What is Free Evolution?
Free evolution is the notion that the natural processes of living organisms can lead them to evolve over time. This includes the development of new species and the change in appearance of existing ones.
This has been proven by numerous examples, including stickleback fish varieties that can be found in saltwater or fresh water and walking stick insect types that prefer particular host plants. These mostly reversible trait permutations can't, however, be the reason for fundamental changes in body plans.
Evolution through Natural Selection
Scientists have been fascinated by the development of all the living creatures that inhabit our planet for ages. The most widely accepted explanation is that of Charles Darwin's natural selection process, a process that is triggered when more well-adapted individuals live longer and reproduce more successfully than those that are less well-adapted. Over time, a community of well adapted individuals grows and eventually becomes a new species.
Natural selection is a process that is cyclical and involves the interaction of three factors that are: reproduction, variation and inheritance. Variation is caused by mutation and sexual reproduction both of which increase the genetic diversity of an animal species. Inheritance refers to the passing of a person's genetic characteristics to his or her offspring that includes recessive and dominant alleles. Reproduction is the process of creating fertile, viable offspring. This can be achieved through sexual or asexual methods.
Natural selection only occurs when all these elements are in equilibrium. For example the case where the dominant allele of a gene causes an organism to survive and reproduce more often than the recessive one, the dominant allele will become more prominent within the population. However, if the gene confers an unfavorable survival advantage or reduces fertility, it will disappear from the population. The process is self reinforcing which means that an organism with an adaptive trait will live and reproduce more quickly than those with a maladaptive trait. The more offspring that an organism has the more fit it is which is measured by its capacity to reproduce and survive. People with good traits, like the long neck of giraffes, or bright white patterns on male peacocks, are more likely than others to reproduce and survive which eventually leads to them becoming the majority.
Natural selection only acts on populations, not on individuals. This is a crucial distinction from the Lamarckian evolution theory which holds that animals acquire traits through usage or inaction. For instance, if the animal's neck is lengthened by stretching to reach prey, 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, alleles within a gene can attain different frequencies in a population through random events. At some point, one will attain fixation (become so common that it cannot be removed by natural selection) and the other alleles drop to lower frequency. This could lead to an allele that is dominant in the extreme. The other alleles are eliminated, and heterozygosity decreases to zero. In a small population it could result in the complete elimination of recessive gene. This is known as the bottleneck effect and is typical of the evolution process that occurs when an enormous number of individuals move to form a group.
A phenotypic 'bottleneck' can also occur when survivors of a disaster like an outbreak or a mass hunting event are concentrated in the same area. The surviving individuals will be largely homozygous for the dominant allele, which means that they will all have the same phenotype and will consequently have the same fitness traits. This may be the result of a conflict, earthquake or even a cholera outbreak. Whatever the reason the genetically distinct population that is left might be susceptible to genetic drift.
Walsh Lewens and Ariew use Lewens, Walsh, and Ariew use a "purely outcome-oriented" definition of drift as any deviation from the expected values for differences in fitness. 에볼루션 슬롯 cite a famous instance of twins who are genetically identical, have identical phenotypes and yet one is struck by lightening and dies while the other lives and reproduces.
This type of drift can play a crucial part in the evolution of an organism. It is not the only method for evolution. The main alternative is a process called natural selection, where phenotypic variation in the population is maintained through mutation and migration.
Stephens asserts that there is a big difference between treating drift as a force or a cause and treating other causes of evolution, such as mutation, selection and migration as forces or causes. He claims that a causal process explanation of drift allows us to distinguish it from these other forces, and that this distinction is essential. He further argues that drift is a directional force: that is it tends to eliminate heterozygosity. He also claims that it also has a size, that is determined by the size of 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 is commonly known as "Lamarckism" and it states that simple organisms grow into more complex organisms by the inheritance of traits 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 leaves in the trees. This process would cause giraffes to pass on their longer necks to their offspring, who then become taller.
Lamarck was a French Zoologist. In his lecture to begin his course on invertebrate zoology held at the Museum of Natural History in Paris on the 17th of May in 1802, he presented an original idea that fundamentally challenged the previous understanding of organic transformation. According to him, living things had evolved from inanimate matter through a series of gradual steps. Lamarck wasn't the only one to propose this however he was widely thought of as the first to provide the subject a comprehensive and general overview.
The prevailing story is that Lamarckism grew into an opponent to Charles Darwin's theory of evolution through natural selection and that the two theories battled out in the 19th century. 에볼루션 사이트 prevailed, leading to what biologists refer to as the Modern Synthesis. This theory denies that acquired characteristics can be inherited, and instead, it argues that organisms develop through the selective action of environmental factors, like natural selection.
While Lamarck endorsed the idea of inheritance through 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 partly because it was never tested scientifically.
It's been more than 200 year since Lamarck's birth and in the field of genomics, there is a growing evidence-based body of evidence to support the heritability-acquired characteristics. This is referred to as "neo Lamarckism", or more often epigenetic inheritance. It is a form of evolution that is as valid as the more popular Neo-Darwinian model.
Evolution by Adaptation
One of the most common misconceptions about evolution is that it is a result of a kind of struggle to survive. In fact, this view is inaccurate and overlooks the other forces that determine the rate of evolution. The fight for survival is better described as a struggle to survive in a specific environment. This can include not only other organisms as well as the physical environment.
To understand how evolution operates it is beneficial to think about what adaptation is. The term "adaptation" refers to any specific characteristic that allows an organism to live and reproduce in its environment. It could be a physiological feature, such as feathers or fur, or a behavioral trait such as a tendency to move into shade in the heat or leaving at night to avoid the cold.
An organism's survival depends 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 to generate offspring, and it should be able to access enough food and other resources. The organism should be able to reproduce at the rate that is suitable for its particular niche.
These factors, in conjunction with mutations and gene flow can cause changes in the proportion of different alleles in the population's gene pool. The change in frequency of alleles can lead to the emergence of novel traits and eventually, new species over time.
Many of the features that we admire about animals and plants are adaptations, for example, lungs or gills to extract oxygen from the air, feathers or fur to protect themselves and long legs for running away from predators and camouflage to hide. However, a thorough understanding of adaptation requires attention to the distinction between physiological and behavioral traits.
Physiological adaptations like thick fur or gills are physical characteristics, whereas behavioral adaptations, like the tendency to search for companions or to move into the shade in hot weather, aren't. Furthermore it is important to remember that lack of planning is not a reason to make something an adaptation. In fact, failure to think about the implications of a behavior can make it unadaptive, despite the fact that it might appear reasonable or even essential.