What is Free Evolution?
Free evolution is the notion that natural processes can cause organisms to evolve over time. This includes the creation of new species and transformation of the appearance of existing species.
This has been proven by numerous examples such as the stickleback fish species that can live in salt or fresh water, and walking stick insect species that have a preference for particular host plants. These typically reversible traits cannot explain fundamental changes to the body's basic plans.
Evolution by Natural Selection
The development of the myriad living organisms on Earth is an enigma that has intrigued scientists for decades. The best-established explanation is that of Charles Darwin's natural selection, an evolutionary process that occurs when better-adapted individuals survive and reproduce more successfully than those who are less well adapted. Over time, the population of well-adapted individuals becomes larger and eventually develops into a new species.
Natural selection is a cyclical process that is characterized by the interaction of three factors: variation, inheritance and reproduction. Variation is caused by mutation and sexual reproduction both of which enhance the genetic diversity within a species. Inheritance is the term used to describe the transmission of genetic traits, which include both dominant and recessive genes and their offspring. Reproduction is the production of fertile, viable offspring which includes both asexual and sexual methods.
All of these elements have to be in equilibrium to allow natural selection to take place. For instance the case where a dominant allele at a gene allows an organism to live and reproduce more often than the recessive allele, the dominant allele will become more prevalent in the population. However, if the gene confers a disadvantage in survival or decreases fertility, it will be eliminated from the population. The process is self reinforcing meaning that the organism with an adaptive trait will survive and reproduce far more effectively than those with a maladaptive trait. try this as measured by its capacity to reproduce and survive, is the more offspring it will produce. People with desirable traits, like having a long neck in Giraffes, or the bright white patterns on male peacocks are more likely than others to survive and reproduce and eventually lead to them becoming the majority.
Natural selection only affects populations, not individual organisms. This is a significant distinction from the Lamarckian evolution theory that states that animals acquire traits through the use or absence of use. For instance, if a giraffe's neck gets longer through reaching out to catch prey and its offspring will inherit a longer neck. The length difference between generations will persist until the giraffe's neck becomes too long to no longer breed with other giraffes.
Evolution by Genetic Drift
In genetic drift, the alleles at a gene may attain different frequencies in a population by chance events. In the end, only one will be fixed (become common enough to no longer be eliminated by natural selection) and the rest of the alleles will drop in frequency. In extreme cases, this leads to one allele dominance. The other alleles are eliminated, and heterozygosity is reduced to zero. In a small group it could result in the complete elimination the recessive gene. This is known as the bottleneck effect and is typical of an evolution process that occurs when the number of individuals migrate to form a population.
A phenotypic 'bottleneck' can also occur when the survivors of a disaster such as an outbreak or a mass hunting event are confined to the same area. The surviving individuals will be mostly homozygous for the dominant allele which means that they will all share the same phenotype and will thus have the same fitness traits. This situation might be the result of a war, earthquake or even a cholera outbreak. Regardless of the cause the genetically distinct population that remains could be prone to genetic drift.
Walsh, Lewens and Ariew define drift as a deviation from the expected values due to differences in fitness. They provide a well-known example of twins that are genetically identical, have the exact same phenotype but one is struck by lightning and dies, whereas the other lives and reproduces.
This type of drift can play a very important part in the evolution of an organism. This isn't the only method of evolution. Natural selection is the primary alternative, where mutations and migration keep the phenotypic diversity in a population.
Stephens argues there is a vast difference between treating the phenomenon of drift as a force or cause, and considering other causes, such as selection mutation and migration as forces and causes. He claims that a causal process explanation of drift permits us to differentiate it from other forces, and that this distinction is essential. He argues further that drift has direction, i.e., it tends to eliminate heterozygosity. It also has a size that is determined by population size.
Evolution by Lamarckism
When high school students study biology they are often introduced to the work of Jean-Baptiste Lamarck (1744 - 1829). His theory of evolution, often referred to as "Lamarckism which means that simple organisms evolve into more complex organisms inheriting characteristics that are a product of the use and abuse of an organism. Lamarckism is typically illustrated with a picture of a giraffe that extends its neck to reach the higher branches in the trees. This causes the longer necks of giraffes to be passed on to their offspring who would then grow even taller.
Lamarck was a French Zoologist. 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 introduced a groundbreaking concept that radically challenged the conventional wisdom about organic transformation. In his opinion living things had evolved from inanimate matter via an escalating series of steps. Lamarck wasn't the only one to suggest this however he was widely regarded as the first to offer the subject a thorough and general overview.
The predominant story is that Charles Darwin's theory on natural selection and Lamarckism were competing in the 19th Century. Darwinism eventually won, leading to the development of what biologists today call the Modern Synthesis. This theory denies acquired characteristics can be passed down and instead argues organisms evolve by the selective influence of environmental factors, including Natural Selection.
Lamarck and his contemporaries supported the notion that acquired characters could be passed down to future generations. However, this notion was never a major part of any of their evolutionary theories. This is partly because it was never scientifically tested.
But it is now more than 200 years since Lamarck was born and in the age genomics there is a vast body of evidence supporting the possibility of inheritance of acquired traits. This is referred to as "neo Lamarckism", or more commonly epigenetic inheritance. It is a variant of evolution that is as valid as the more well-known Neo-Darwinian theory.
Evolution by the process of adaptation
One of the most common misconceptions about evolution is being driven by a struggle to survive. This view misrepresents natural selection and ignores the other forces that determine the rate of evolution. The struggle for survival is more accurately described as a struggle to survive within a particular environment, which could include not just other organisms, but as well the physical environment.
To understand how evolution works it is important to consider what adaptation is. Adaptation is any feature that allows living organisms to survive in its environment and reproduce. It could be a physical feature, such as feathers or fur. It could also be a characteristic of behavior such as moving towards 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 and their physical environment, is crucial to its survival. The organism must have the right genes for producing offspring and to be able to access enough food and resources. The organism should also be able to reproduce at an amount that is appropriate for its specific niche.
These factors, together with gene flow and mutations can result in changes in the proportion of different alleles within a population’s gene pool. This change in allele frequency could lead to the development of new traits, and eventually new species in the course of time.
A lot of the traits we appreciate in plants and animals are adaptations. For instance the lungs or gills which draw 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 essential to discern between physiological and behavioral traits.
Physiological adaptations, such as the thick fur or gills are physical characteristics, whereas behavioral adaptations, such as the tendency to search for friends or to move to shade in hot weather, aren't. It is also important to note that the absence of planning doesn't result in an adaptation. In fact, a failure to think about the consequences of a behavior can make it unadaptable, despite the fact that it might appear sensible or even necessary.