What is Free Evolution?
Free evolution is the notion that the natural processes of living organisms can lead to their development over time. This includes the appearance and development of new species.
This has been proven by numerous examples such as the stickleback fish species that can be found in saltwater or fresh water and walking stick insect types that have a preference for specific host plants. These reversible traits 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 living creatures that live on our planet for many centuries. The best-established explanation is Charles Darwin's natural selection, an evolutionary process that is triggered when more well-adapted individuals live longer and reproduce more effectively than those that are less well-adapted. As time passes, a group of well-adapted individuals increases and eventually forms a whole new species.
Natural selection is a process that is cyclical and involves the interaction of three factors including reproduction, variation and inheritance. Variation is caused by mutation and sexual reproduction both of which increase the genetic diversity of a species. Inheritance is the passing of a person's genetic characteristics to his or her offspring which includes both dominant and recessive alleles. Reproduction is the generation of viable, fertile offspring, which includes both asexual and sexual methods.
All of these variables have to be in equilibrium to allow natural selection to take place. If, for example the dominant gene allele allows an organism to reproduce and survive more than the recessive gene The dominant allele will become more prevalent in a group. However, if the gene confers a disadvantage in survival or reduces fertility, it will be eliminated from the population. This process is self-reinforcing meaning that the organism with an adaptive characteristic will live and reproduce much more than those with a maladaptive trait. The more offspring an organism produces, the greater its fitness that is determined by its capacity to reproduce itself and live. People with good traits, such as longer necks in giraffes or bright white color patterns in male peacocks are more likely to survive and produce offspring, and thus will eventually make up the majority of the population over time.
Natural selection only affects populations, not on individuals. This is a major distinction from the Lamarckian theory of evolution that states that animals acquire traits either through use or lack of use. If a giraffe expands its neck in order to catch prey and the neck grows larger, then its children will inherit this characteristic. The difference in neck length between generations will persist until the giraffe's neck gets so long that it can no longer breed with other giraffes.
Evolution by Genetic Drift
Genetic drift occurs when alleles of the same gene are randomly distributed in a group. At some point, one will reach fixation (become so widespread that it is unable to be eliminated through natural selection) and other alleles fall to lower frequency. This could lead to dominance at the extreme. The other alleles have been virtually eliminated and heterozygosity decreased to zero. In a small number of people this could result in the total elimination of the recessive allele. This scenario is called the bottleneck effect. It is typical of the evolutionary process that occurs when the number of individuals migrate to form a group.
A phenotypic bottleneck could occur when survivors of a catastrophe, such as an epidemic or mass hunting event, are condensed within a narrow area. The survivors will have a dominant allele and thus will share the same phenotype. This could be caused by war, earthquake or even a cholera outbreak. Whatever the reason, the genetically distinct population that is left might be prone to genetic drift.
Walsh Lewens, Walsh, and Ariew define drift as a departure from the expected values due to differences in fitness. They provide a well-known example of twins that are genetically identical, have identical phenotypes, but one is struck by lightning and dies, while the other lives and reproduces.
This type of drift can play a significant role in the evolution of an organism. However, it is not the only method to develop. Natural selection is the most common alternative, where mutations and migration keep the phenotypic diversity of the population.
Stephens argues that there is a big difference between treating the phenomenon of drift as a force or as an underlying cause, and considering other causes of evolution, such as selection, mutation and migration as forces or causes. He argues that a causal-process account of drift allows us distinguish it from other forces and this distinction is crucial. He argues further that drift is both direction, 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 Lemarck's (1744-1829) work. His theory of evolution is often referred to as "Lamarckism" and it asserts that simple organisms evolve into more complex organisms by the inheritance of traits that result from the organism's natural actions, use and disuse. Lamarckism is usually illustrated with the image of a giraffe stretching its neck longer to reach leaves higher up in the trees. This causes the longer necks of giraffes to be passed onto their offspring who would grow taller.
Lamarck the French Zoologist from France, presented an innovative idea in his opening lecture at the Museum of Natural History of Paris. He challenged the conventional wisdom on organic transformation. According to Lamarck, living creatures evolved from inanimate materials through a series gradual steps. Lamarck wasn't the first to suggest this but he was regarded as the first to provide the subject a comprehensive and general treatment.
The dominant story is that Charles Darwin's theory of evolution by natural selection and Lamarckism fought during the 19th century. Darwinism eventually triumphed and led to the development of what biologists refer to as the Modern Synthesis. This theory denies acquired characteristics can be passed down through generations and instead argues organisms evolve by the selective influence of environmental elements, like Natural Selection.
While Lamarck supported the notion of inheritance through acquired characters, and his contemporaries also paid lip-service to this notion however, it was not a central element in any of their theories about evolution. This is partly due to the fact that it was never validated scientifically.
It's been more than 200 years since the birth of Lamarck, and in the age genomics there is a growing evidence base that supports the heritability-acquired characteristics. It is sometimes referred to as "neo-Lamarckism" or, more frequently, epigenetic inheritance. This is a model that is as reliable as the popular Neodarwinian model.
Evolution by adaptation
One of the most commonly-held misconceptions about evolution is being driven by a struggle for survival. In fact, this view is inaccurate and overlooks the other forces that drive evolution. The struggle for existence is better described as a struggle to survive in a certain environment. This could include not just other organisms as well as the physical environment itself.
To understand how evolution functions it is important to think about what adaptation is. It refers to a specific characteristic that allows an organism to live and reproduce within its environment. It could be a physiological feature, like feathers or fur or a behavior such as a tendency to move to the shade during hot weather or coming out at night to avoid the cold.
An organism's survival depends on its ability to obtain energy from the environment and to interact with other living organisms and their physical surroundings. The organism should possess the right genes to create offspring and to be able to access sufficient food and resources. Moreover, the organism must be capable of reproducing at a high rate within its environmental niche.
These factors, in conjunction with mutations and gene flow can result in a shift in the proportion of different alleles within the gene pool of a population. As time passes, this shift in allele frequency can result in the emergence of new traits and ultimately new species.
에볼루션 바카라 무료체험 of the traits we admire in plants and animals are adaptations. For example the lungs or gills which draw oxygen from air feathers and fur as insulation and long legs to get away from predators and camouflage to conceal. However, a thorough understanding of adaptation requires paying attention to the distinction between behavioral and physiological traits.
Physiological adaptations like the thick fur or gills are physical traits, while behavioral adaptations, like the tendency to search for friends or to move into the shade in hot weather, are not. In addition it is important to understand that a lack of thought does not make something an adaptation. In fact, a failure to consider the consequences of a behavior can make it unadaptable, despite the fact that it may appear to be sensible or even necessary.