What is ???? ??? ?? ? Free evolution is the notion that natural processes can cause organisms to evolve over time. This includes the creation of new species and the transformation of the appearance of existing species. Many examples have been given of this, such as different kinds of stickleback fish that can live in salt or fresh water, and walking stick insect varieties that are attracted to specific host plants. These reversible traits, however, cannot 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 best-established explanation is Darwin's natural selection process, a process that occurs when better-adapted individuals survive and reproduce more effectively than those less well adapted. Over time, a community of well-adapted individuals expands and eventually becomes a new species. Natural selection is an ongoing process that is characterized by the interaction of three factors including inheritance, variation, and reproduction. Variation is caused by mutation and sexual reproduction, both of which increase the genetic diversity of a species. Inheritance refers to the passing of a person's genetic traits to the offspring of that person which includes both recessive and dominant alleles. Reproduction is the process of producing fertile, viable offspring which includes both asexual and sexual methods. Natural selection only occurs when all of these factors are in harmony. If, for example an allele of a dominant gene causes an organism reproduce and last longer than the recessive gene then the dominant allele is more common in a 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, which means that an organism that has an adaptive trait will survive and reproduce far more effectively than those with a maladaptive feature. The higher the level of fitness an organism has as measured by its capacity to reproduce and survive, is the greater number of offspring it will produce. Individuals with favorable traits, like a longer neck in giraffes, or bright white patterns of color in male peacocks are more likely to survive and have offspring, which means they will become the majority of the population in the future. Natural selection is only a factor in populations and not on individuals. This is a major distinction from the Lamarckian evolution theory that states that animals acquire traits through usage or inaction. If a giraffe expands its neck to catch prey and the neck grows longer, then the offspring will inherit this characteristic. The length difference between generations will persist until the giraffe's neck gets too long that it can no longer breed with other giraffes. Evolution through Genetic Drift Genetic drift occurs when alleles of a gene are randomly distributed in a population. Eventually, only one will be fixed (become widespread enough to not longer be eliminated by natural selection) and the other alleles will diminish in frequency. This can lead to an allele that is dominant in the extreme. The other alleles have been virtually eliminated and heterozygosity been reduced to a minimum. In a small group, this could result in the complete elimination of the recessive gene. This is known as the bottleneck effect and is typical of an 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 mass hunt event are confined to an area of a limited size. The survivors will be mostly homozygous for the dominant allele, which means that they will all share the same phenotype and thus share the same fitness characteristics. This situation could be caused by war, earthquakes, or even plagues. Regardless of the cause the genetically distinct population that is left might be susceptible to genetic drift. Walsh Lewens, Walsh and Ariew define drift as a deviation from the expected value due to differences in fitness. They cite a famous instance of twins who are genetically identical, share identical phenotypes, but one is struck by lightning and dies, while the other lives and reproduces. This kind of drift could play a significant role in the evolution of an organism. However, it is not the only method to evolve. Natural selection is the primary alternative, where mutations and migration keep the phenotypic diversity in a population. Stephens asserts that there is a vast difference between treating drift like an actual cause or force, and considering other causes, such as migration and selection mutation as causes and forces. He claims that a causal-process account of drift allows us distinguish it from other forces and that this distinction is crucial. He argues further that drift has both an orientation, i.e., it tends to eliminate heterozygosity. It also has a size, that is determined by the size of the population. Evolution by Lamarckism Students of biology in high school are frequently introduced to Jean-Baptiste Lamarck's (1744-1829) work. His theory of evolution, often referred to as "Lamarckism which means that simple organisms develop into more complex organisms inheriting characteristics that are a product of the use and abuse of an organism. Lamarckism is usually illustrated with the image of a giraffe that extends its neck to reach the higher branches in the trees. This causes giraffes' longer necks to be passed on to their offspring who would then grow even taller. Lamarck was a French Zoologist. In his lecture to begin his course on invertebrate Zoology at the Museum of Natural History in Paris on 17 May 1802, he presented an original idea that fundamentally challenged previous thinking about organic transformation. In his view, living things had evolved from inanimate matter via the gradual progression of events. Lamarck wasn't the only one to make this claim, but he was widely regarded as the first to provide the subject a comprehensive and general explanation. The dominant story is that Charles Darwin's theory of evolution by natural selection and Lamarckism were rivals in the 19th Century. Darwinism eventually triumphed, leading to the development of what biologists refer to as the Modern Synthesis. The theory argues that acquired characteristics can be acquired through inheritance and instead argues that organisms evolve through the action of environmental factors, including natural selection. While Lamarck supported the notion of inheritance by acquired characters and his contemporaries offered a few words about this idea but it was not a central element in any of their evolutionary theorizing. This is due in part to the fact that it was never tested scientifically. It's been more than 200 years since Lamarck was born and in the age of genomics there is a vast body of evidence supporting the heritability of acquired characteristics. This is referred to as "neo Lamarckism", or more generally epigenetic inheritance. This is a version that is as valid as the popular Neodarwinian model. Evolution through adaptation One of the most common misconceptions about evolution is its being driven by a struggle to survive. This notion is not true and overlooks other forces that drive evolution. The fight for survival can be more accurately described as a struggle to survive in a particular environment. This could include not only other organisms as well as the physical environment itself. To understand how evolution functions it is beneficial to understand what is adaptation. It refers to a specific feature that allows an organism to live and reproduce within its environment. It can be a physiological feature, such as feathers or fur or a behavioral characteristic, such as moving into the shade in hot weather or coming out at night to avoid the cold. The ability of an organism to extract energy from its surroundings and interact with other organisms, as well as their physical environments, is crucial to its survival. The organism should possess the right genes for producing offspring and to be able to access enough food and resources. The organism should also be able reproduce itself at the rate that is suitable for its particular niche. These factors, together with mutation and gene flow result in a change in the proportion of alleles (different forms of a gene) in the gene pool of a population. The change in frequency of alleles can result in the emergence of new traits, and eventually new species over time. A lot of the traits we admire about animals and plants are adaptations, such as the lungs or gills that extract oxygen from the air, feathers or fur to protect themselves long legs to run away from predators and camouflage for hiding. However, a complete understanding of adaptation requires paying attention to the distinction between behavioral and physiological characteristics. Physical characteristics like thick fur and gills are physical characteristics. Behavior adaptations aren't an exception, for instance, the tendency of animals to seek companionship or to retreat into the shade in hot temperatures. It is important to remember that a insufficient planning does not cause an adaptation. In fact, failing to think about the consequences of a behavior can make it unadaptive despite the fact that it may appear to be reasonable or even essential.
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