What is Free Evolution?
Free evolution is the idea that natural processes can cause organisms to develop 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 be found in salt or fresh water, and walking stick insect types that prefer specific host plants. These reversible traits cannot explain fundamental changes to the basic body plan.
Evolution through Natural Selection
The development of the myriad living organisms on Earth is a mystery that has fascinated scientists for decades. Charles Darwin's natural selection is the most well-known explanation. This happens when people who are more well-adapted have more success in reproduction and survival than those who are less well-adapted. Over time, a population of well adapted individuals grows and eventually creates a new species.
Natural selection is an ongoing process that involves the interaction of three factors that are inheritance, variation and reproduction. Variation is caused by mutation and sexual reproduction, both of which increase the genetic diversity within an animal species. Inheritance is the passing of a person's genetic traits to their offspring which includes both dominant and recessive alleles. Reproduction is the process of creating fertile, viable offspring. This can be achieved by both asexual or sexual methods.
All of these elements must be in harmony for natural selection to occur. If, for instance the dominant gene allele causes an organism reproduce and live longer than the recessive allele The dominant allele is more prevalent in a group. But if the allele confers a disadvantage in survival or decreases fertility, it will disappear from the population. The process is self-reinforcing, which means that an organism that has an adaptive characteristic will live and reproduce more quickly than those with a maladaptive feature. The more offspring that an organism has, the greater its fitness that is determined by its ability to reproduce and survive. People with good traits, like having a longer neck in giraffes or bright white colors in male peacocks, are more likely to be able to survive and create offspring, so they will become the majority of the population over time.
Natural selection is only a force for populations, not on individuals. This is a significant distinction from the Lamarckian evolution theory which holds that animals acquire traits due to use or lack of use. If a giraffe stretches its neck to catch prey, and the neck becomes longer, then its offspring will inherit this characteristic. The difference in neck length between generations will continue until the giraffe's neck becomes too long that it can not breed with other giraffes.
Evolution by Genetic Drift
In genetic drift, the alleles at a gene may be at different frequencies in a group through random events. Eventually, only one will be fixed (become widespread enough to not longer be eliminated through natural selection), and the other alleles diminish in frequency. This can lead to a dominant allele in extreme. The other alleles are basically eliminated and heterozygosity has diminished to zero. In a small group, this could result in the complete elimination of the recessive gene. This scenario is called a bottleneck effect, and it is typical of the kind of evolutionary process that occurs when a lot of individuals move to form a new group.
A phenotypic bottleneck may occur when the survivors of a catastrophe, such as an epidemic or a massive hunting event, are condensed into a small area. The survivors will share an allele that is dominant and will share the same phenotype. This can be caused by earthquakes, war or even plagues. Regardless of the cause the genetically distinct population that remains is prone 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 that are genetically identical and have exactly the same phenotype, but one is struck by lightning and dies, whereas the other continues to reproduce.
This kind of drift could play a significant part in the evolution of an organism. This isn't the only method of evolution. The main 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 big difference between treating the phenomenon of drift as a force or as an underlying cause, and considering other causes of evolution like selection, mutation, and migration as forces or causes. He argues that a causal process account of drift allows us to distinguish it from other forces, and that this distinction is vital. He argues further that drift has both an orientation, i.e., it tends to reduce heterozygosity. 에볼루션 바카라 체험 has a size which is determined by population size.
Evolution by Lamarckism
Biology students in high school are often introduced to Jean-Baptiste Lemarck's (1744-1829) work. His theory of evolution, commonly referred to as "Lamarckism is based on the idea that simple organisms transform into more complex organisms by taking on traits that are a product of the use and abuse of an organism. Lamarckism is illustrated through a giraffe extending its neck to reach higher leaves in the trees. This could cause giraffes to pass on their longer necks to their offspring, who would then get taller.
Lamarck the French Zoologist, introduced a revolutionary concept in his opening lecture at the Museum of Natural History of Paris. He challenged conventional wisdom on organic transformation. According Lamarck, living organisms evolved from inanimate material through a series gradual steps. Lamarck wasn't the first to make this claim, but he was widely considered to be the first to provide the subject a thorough and general explanation.
The predominant story is that Charles Darwin's theory on natural selection and Lamarckism fought in the 19th Century. Darwinism eventually triumphed and led to the development of what biologists now refer to as the Modern Synthesis. The theory argues that acquired traits can be passed down through generations and instead argues that organisms evolve through the selective action of environment factors, such as Natural Selection.
Lamarck and his contemporaries supported the idea that acquired characters could be passed down to the next generation. However, this notion was never a major part of any of their theories on evolution. This is partly because it was never tested scientifically.
It's been more than 200 years since the birth of Lamarck and in the field of genomics, there is a growing evidence-based body of evidence to support the heritability-acquired characteristics. This is also known as "neo Lamarckism", or more generally epigenetic inheritance. It is a version of evolution that is as valid as the more popular Neo-Darwinian theory.
Evolution by adaptation
One of the most common misconceptions about evolution is that it is a result of a kind of struggle to survive. This notion is not true and overlooks other forces that drive evolution. The fight for survival can be more precisely described as a fight to survive within a particular environment, which could include not just other organisms but also the physical environment.
To understand how evolution operates, it is helpful to understand what is adaptation. It is a feature that allows a living thing to survive in its environment and reproduce. It can be a physical structure, like fur or feathers. Or it can be a trait of behavior such as moving to 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 extract energy from the environment and interact with other organisms and their physical environments. The organism must have the right genes for producing offspring and be able find enough food and resources. Furthermore, the organism needs to be able to reproduce itself at a high rate within its environment.
These elements, along with gene flow and mutations, can lead to a shift in the proportion of different alleles within the population's gene pool. Over time, this change in allele frequency can result in the emergence of new traits and ultimately new species.
Many of the characteristics we find appealing in animals and plants are adaptations. For example lung or gills that extract oxygen from the air feathers and fur for insulation, long legs to run away from predators and camouflage to conceal. However, a thorough understanding of adaptation requires attention to the distinction between the physiological and behavioral characteristics.
Physical traits such as large gills and thick fur are physical traits. The behavioral adaptations aren't like the tendency of animals to seek companionship or move into the shade during hot weather. It is important to note that insufficient planning does not result in an adaptation. Inability to think about the implications of a choice, even if it appears to be rational, could make it inflexible.