What is Free Evolution?
Free evolution is the concept that natural processes can cause organisms to evolve over time. This includes the appearance and growth of new species.
This is evident in many examples such as the stickleback fish species that can live in salt or fresh water, and walking stick insect species that have a preference for particular host plants. These typically reversible traits cannot explain fundamental changes to the body's basic plans.
Evolution through Natural Selection
The development of the myriad living organisms on Earth is an enigma that has intrigued scientists for many centuries. Charles Darwin's natural selectivity is the best-established explanation. This happens when people who are more well-adapted are able to reproduce faster and longer than those who are less well-adapted. Over time, the population of individuals who are well-adapted grows and eventually develops into an entirely new species.
Natural selection is a cyclical process that is characterized by the interaction of three elements: variation, inheritance and reproduction. Variation is caused by mutation and sexual reproduction both of which increase the genetic diversity within an animal species. Inheritance refers to the passing of a person's genetic characteristics to his or her offspring which includes both recessive and dominant alleles. Reproduction is the generation of fertile, viable offspring, which includes both asexual and sexual methods.
All of these factors have to be in equilibrium for natural selection to occur. If, for example, a dominant gene allele allows an organism to reproduce and survive more than the recessive gene allele then the dominant allele becomes more prevalent in a group. If the allele confers a negative survival advantage or decreases the fertility of the population, it will go away. This process is self-reinforcing meaning that an organism that has a beneficial trait is more likely to survive and reproduce than an individual with a maladaptive trait. The higher the level of fitness an organism has, measured by its ability reproduce and survive, is the more offspring it produces. People with desirable traits, like longer necks in giraffes or bright white colors in male peacocks, are more likely to be able to survive and create offspring, and thus will become the majority of the population in the future.
Natural selection is a factor in populations and not on individuals. This is an important distinction from the Lamarckian theory of evolution which argues that animals acquire traits through use or neglect. For instance, if the animal's neck is lengthened by stretching to reach for prey and its offspring will inherit a longer neck. The differences in neck size between generations will increase until the giraffe is no longer able to breed with other giraffes.
Evolution by Genetic Drift
In the process of genetic drift, alleles within a gene can reach different frequencies in a group by chance events. At some point, only one of them will be fixed (become widespread enough to not longer be eliminated by natural selection), and the other alleles will drop in frequency. In extreme cases it can lead to dominance of a single allele. The other alleles are essentially eliminated, and heterozygosity is reduced to zero. In a small number of people it could lead to the total elimination of recessive alleles. Such a scenario would be known as a bottleneck effect and it is typical of evolutionary process that occurs when a lot of individuals migrate to form a new population.
A phenotypic bottleneck can also occur when the survivors of a catastrophe like an outbreak or mass hunt event are confined to an area of a limited size. The surviving individuals will be largely homozygous for the dominant allele which means that they will all have the same phenotype, and thus share the same fitness characteristics. This can be caused by earthquakes, war or even plagues. Regardless of the cause, the genetically distinct population that is left might be susceptible to genetic drift.
Walsh Lewens, Walsh and Ariew define drift as a departure from expected values due to differences in fitness. They give the famous example of twins who are genetically identical and share the same phenotype. However, one is struck by lightning and dies, while the other continues to reproduce.
This type of drift is vital to the evolution of a species. But, it's not the only method to evolve. The main alternative is to use a process known as natural selection, where the phenotypic variation of a population is maintained by mutation and migration.
Stephens asserts that there is a big distinction between treating drift as a force, or a cause and treating other causes of evolution such as selection, mutation, and migration as forces or causes. He claims that a causal mechanism account of drift permits us to differentiate it from other forces, and that this distinction is vital. He also argues that drift is a directional force: that is it tends to eliminate heterozygosity, and that it also has a magnitude, that is determined by the size of the population.
Evolution through Lamarckism
Biology students in high school are frequently introduced to Jean-Baptiste Lamarck's (1744-1829) work. His theory of evolution is commonly referred to as "Lamarckism" and it states that simple organisms develop into more complex organisms via the inheritance of traits that result from an organism's natural activities use and misuse. 에볼루션 바카라 체험 can be illustrated by a giraffe extending its neck to reach higher levels of leaves in the trees. This could cause the longer necks of giraffes to be passed to their offspring, who would then grow even taller.
Lamarck, a French zoologist, presented a revolutionary concept in his opening lecture at the Museum of Natural History of Paris. He challenged traditional thinking about organic transformation. According to him living things had evolved from inanimate matter through an escalating series of steps. Lamarck wasn't the first to suggest this but he was considered to be the first to provide the subject a thorough and general overview.
The prevailing story is that Lamarckism grew into a rival to Charles Darwin's theory of evolution through natural selection, and that the two theories battled each other in the 19th century. Darwinism eventually prevailed and led to the creation of what biologists today refer to as the Modern Synthesis. The theory denies that acquired characteristics can be passed down through generations and instead, it claims that organisms evolve through the selective action of environment elements, like Natural Selection.
Although Lamarck supported the notion of inheritance by acquired characters, and his contemporaries also paid lip-service to this notion, it was never an integral part of any of their theories about evolution. 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 age genomics, there is an increasing evidence-based body of evidence to support the heritability-acquired characteristics. This is also referred to as "neo Lamarckism", or more commonly epigenetic inheritance. It is a version of evolution that is just as valid as the more popular Neo-Darwinian model.
Evolution through Adaptation
One of the most common misconceptions about evolution is being driven by a struggle to survive. In fact, this view is a misrepresentation of natural selection and ignores the other forces that are driving evolution. The struggle for survival is more accurately described as a struggle to survive within a particular environment, which could be a struggle that involves not only other organisms, but also the physical environment.
To understand how evolution works it is important to understand what is adaptation. The term "adaptation" refers to any characteristic that allows a living organism to live in its environment and reproduce. It can be a physiological structure, like feathers or fur or a behavior such as a tendency to move into the shade in the heat or leaving at night to avoid cold.
The survival of an organism depends on its ability to extract energy from the environment and interact with other living organisms and their physical surroundings. The organism must possess the right genes to generate offspring, and it should be able to find sufficient food and other resources. The organism must also be able reproduce at a rate that is optimal for its particular niche.
These factors, together with gene flow and mutation can result in a change in the proportion of alleles (different forms of a gene) in a population's gene pool. This shift in the frequency of alleles can result in the emergence of novel traits and eventually, new species as time passes.
Many of the features we find appealing in animals and plants are adaptations. For 에볼루션 바카라 체험 or gills that extract oxygen from the air feathers and fur for insulation long legs to run away from predators and camouflage for hiding. However, a complete understanding of adaptation requires paying attention to the distinction between physiological and behavioral characteristics.
Physiological adaptations like the thick fur or gills are physical characteristics, whereas behavioral adaptations, such as the tendency to seek out companions or to move to shade in hot weather, aren't. Furthermore it is important to understand that lack of planning does not mean that something is an adaptation. Failure to consider the implications of a choice, even if it appears to be rational, may cause it to be unadaptive.