What is Free Evolution KR?
Free evolution is the notion that natural processes can cause organisms to evolve over time. This includes the emergence and development of new species.
This is evident in many examples such as the stickleback fish species that can be found in saltwater or fresh water and walking stick insect species that prefer particular host plants. These are mostly reversible traits, however, cannot explain fundamental changes in body plans.
Evolution by Natural Selection
Scientists have been fascinated by the development of all living organisms that inhabit our planet for many centuries. Charles Darwin's natural selection is the best-established explanation. This happens when those who are better adapted survive and reproduce more than those who are less well-adapted. Over time, the population of well-adapted individuals grows and eventually forms a new species.
Natural selection is an ongoing process and involves the interaction of three factors including reproduction, variation and inheritance. Variation is caused by mutation and sexual reproduction both of which enhance the genetic diversity within a species. Inheritance is the transfer of a person's genetic characteristics to his or her offspring which includes both recessive and dominant alleles. Reproduction is the generation of fertile, viable offspring, which includes both sexual and asexual methods.
All of these variables have to be in equilibrium for natural selection to occur. For instance, if a dominant allele at one gene causes an organism to survive and reproduce more frequently than the recessive allele the dominant allele will become more prominent within the population. If the allele confers a negative advantage to survival or lowers the fertility of the population, it will go away. This process is self-reinforcing meaning that a species that has a beneficial trait is more likely to survive and reproduce than one 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 survive. People with desirable characteristics, like longer necks in giraffes and bright white patterns of color in male peacocks are more likely to survive and have offspring, and thus will become the majority of the population in the future.
Natural selection is only an element in the population and not on individuals. This is a major distinction from the Lamarckian evolution theory that states that animals acquire traits through use or lack of use. If a giraffe expands its neck to catch prey, and the neck becomes longer, then the offspring will inherit this trait. The differences in neck size between generations will increase until the giraffe becomes unable to reproduce with other giraffes.
Evolution by Genetic Drift
Genetic drift occurs when alleles from the same gene are randomly distributed within a population. At some point, one will attain fixation (become so common that it can no longer be eliminated by natural selection) and the other alleles drop to lower frequencies. This can result in a dominant allele in the extreme. The other alleles are eliminated, and heterozygosity decreases to zero. In a small population it could lead to the complete elimination of the recessive allele. This is called a bottleneck effect, and it is typical of the kind of evolutionary process that occurs when a large number of individuals migrate to form a new population.
A phenotypic bottleneck can also occur when the survivors of a disaster such as an outbreak or mass hunt event are confined to an area of a limited size. The survivors will share an allele that is dominant and will share the same phenotype. This can be caused by war, earthquakes or even a plague. The genetically distinct population, if left, 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 both genetically identical and have exactly the same phenotype. However one is struck by lightning and dies, while the other lives to reproduce.
This type of drift can play a very important role in the evolution of an organism. This isn't the only method of evolution. The most common alternative is to use a process known as natural selection, where phenotypic variation in an individual is maintained through mutation and migration.
Stephens claims that there is a vast distinction between treating drift as an actual cause or force, and considering other causes, such as migration and selection mutation as causes and forces. He argues that a causal mechanism account of drift allows us to distinguish it from other forces, and this distinction is essential. He further argues that drift has a direction: that is, it tends to eliminate heterozygosity. It also has a specific magnitude which is determined by the size of population.
Evolution through Lamarckism
When students in high school study biology, they are often introduced to the work of Jean-Baptiste Lamarck (1744 - 1829). His theory of evolution is often called "Lamarckism" and it states that simple organisms grow into more complex organisms through the inheritance of characteristics which result from an organism's natural activities, use and disuse. Lamarckism can be illustrated by a giraffe extending its neck to reach higher levels of leaves in the trees. This would cause giraffes to give their longer necks to their offspring, which then grow even taller.
Lamarck the French Zoologist from France, presented a revolutionary concept in his 17 May 1802 opening lecture at the Museum of Natural History of Paris. He challenged the previous thinking on organic transformation. According to Lamarck, living creatures evolved from inanimate matter by a series of gradual steps. Lamarck was not the first to suggest that this might be the case, but the general consensus is that he was the one giving the subject its first broad and comprehensive treatment.
The predominant story is that Charles Darwin's theory of evolution by natural selection and Lamarckism were rivals in the 19th Century. Darwinism eventually triumphed and led to the creation of 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 factors, such as Natural Selection.
While Lamarck believed in the concept of inheritance by acquired characters, and his contemporaries also paid lip-service to this notion, it was never an integral part of any of their evolutionary theorizing. This is due in part to the fact that it was never validated scientifically.
However, it has been more than 200 years since Lamarck was born and in the age of genomics there is a huge amount of evidence that supports the possibility of inheritance of acquired traits. This is referred to as "neo Lamarckism", or more often epigenetic inheritance. It is a form of evolution that is as relevant as the more popular Neo-Darwinian theory.
Evolution by Adaptation
One of the most popular misconceptions about evolution is being driven by a fight for survival. In reality, this notion is inaccurate and overlooks the other forces that determine the rate of evolution. The struggle for existence is better described as a struggle to survive in a specific environment. This may include not only other organisms, but also the physical environment itself.
To understand how evolution functions it is important to understand what is adaptation. It is a feature that allows a living thing to live in its environment and reproduce. It could be a physical feature, such as feathers or fur. Or it can be a trait of behavior, like moving towards shade during hot weather or moving out to avoid the cold at night.
The ability of an organism to draw energy from its surroundings and interact with other organisms, as well as their physical environments, is crucial to its survival. The organism must have the right genes for producing offspring, and be able to find enough food and resources. The organism should be able to reproduce at an amount that is appropriate for its specific niche.
These elements, along with mutations and gene flow can result in changes in the proportion of different alleles within the population's gene pool. This shift in the frequency of alleles could lead to the development of new traits, and eventually new species in the course of time.
A lot of the traits we admire in plants and animals are adaptations. For example lung or gills that extract oxygen from air, fur and feathers as insulation, long legs to run away from predators and camouflage for hiding. To understand the concept of adaptation it is essential to differentiate between physiological and behavioral characteristics.
Physiological adaptations, like the thick fur or gills are physical traits, whereas behavioral adaptations, like the tendency to search for companions or to retreat into the shade in hot weather, are not. In addition it is important to note that lack of planning does not mean that something is an adaptation. A failure to consider the implications of a choice even if it appears to be logical, can make it unadaptive.