What is Free Evolution?
Free evolution is the concept that the natural processes that organisms go through can lead to their development over time. This includes the appearance and development of new species.
This has been proven by numerous examples of stickleback fish species that can be found in saltwater or fresh water and walking stick insect varieties that have a preference for specific host plants. These reversible traits can't, however, be the reason for fundamental changes in body plans.
Evolution by Natural Selection
Scientists have been fascinated by the development of all living organisms that inhabit our planet for many centuries. The best-established explanation is that of Charles Darwin's natural selection, a process that is triggered when more well-adapted individuals live longer and reproduce more effectively than those that are less well-adapted. As time passes, the number of individuals who are well-adapted grows and eventually develops into a new species.
Natural selection is an ongoing process and involves the interaction of three factors: variation, reproduction and inheritance. Sexual reproduction and mutation increase genetic diversity in a species. Inheritance refers the transmission of a person’s genetic traits, including both dominant and recessive genes and their offspring. Reproduction is the generation of viable, fertile offspring, which includes both sexual and asexual methods.
Natural selection only occurs when all the factors are in equilibrium. For instance the case where the dominant allele of one gene can cause an organism to live and reproduce more often than the recessive allele the dominant allele will become more common in the population. If the allele confers a negative advantage to survival or lowers the fertility of the population, it will disappear. The process is self reinforcing which means that an organism that has an adaptive characteristic will live and reproduce far more effectively than those with a maladaptive feature. The more offspring that an organism has the more fit it is that is determined by its ability to reproduce itself and survive. People with good traits, like a longer neck in giraffes, or bright white patterns of color in male peacocks are more likely to survive and have offspring, which means they will become the majority of the population in the future.
Natural selection only acts on populations, not on individuals. This is a significant distinction from the Lamarckian theory of evolution which holds that animals acquire traits due to the use or absence of use. For instance, if the giraffe's neck gets longer through stretching to reach for prey and its offspring will inherit a larger neck. The length difference between generations will persist until the neck of the giraffe becomes too long to not breed with other giraffes.
Evolution through Genetic Drift
Genetic drift occurs when the alleles of the same gene are randomly distributed within a population. Eventually, one of them will attain fixation (become so common that it can no longer be eliminated through natural selection) and other alleles fall to lower frequency. In the extreme it can lead to one allele dominance. The other alleles have been virtually eliminated and heterozygosity diminished to a minimum. In a small group it could lead to the total elimination of recessive alleles. This scenario is called a bottleneck effect, and it is typical of the kind of evolutionary process that occurs when a large amount of individuals move to form a new group.
A phenotypic bottleneck can also happen when the survivors of a catastrophe like an epidemic or a massive hunting event, are condensed in a limited area. The remaining individuals will be largely homozygous for the dominant allele meaning that they all share the same phenotype and therefore have the same fitness characteristics. This can be caused by war, earthquakes or even a plague. The genetically distinct population, if it is left susceptible to genetic drift.
Walsh Lewens, Walsh and Ariew define drift as a deviation from expected values due to differences in fitness. They give a famous instance of twins who are genetically identical, share identical phenotypes but one is struck by lightening and dies while the other lives and reproduces.
This kind of drift could play a very important part in the evolution of an organism. It is not the only method of evolution. The most common alternative is to use a process known as natural selection, where the phenotypic diversity of the population is maintained through mutation and migration.
Stephens argues there is a huge distinction between treating drift as an actual cause or force, and treating other causes such as selection mutation and migration as causes and forces. 에볼루션 무료 바카라 claims that a causal process account of drift allows us distinguish it from other forces and this distinction is essential. He argues further that drift is both a direction, i.e., it tends towards eliminating heterozygosity. It also has a size, which is determined by population size.
Evolution by Lamarckism
When high school students study biology, they are often introduced to the work of Jean-Baptiste Lamarck (1744 - 1829). His theory of evolution is commonly known as "Lamarckism" and it states that simple organisms develop into more complex organisms through the inherited characteristics that result from the organism's natural actions, use and disuse. Lamarckism can be illustrated by a giraffe extending its neck to reach higher levels of leaves in the trees. This could cause the necks of giraffes that are longer to be passed to their offspring, who would then grow even taller.
Lamarck was a French zoologist and, in his lecture to begin his course on invertebrate zoology at the Museum of Natural History in Paris on 17 May 1802, he introduced an innovative concept that completely challenged the conventional wisdom about organic transformation. According Lamarck, living organisms evolved from inanimate material by a series of gradual steps. Lamarck was not the only one to suggest that this could be the case but the general consensus is that he was the one giving the subject its first general and thorough treatment.
The dominant story is that Charles Darwin's theory on evolution by natural selection and Lamarckism were competing 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 argues organisms evolve by the selective influence of environmental factors, including Natural Selection.
Although Lamarck endorsed the idea of inheritance through acquired characters and his contemporaries also offered a few words about this idea but it was not a major feature in any of their evolutionary theories. This is due to the fact that it was never scientifically validated.
But it is now more than 200 years since Lamarck was born and, in the age of genomics, there is a large amount of evidence to support the heritability of acquired characteristics. This is referred to as "neo Lamarckism", or more generally epigenetic inheritance. This is a variant that is as valid as the popular neodarwinian model.
Evolution by the process of 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 can be better described as a struggle to survive in a particular environment. This may be a challenge for not just other living things, but also the physical environment.
To understand how evolution works, it is helpful to consider what adaptation is. It is a feature that allows living organisms to survive in its environment and reproduce. It can be a physical feature, like feathers or fur. Or it can be a characteristic of behavior that allows you to move to the shade during the heat, 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 essential to its survival. The organism must have the right genes to produce offspring and be able find sufficient food and resources. The organism should also be able to reproduce at a rate that is optimal for its specific niche.
These factors, together with gene flow and mutations, can lead to an alteration in the ratio of different alleles in the population's gene pool. This change in allele frequency could lead to the development of new traits, and eventually new species as time passes.
Many of the features that we admire about animals and plants are adaptations, for example, lungs or gills to extract oxygen from the air, feathers or fur to protect themselves, long legs for running away from predators and camouflage to hide. To understand the concept of adaptation, it is important to differentiate between physiological and behavioral characteristics.
Physical characteristics like the thick fur and gills are physical traits. The behavioral adaptations aren't, such as the tendency of animals to seek companionship or to retreat into the shade in hot weather. It is also important to remember that a the absence of planning doesn't cause an adaptation. A failure to consider the consequences of a decision, even if it appears to be rational, may make it unadaptive.