What is Free Evolution?
Free evolution is the notion that natural processes can cause organisms to develop over time. This includes the development of new species and alteration of the appearance of existing species.
A variety of examples have been provided of this, such as different kinds of stickleback fish that can be found in salt or fresh water, as well as walking stick insect varieties that prefer particular host plants. These mostly reversible trait permutations however, are not able to explain fundamental changes in body plans.
Evolution through Natural Selection
Scientists have been fascinated by the development of all living creatures that inhabit our planet for many centuries. The most well-known explanation is that of Charles Darwin's natural selection, an evolutionary process that occurs when individuals that are better adapted survive and reproduce more effectively than those who are less well-adapted. As time passes, the number of well-adapted individuals becomes larger and eventually develops into an entirely new species.
Natural selection is an ongoing process and involves the interaction of 3 factors including reproduction, variation and inheritance. Variation is caused by mutations and sexual reproduction, both of which increase the genetic diversity of an animal species. Inheritance refers to the transmission of a person's genetic traits, which include both dominant and recessive genes to their offspring. Reproduction is the generation of viable, fertile offspring, which includes both asexual and sexual methods.
Natural selection can only occur when all these elements are in equilibrium. If, for example an allele of a dominant gene allows an organism to reproduce and last longer than the recessive gene then the dominant allele will become more prevalent in a group. If the allele confers a negative advantage to survival or lowers the fertility of the population, it will disappear. The process is self-reinforced, meaning that a species with a beneficial trait can reproduce and survive longer than one with an unadaptive trait. The higher the level of fitness an organism has which is measured by its ability to reproduce and endure, is the higher number of offspring it can produce. Individuals with favorable traits, such as longer necks in giraffes or bright white colors in male peacocks, are more likely to survive and produce offspring, which means they will eventually make up the majority of the population in the future.
Natural selection only affects populations, not individuals. This is an important distinction from the Lamarckian theory of evolution which states that animals acquire traits through use or neglect. If a giraffe expands its neck in order to catch prey, and the neck becomes longer, then its offspring will inherit this characteristic. The length difference between generations will continue until the neck of the giraffe becomes so long that it can not breed with other giraffes.
Evolution by Genetic Drift
In genetic drift, alleles of a gene could be at different frequencies within a population through random events. In the end, one will attain fixation (become so widespread that it cannot be removed by natural selection), while other alleles will fall to lower frequency. This could lead to a dominant allele in extreme. Other alleles have been essentially eliminated and heterozygosity has diminished to a minimum. In a small number of people it could result in the complete elimination the recessive gene. Such a scenario would be known as a bottleneck effect and it is typical of evolutionary process that takes place when a lot of individuals move to form a new population.
A phenotypic bottleneck can also occur when survivors of a catastrophe, such as an epidemic or mass hunting event, are concentrated into a small area. The survivors will carry an dominant allele, and will share the same phenotype. This may be caused by a war, an earthquake or even a disease. Whatever the reason the genetically distinct group that remains is prone to genetic drift.
Walsh, Lewens and Ariew define drift as a departure from the expected value due to differences in fitness. They provide the famous case of twins who are genetically identical and share the same phenotype. However one is struck by lightning and dies, while the other is able to reproduce.
This kind of drift can be very important in the evolution of an entire species. This isn't the only method of evolution. The main alternative is a process known as natural selection, in which phenotypic variation in a population is maintained by mutation and migration.
Stephens claims that there is a significant difference between treating drift like an actual cause or force, and considering other causes, such as migration and selection mutation as forces and causes. 에볼루션 바카라 무료체험 claims that a causal process account of drift allows us to distinguish it from other forces, and this distinction is vital. He also argues that drift has a direction: that is it tends to reduce heterozygosity. It also has a size, which is determined by the size of the population.
Evolution by Lamarckism
Biology students in high school are frequently exposed to Jean-Baptiste lamarck's (1744-1829) work. His theory of evolution, often referred to as “Lamarckism” is based on the idea that simple organisms evolve into more complex organisms by adopting traits that result from the organism's use and misuse. Lamarckism is typically illustrated by the image of a giraffe stretching its neck longer to reach the higher branches in the trees. This could cause giraffes to pass on their longer necks to their offspring, who then get 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 the 17th May 1802, he presented an innovative concept that completely challenged the conventional wisdom about organic transformation. In his opinion, living things had evolved from inanimate matter via a series of gradual steps. Lamarck wasn't the only one to suggest this however he was widely regarded as the first to provide the subject a comprehensive and general treatment.
The popular narrative is that Lamarckism became a rival to Charles Darwin's theory of evolutionary natural selection and both theories battled out in the 19th century. Darwinism ultimately won and led to what biologists call the Modern Synthesis. This theory denies acquired characteristics can be passed down through generations and instead argues that organisms evolve through the selective influence of environmental elements, like Natural Selection.
While Lamarck endorsed the idea 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 largely 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 field of genomics there is a growing body of evidence that supports the heritability acquired characteristics. This is sometimes called "neo-Lamarckism" or more frequently, epigenetic inheritance. It is a version of evolution that is as valid as the more well-known Neo-Darwinian model.
Evolution through adaptation
One of the most commonly-held misconceptions about evolution is that it is being driven by a struggle for survival. This is a false assumption and ignores other forces driving evolution. The fight for survival can be better described as a struggle to survive in a particular environment. This could include not only other organisms as well as the physical environment.
Understanding how adaptation works is essential to understand evolution. Adaptation is any feature that allows a living thing to survive in its environment and reproduce. It can be a physiological feature, such as fur or feathers or a behavioral characteristic, such as moving into shade in the heat or leaving at night to avoid cold.
The ability of an organism to draw energy from its surroundings and interact with other organisms, as well as their physical environment is essential to its survival. The organism needs to have the right genes to produce offspring, and it must be able to locate enough food and other resources. The organism must be able to reproduce itself at an amount that is appropriate for its niche.
These factors, together with gene flow and mutation can result in changes in the ratio of alleles (different forms of a gene) in the population's gene pool. As time passes, this shift in allele frequency can result in the emergence of new traits and eventually new species.
Many of the characteristics we admire in plants and animals are adaptations. For example the lungs or gills which extract oxygen from air feathers and fur for insulation, long legs to run away from predators, and camouflage to hide. However, a thorough understanding of adaptation requires attention to the distinction between the physiological and behavioral traits.
Physical traits such as thick fur and gills are physical characteristics. Behavioral adaptations are not like the tendency of animals to seek companionship or to retreat into the shade in hot temperatures. Furthermore, it is important to note that a lack of forethought does not mean that something is an adaptation. A failure to consider the implications of a choice even if it seems to be logical, can cause it to be unadaptive.