What is Free Evolution?
Free evolution is the concept that natural processes can cause organisms to develop over time. This includes the appearance and growth of new species.
Many examples have been given of this, such as different kinds of stickleback fish that can be found in fresh or salt water and walking stick insect varieties that prefer specific host plants. These mostly reversible traits permutations are not able to explain fundamental changes to the body's basic plans.
Evolution by Natural Selection
Scientists have been fascinated by the evolution of all the living creatures that inhabit our planet for ages. Charles Darwin's natural selectivity is the best-established 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, the population of individuals who are well-adapted grows and eventually creates an entirely new species.
무료에볼루션 is an ongoing process that involves the interaction of three factors that are inheritance, variation and reproduction. Sexual reproduction and mutations increase the genetic diversity of the species. Inheritance refers to the transmission of a person's genetic traits, including recessive and dominant genes to their offspring. Reproduction is the process of producing fertile, viable offspring. This can be done via sexual or asexual methods.
All of these variables must be in harmony to allow natural selection to take place. For instance the case where an allele that is dominant at one gene causes an organism to survive and reproduce more often than the recessive allele the dominant allele will be more prevalent in the population. If the allele confers a negative advantage to survival or decreases the fertility of the population, it will go away. The process is self-reinforced, meaning that an organism with a beneficial characteristic is more likely to survive and reproduce than one with an unadaptive trait. The greater an organism's fitness which is measured by its ability to reproduce and endure, is the higher number of offspring it can produce. People with desirable traits, like having a long neck in the giraffe, or bright white color patterns on male peacocks, are more likely than others to live and reproduce which eventually leads to them becoming the majority.
Natural selection only acts on populations, not individuals. This is a significant distinction from the Lamarckian evolution theory which holds that animals acquire traits either through usage or inaction. For instance, if the giraffe's neck gets longer through stretching to reach prey and its offspring will inherit a longer neck. The differences in neck length between generations will persist until the neck of the giraffe becomes too long to no longer breed with other giraffes.
Evolution through Genetic Drift
Genetic drift occurs when alleles from a gene are randomly distributed within a population. At some point, only one of them will be fixed (become common enough that it can no more be eliminated through natural selection), and the other alleles diminish in frequency. In extreme cases this, it leads to one allele dominance. The other alleles are virtually eliminated and heterozygosity decreased to zero. In a small group, this could result in the complete elimination of recessive gene. This scenario is called the bottleneck effect. It is typical of an evolutionary process that occurs whenever an enormous number of individuals move to form a population.
A phenotypic bottleneck can also occur when the survivors of a catastrophe like an outbreak or a mass hunting event are confined to a small area. The surviving individuals will be mostly homozygous for the dominant allele, meaning that they all share the same phenotype and will consequently share the same fitness characteristics. This could be caused by war, earthquakes, or even plagues. Regardless of the cause the genetically distinct population that remains could be susceptible to genetic drift.
Walsh Lewens, Walsh, and Ariew define drift as a departure from expected values due to differences in fitness. They cite a famous example of twins that are genetically identical and have identical phenotypes, but one is struck by lightning and dies, while the other lives and reproduces.
This kind of drift could play a crucial role in the evolution of an organism. But, it's not the only way to evolve. The primary alternative is a process called natural selection, in which phenotypic variation in a population is maintained by mutation and migration.
Stephens claims that there is a huge difference between treating drift like an actual cause or force, and treating other causes like selection mutation and migration as causes and forces. He claims that a causal process account of drift allows us to distinguish it from other forces, and that this distinction is crucial. He further argues that drift is both an orientation, i.e., it tends towards eliminating heterozygosity. It also has a size, that is determined by the size of the population.
Evolution through Lamarckism
In high school, students 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 organism's use and misuse. Lamarckism is illustrated through an giraffe's neck stretching to reach higher levels of leaves in the trees. This could cause giraffes to pass on their longer necks to offspring, who would then grow even taller.
Lamarck was a French zoologist and, in his opening lecture for his course on invertebrate zoology at the Museum of Natural History in Paris on 17 May 1802, he introduced a groundbreaking concept that radically challenged previous thinking about organic transformation. According to Lamarck, living creatures evolved from inanimate matter through a series of gradual steps. Lamarck wasn't the first to propose this, but he was widely regarded as the first to offer the subject a comprehensive and general overview.
The popular narrative is that Lamarckism became an opponent to Charles Darwin's theory of evolution through natural selection, and that the two theories fought it out in the 19th century. Darwinism eventually won, leading to the development of what biologists now refer to as the Modern Synthesis. This theory denies acquired characteristics can be passed down and instead, it claims that organisms evolve through the selective influence of environmental factors, including Natural Selection.
Although Lamarck supported the notion of inheritance by acquired characters and his contemporaries spoke of this idea however, it was not a major feature in any of their evolutionary theories. This is partly because it was never scientifically validated.
It's been more than 200 years since Lamarck was born and, in the age of genomics, there is a large body of evidence supporting the possibility of inheritance of acquired traits. This is sometimes referred to as "neo-Lamarckism" or more frequently, epigenetic inheritance. This is a version that is as valid as the popular Neodarwinian model.
Evolution by adaptation
One of the most commonly-held misconceptions about evolution is its being driven by a struggle to survive. This view is inaccurate and ignores other forces driving evolution. The struggle for existence is better described as a struggle to survive in a specific environment. This may include not only other organisms, but also the physical environment.
Understanding the concept of adaptation is crucial to comprehend evolution. Adaptation refers to any particular characteristic that allows an organism to live and reproduce within its environment. It can be a physical feature, like fur or feathers. Or it can be a characteristic of behavior, like moving towards shade during hot weather or escaping the cold at night.
The capacity 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 needs to have the right genes to generate offspring, and it must be able to locate enough food and other resources. Furthermore, the organism needs to be capable of reproducing itself at an optimal rate within its environment.
These elements, along with gene flow and mutations can cause changes in the proportion of different alleles in the population's gene pool. Over time, this change in allele frequencies could lead to the emergence of new traits and eventually new species.
A lot of the traits we admire in animals and plants are adaptations, for example, the lungs or gills that extract oxygen from the air, fur or feathers to protect themselves long legs to run away from predators, and camouflage for hiding. However, a thorough understanding of adaptation requires a keen eye to the distinction between behavioral and physiological traits.
Physiological traits like thick fur and gills are physical characteristics. Behavioral adaptations are not like the tendency of animals to seek out companionship or move into the shade during hot weather. Furthermore it is important to understand that lack of planning does not make something an adaptation. In fact, a failure to think about the consequences of a behavior can make it unadaptable despite the fact that it might appear reasonable or even essential.