Free evolution is the notion that natural processes can lead to the development of organisms over time. This includes the emergence and development of new species.
This has been demonstrated by many examples such as the stickleback fish species that can live in saltwater or fresh water and walking stick insect species that are apprehensive about particular host plants. These reversible traits cannot explain fundamental changes to the basic body plan.
Evolution through Natural Selection
Scientists have been fascinated by the development of all the living creatures that inhabit our planet for centuries. Charles Darwin's natural selectivity is the most well-known explanation. This process occurs when individuals who are better-adapted have more success in reproduction and survival 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 involves the interaction of three factors including inheritance, variation, and reproduction. Sexual reproduction and mutation increase the genetic diversity of an animal species. Inheritance refers to the transmission of genetic traits, including both dominant and recessive genes to their offspring. Reproduction is the process of creating viable, fertile offspring. This can be done through sexual or asexual methods.
Natural selection is only possible when all these elements are in harmony. For example when an allele that is dominant at the gene allows an organism to live and reproduce more frequently than the recessive allele the dominant allele will become more prominent within the population. If the allele confers a negative survival advantage or decreases the fertility of the population, it will go away. The process is self-reinforcing meaning that an organism that has an adaptive characteristic will live and reproduce far more effectively than those with a maladaptive trait. The greater an organism's fitness as measured by its capacity to reproduce and endure, is the higher number of offspring it will produce. People with good characteristics, such as a long neck in giraffes, or bright white color patterns on male peacocks are more likely to others to live and reproduce which eventually leads to them becoming the majority.
Natural selection is only a force for populations, not on individuals. This is a significant distinction from the Lamarckian theory of evolution which claims that animals acquire traits through use or neglect. For example, if a giraffe's neck gets longer through reaching out to catch prey its offspring will inherit a more long neck. The difference in neck size between generations will continue to increase until the giraffe becomes unable to reproduce with other giraffes.
Evolution through Genetic Drift
Genetic drift occurs when alleles of a gene are randomly distributed in a population. At some point, only one of them will be fixed (become widespread enough to not longer be eliminated by natural selection) and the other alleles diminish in frequency. This can result in a dominant allele in the extreme. The other alleles have been basically eliminated and heterozygosity has diminished to zero. In a small group it could lead to the total elimination of recessive allele. This scenario is called a bottleneck effect, and it is typical of the kind of evolutionary process that occurs when a large number of individuals move to form a new group.
A phenotypic bottleneck can also occur when the survivors of a disaster such as an outbreak or a mass hunting event are concentrated in the same area. The survivors will carry an allele that is dominant and will share the same phenotype. This may be caused by war, an earthquake, or even a plague. Regardless of the cause, the genetically distinct population that remains is susceptible to genetic drift.Walsh, Lewens, and Ariew use a "purely outcome-oriented" definition of drift as any departure from the expected values for variations in fitness. They give a famous example of twins that are genetically identical, share the exact same phenotype but one is struck by lightening and dies while the other lives and reproduces.
This type of drift can play a crucial role in the evolution of an organism. But, it's not the only way to develop. The primary alternative is a process known as natural selection, in which the phenotypic diversity of the population is maintained through mutation and migration.
Stephens claims that there is a significant distinction between treating 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 allows us to distinguish it from the other forces, and this distinction is vital. He also argues that drift is both a direction, i.e., it tends towards eliminating heterozygosity. It also has a size which is determined based on population size.
Evolution through Lamarckism
When high school students study biology they are often introduced to the work of Jean-Baptiste Lamarck (1744 - 1829). His theory of evolution, commonly referred to as "Lamarckism" which means that simple organisms evolve into more complex organisms through adopting traits that are a product of the use and abuse of an organism. Lamarckism is usually illustrated with the image of a giraffe stretching its neck longer to reach leaves higher up in the trees. This could cause giraffes' longer necks to be passed onto their offspring who would grow 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 17 May 1802, he presented an innovative concept that completely challenged the conventional wisdom about organic transformation. According to Lamarck, living things evolved from inanimate material through a series gradual steps. Lamarck was not the first to propose this, but he was widely thought of as the first to offer the subject a comprehensive and general explanation.
The dominant story is that Charles Darwin's theory on natural selection and Lamarckism were competing during the 19th century. Darwinism eventually prevailed and led to the development of what biologists today call the Modern Synthesis. This theory denies acquired characteristics can be passed down and instead argues that organisms evolve through the selective influence of environmental elements, like Natural Selection.
While Lamarck believed in the concept of inheritance by acquired characters and his contemporaries also spoke of this idea however, it was not a major feature in any of their evolutionary theorizing. This is due to the fact that it was never tested scientifically.
However, it has been more than 200 years since Lamarck was born and, in the age of genomics, there is a large body of evidence supporting the heritability of acquired characteristics. This is also known as "neo Lamarckism", or more often epigenetic inheritance. This is a model that is as valid as the popular neodarwinian model.
Evolution by the process of adaptation
One of the most popular misconceptions about evolution is that it is driven by a sort of struggle to survive. In reality, 에볼루션 this notion misrepresents natural selection and ignores the other forces that drive evolution. The fight for survival can be more precisely described as a fight to survive within a specific environment, which can include not just other organisms, but also the physical environment itself.
Understanding how adaptation works is essential to understand evolution. It is a feature that allows a living organism to live in its environment and reproduce. It can be a physical structure, like feathers or fur. It could also be a behavior trait such as moving into the shade during the heat, or coming out to avoid the cold at night.
The survival of an organism is dependent on its ability to obtain energy from the environment and to interact with other living organisms and their physical surroundings. The organism must possess the right genes for producing offspring and be able find sufficient food and resources. In addition, the organism should be able to reproduce itself at an optimal rate within its environment.
These factors, along with mutation and gene flow can result in a change in the proportion of alleles (different varieties of a particular gene) in a population's gene pool. Over time, this change in allele frequencies could result in the emergence of new traits and eventually new species.
A lot of the traits we admire about animals and plants are adaptations, such as lungs or gills to extract oxygen from the air, fur or feathers to provide insulation long legs to run away from predators, and camouflage to hide. To comprehend adaptation it is crucial to discern between physiological and behavioral traits.
Physiological adaptations, like thick fur or gills are physical traits, while behavioral adaptations, like the tendency to seek out friends or to move into the shade in hot weather, are not. Furthermore it is important to understand that a lack of thought is not a reason to make something an adaptation. Inability to think about the implications of a choice, even if it appears to be logical, can make it inflexible.
