occurs when better-adapted individuals survive and reproduce more successfully than those less well-adapted. Over time, the population of well-adapted individuals grows and eventually forms an entirely new species.
Natural selection is a cyclical process that involves the interaction of three factors that are inheritance, variation and reproduction. Sexual reproduction and mutations increase genetic diversity in a species. Inheritance refers to the passing of a person's genetic characteristics to their offspring that includes recessive and dominant alleles. Reproduction is the generation of fertile, viable offspring which includes both sexual and asexual methods.
All of these factors must be in balance to allow natural selection to take place. For example, if an allele that is dominant at the gene allows an organism to live and reproduce more often than the recessive allele, the dominant allele will become more common in the population. However, if the gene confers a disadvantage in survival or decreases fertility, it will disappear from the population. The process is self-reinforcing, meaning that a species with a beneficial trait can reproduce and survive longer than one with a maladaptive trait. The more offspring an organism can produce, the greater its fitness that is determined by its capacity to reproduce itself and survive. People with desirable traits, like having a long neck in giraffes, or 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 is only an aspect of populations and not on individuals. This is a crucial distinction from the Lamarckian theory of evolution, which states that animals acquire traits either through usage or inaction. 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 size between generations will continue to grow until the giraffe becomes unable to reproduce with other giraffes.
Evolution by Genetic Drift
Genetic drift occurs when alleles of a gene are randomly distributed within a population. Eventually, only one will be fixed (become common enough that it can no more be eliminated through natural selection), and the other alleles will decrease in frequency. This can result in dominance at the extreme. The other alleles are virtually eliminated and heterozygosity decreased to zero. In a small number of people, this could lead to the complete elimination of the recessive allele. This scenario is called the bottleneck effect and is typical of an evolutionary process that occurs whenever an enormous number of individuals move to form a population.
A phenotypic 'bottleneck' can also occur when the survivors of a disaster like an outbreak or a mass hunting incident are concentrated in an area of a limited size. The remaining individuals are likely to be homozygous for the dominant allele, meaning that they all share the same phenotype, and consequently have the same fitness traits. This could be caused by war, earthquakes or even a plague. Whatever the reason the genetically distinct population that remains could be prone to genetic drift.
Walsh, Lewens, and Ariew use Lewens, Walsh and Ariew employ a "purely outcome-oriented" definition of drift as any deviation from the expected values for variations in fitness. They cite a famous example of twins that are genetically identical, share the exact same phenotype and yet one is struck by lightning and dies, while the other lives and reproduces.
This kind of drift could be vital to the evolution of an entire species. But, it's not the only way to develop. Natural selection is the main alternative, in which mutations and migrations maintain phenotypic diversity within a population.
Stephens asserts that there is a huge difference between treating drift like an actual cause or force, and treating other causes like selection mutation and migration as causes and forces. Stephens claims that a causal mechanism account of drift allows us to distinguish it from the other forces, and this distinction is crucial. He also claims that drift has a direction, that is it tends to eliminate heterozygosity, and that it also has a size, which is determined by the size of the population.
Evolution through Lamarckism
Students of biology in high school are frequently exposed to Jean-Baptiste lamarck's (1744-1829) work. His theory of evolution is often referred to as "Lamarckism" and it asserts that simple organisms evolve into more complex organisms via the inheritance of characteristics that are a result of the natural activities of an organism, use and disuse. Lamarckism can be demonstrated by the giraffe's neck being extended to reach higher branches in the trees. This causes the necks of giraffes that are longer to be passed on to their offspring who would then grow even taller.
Lamarck the French Zoologist, introduced an idea that was revolutionary in his 17 May 1802 opening lecture at the Museum of Natural History of Paris. He challenged traditional thinking about organic transformation. In his opinion 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 the general consensus is that he was the one having given the subject its first broad and comprehensive treatment.
The dominant story is that Charles Darwin's theory on natural selection and Lamarckism were rivals in the 19th century. Darwinism eventually prevailed which led to what biologists call the Modern Synthesis. The theory denies that acquired characteristics can be passed down through generations and instead, it claims that organisms evolve through the selective action of environment elements, like Natural Selection.
Lamarck and his contemporaries supported the notion that acquired characters could be passed down to the next generation. However, this idea was never a major part of any of their theories on evolution. This is largely due to the fact that it was never validated scientifically.
But it is now more than 200 years since Lamarck was born and in the age genomics, there is a large amount of evidence that supports the heritability of acquired characteristics. This is often referred to as "neo-Lamarckism" or more commonly epigenetic inheritance. It is a variant of evolution that is just as valid as the more popular Neo-Darwinian model.
Evolution by adaptation
One of the most popular misconceptions about evolution is that it is being driven by a struggle to survive. In fact, this view misrepresents natural selection and ignores the other forces that drive evolution. The fight for survival is better described as a fight to survive in a particular environment. This could include not only other organisms, but also the physical environment itself.
To understand how evolution operates, it is helpful to think about what adaptation is. It refers to a specific characteristic that allows an organism to survive and reproduce in its environment. It could be a physical structure, like feathers or fur. Or it can be a behavior trait such as moving to the shade during the heat, or moving out to avoid the cold at night.
The survival of an organism is dependent on its ability to extract energy from the environment and to interact with other living organisms and their physical surroundings. The organism must have the right genes for producing offspring and to be able to access sufficient food and resources. In addition, the organism should be capable of reproducing at a high rate within its environmental niche.
These factors, in conjunction with gene flow and mutations, can lead to a shift in the proportion of different alleles in the population's gene pool. This change in allele frequency could lead to the development of new traits, and eventually new species as time passes.
Many of the characteristics we admire in animals and plants are adaptations. For original site or gills which extract oxygen from air feathers and fur as insulation and long legs to get away from predators and camouflage for hiding. To understand adaptation it is crucial to differentiate between physiological and behavioral characteristics.
Physiological adaptations, such as thick fur or gills, are physical traits, while behavioral adaptations, like the tendency to seek out companions or to move into the shade in hot weather, aren't. It is also important to keep in mind that lack of planning does not cause an adaptation. In fact, failing to consider the consequences of a choice can render it unadaptive even though it may appear to be reasonable or even essential.