A Look At The Good And Bad About Free Evolution
What is Free Evolution?
Free evolution is the concept that natural processes can cause organisms to evolve over time. This includes the evolution of new species and alteration of the appearance of existing ones.
Many examples have been given of this, including various kinds of stickleback fish that can live in salt or fresh water, as well as walking stick insect varieties that are attracted to specific host plants. These are mostly reversible traits, however, cannot explain fundamental changes in body plans.
Evolution through Natural Selection
The development of the myriad of living creatures on Earth is an enigma that has intrigued scientists for decades. The most well-known explanation is Darwin's natural selection process, a process that is triggered when more well-adapted individuals live longer and reproduce more successfully than those less well-adapted. Over time, a population of well-adapted individuals increases and eventually creates a new species.
Natural selection is a cyclical process that involves the interaction of three elements that are 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.
All of these variables have to be in equilibrium to allow natural selection to take place. If, for instance an allele of a dominant gene allows an organism to reproduce and last longer than the recessive gene allele The dominant allele is more common in a population. However, if the allele confers a disadvantage in survival or decreases fertility, it will be eliminated from the population. The process is self reinforcing meaning that an organism with an adaptive trait will live and reproduce much more than one with a maladaptive characteristic. The greater an organism's fitness as measured by its capacity to reproduce and endure, is the higher number of offspring it can produce. People with good characteristics, such as having a long neck in the giraffe, or bright white patterns on male peacocks, are more likely than others to reproduce and survive and eventually lead to them becoming the majority.
Natural selection is only a force for populations, not individuals. This is a significant distinction from the Lamarckian evolution theory, which states that animals acquire traits due to the use or absence of use. If a giraffe stretches its neck in order to catch prey and the neck grows longer, then the children will inherit this characteristic. The length difference between generations will persist until the giraffe's neck gets too long to no longer breed with other giraffes.
Evolution by Genetic Drift
In the process of genetic drift, alleles at a gene may be at different frequencies in a group by chance events. In the end, only one will be fixed (become common enough that it can no longer be eliminated through natural selection), and the rest of the alleles will decrease in frequency. In extreme cases it can lead to one allele dominance. Other alleles have been essentially eliminated and heterozygosity has diminished to a minimum. In a small group this could lead to the complete elimination of recessive gene. This is known as the bottleneck effect and is typical of an evolutionary process that occurs whenever an enormous number of individuals move to form a group.
A phenotypic bottleneck may also occur when the survivors of a catastrophe like an outbreak or mass hunt incident are concentrated in an area of a limited size. The survivors will share a dominant allele and thus will have the same phenotype. This situation could be caused by war, earthquakes or even a plague. The genetically distinct population, if left, could be susceptible to genetic drift.
Walsh, Lewens and Ariew define drift as a departure from the expected values due to differences in fitness. They provide the famous case of twins who are both genetically identical and have exactly the same phenotype, but one is struck by lightning and dies, while the other continues to reproduce.
This type of drift can play a crucial role in the evolution of an organism. It's not the only method for evolution. The main alternative is to use a process known as natural selection, in which phenotypic variation in the population is maintained through mutation and migration.
Stephens argues there is a huge difference between treating the phenomenon of drift as an agent or cause and considering other causes, such as migration and selection as forces and causes. He argues that a causal process explanation of drift allows us to distinguish it from other forces, and this distinction is crucial. He also argues that drift has a direction, that is it tends to eliminate heterozygosity. He also claims that it also has a size, which is determined by population size.
Evolution by Lamarckism
When students in high school study biology they are often introduced to the work of Jean-Baptiste Lamarck (1744 - 1829). His theory of evolution, also referred to as "Lamarckism, states that simple organisms develop into more complex organisms through taking on traits that are a product of the use and abuse of an organism. Lamarckism is typically illustrated with a picture of a giraffe stretching its neck further to reach the higher branches in the trees. This would result in giraffes passing on their longer necks to their offspring, which then become taller.
Lamarck the French Zoologist, introduced an innovative idea in his 17 May 1802 opening lecture at the Museum of Natural History of Paris. He challenged the traditional thinking about organic transformation. According to him living things evolved from inanimate matter through the gradual progression of events. Lamarck wasn't the first to make this claim however he was widely thought of as the first to provide the subject a thorough and general overview.
The predominant story is that Charles Darwin's theory of evolution by natural selection and Lamarckism were rivals during the 19th century. Darwinism ultimately prevailed and led to what biologists refer to as the Modern Synthesis. This theory denies acquired characteristics can be passed down through generations and instead, it claims that organisms evolve through the selective influence of environmental factors, including Natural Selection.
Lamarck and his contemporaries supported the idea that acquired characters could be passed on to the next generation. However, this concept was never a central part of any of their theories about evolution. This is partly because it was never tested scientifically.
It has 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 often referred to as "neo-Lamarckism" or, more often epigenetic inheritance. It is a variant of evolution that is as relevant as the more popular neo-Darwinian model.
Evolution by Adaptation
One of the most popular misconceptions about evolution is that it is being driven by a fight for survival. This notion is not true and overlooks other forces that drive evolution. The fight for survival is better described as a struggle to survive in a particular environment. This can be a challenge for not just other living things but also the physical environment itself.
Understanding how adaptation works is essential to comprehend evolution. It is a feature that allows a living organism to survive in its environment and reproduce. It can be a physical structure, such as feathers or fur. Or it can be a trait of behavior, like moving towards shade during the heat, or escaping the cold at night.
The survival of an organism is dependent on its ability to extract energy from the environment and to interact with other living organisms and their physical surroundings. The organism should possess the right genes to produce offspring, and be able to find sufficient food and resources. The organism must also be able reproduce itself at the rate that is suitable for its niche.
These elements, in conjunction with gene flow and mutation result in a change in the proportion of alleles (different varieties of a particular gene) in a population's gene pool. As time passes, this shift in allele frequencies could result in the emergence of new traits and ultimately new species.
A lot of the traits we find appealing in plants and animals are adaptations. For example, lungs or gills that extract oxygen from the air feathers and fur for insulation and long legs to get away from predators and camouflage for hiding. However, a complete understanding of adaptation requires paying attention to the distinction between physiological and behavioral traits.
Physiological adaptations, like the thick fur or gills are physical characteristics, whereas behavioral adaptations, such as the desire to find companions or to retreat to shade in hot weather, are not. Furthermore it is important to remember that a lack of forethought does not make something an adaptation. In 무료 에볼루션 , a failure to think about the implications of a behavior can make it unadaptable, despite the fact that it might appear logical or even necessary.