Free evolution is the notion that the natural processes of organisms can cause them to develop over time. This includes the appearance and growth of new species.
This has been proven by many examples of stickleback fish species that can thrive in saltwater or fresh water and walking stick insect types that are apprehensive about specific host plants. These mostly reversible traits permutations cannot explain fundamental changes to the body's basic plans.Evolution through Natural Selection
Scientists have been fascinated by the evolution of all living creatures that live on our planet for centuries. The best-established explanation is Charles Darwin's natural selection, which occurs when individuals that are better adapted survive and reproduce more successfully than those less well-adapted. Over time, a population of well-adapted individuals expands and eventually becomes a new species.
Natural selection is a process that is cyclical and involves the interaction of three factors that are: reproduction, variation and inheritance. Variation is caused by mutation and sexual reproduction both of which increase the genetic diversity of the species. Inheritance is the term used to describe the transmission of a person's genetic traits, including both dominant and recessive genes and their offspring. Reproduction is the production of fertile, viable offspring, which includes both sexual and asexual methods.
Natural selection is only possible when all these elements are in equilibrium. For instance when the dominant allele of the gene allows an organism to live and reproduce more often than the recessive one, the dominant allele will be more common within the population. But if the allele confers a disadvantage in survival or reduces fertility, it will be eliminated from the population. The process is self reinforcing which means that an organism with an adaptive trait will survive and reproduce much more than those with a maladaptive trait. The higher the level of fitness an organism has as measured by its capacity to reproduce and survive, is the greater number of offspring it produces. Individuals with favorable traits, like a long neck in giraffes, or bright white color patterns on male peacocks are more likely to others to reproduce and survive which eventually leads to them becoming the majority.
Natural selection is only a force for populations, not individuals. This is a crucial distinction from the Lamarckian evolution theory, which states that animals acquire traits through use or lack of use. If a giraffe expands its neck in order to catch prey and its neck gets longer, then its offspring will inherit this characteristic. The differences in neck size between generations will continue to increase until the giraffe is no longer able to reproduce with other giraffes.
Evolution by Genetic Drift
Genetic drift occurs when alleles of a gene are randomly distributed within a population. In the end, one will attain fixation (become so common that it cannot be removed by natural selection), while other alleles fall to lower frequency. This could lead to a dominant allele in extreme. The other alleles have been basically eliminated and heterozygosity has been reduced to a minimum. In a small number of people this could lead to the complete elimination of recessive gene. This scenario is called the bottleneck effect. It is typical of the evolutionary process that occurs when an enormous number of individuals move to form a population.
A phenotypic 'bottleneck' can also occur when survivors of a disaster like an outbreak or a mass hunting incident are concentrated in the same area. The survivors will share an allele that is dominant and will share the same phenotype. This situation could be caused by war, earthquakes or even a plague. Whatever the reason the genetically distinct group that is left might be prone to genetic drift.
Walsh, Lewens, and Ariew use Lewens, Walsh, and Ariew use a "purely outcome-oriented" definition of drift as any departure from the expected values of differences in fitness. They provide a well-known example of twins that are genetically identical, have identical phenotypes and yet one is struck by lightning and dies, while the other lives and reproduces.
This kind of drift could play a very important role in the evolution of an organism. However, it's not the only method to develop. Natural selection is the main alternative, in which mutations and migrations maintain the phenotypic diversity of the population.
Stephens claims that there is a big difference between treating the phenomenon of drift as a force or a cause and considering other causes of evolution like mutation, selection and migration as causes or causes. He argues that a causal mechanism account of drift permits us to differentiate it from these other forces, and this distinction is crucial. He also argues that drift has a direction: that is it tends to eliminate heterozygosity. It also has a size, that is determined by population size.
Evolution by Lamarckism
Biology students in high school are frequently introduced to Jean-Baptiste Lamarck's (1744-1829) work. His theory of evolution is often referred to as "Lamarckism" and it states that simple organisms develop into more complex organisms through the inherited characteristics that are a result of the organism's natural actions, use and disuse. Lamarckism can be demonstrated by the giraffe's neck being extended 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 grow taller.
Lamarck was a French zoologist and, in his inaugural lecture for his course on invertebrate zoology held at the Museum of Natural History in Paris on 17 May 1802, he introduced a groundbreaking concept that radically challenged the previous understanding of organic transformation. In his view living things had evolved from inanimate matter through the gradual progression of events. Lamarck was not the only one to suggest that this could be the case, but his reputation is widely regarded as having given the subject its first general and comprehensive treatment.
The dominant story is that Charles Darwin's theory of evolution by natural selection and Lamarckism were rivals in the 19th century. Darwinism eventually triumphed and led to the development of what biologists refer to as the Modern Synthesis. The theory argues that acquired traits can be passed down and instead argues organisms evolve by the influence of environment factors, such as Natural Selection.
Although Lamarck believed in the concept of inheritance through acquired characters and his contemporaries offered a few words about this idea however, it was not an integral part of any of their theories about evolution. This is largely due to the fact that it was never tested scientifically.
But it is now more than 200 years since Lamarck was born and in the age of genomics there is a vast body of evidence supporting the heritability of acquired traits. This is also referred to as "neo Lamarckism", or more generally epigenetic inheritance. It is a form of evolution that is just as valid as the more popular Neo-Darwinian model.
Evolution through Adaptation
One of the most commonly-held misconceptions about evolution is that it is being driven by a struggle to survive. This view misrepresents natural selection and ignores the other forces that determine the rate of evolution. The fight for survival is better described as a fight to survive in a particular environment. This can include not only other organisms as well as the physical environment itself.
To understand how evolution operates, it is helpful to consider what adaptation is. Adaptation refers to any particular feature that allows an organism to live and reproduce within its environment. It can be a physical structure like feathers or fur. Or it can be a behavior trait that allows you to move towards shade during the heat, or escaping the cold at night.
The ability of an organism to draw energy from its environment and interact with other organisms, as well as their physical environment, is crucial to its survival. The organism must possess the right genes to create offspring and to be able to access sufficient food and resources. The organism should be able to reproduce itself at an amount that is appropriate for its niche.
These elements, along with gene flow and mutations can result in a shift in the proportion of different alleles within the population's gene pool. Over time, this change in allele frequencies could lead to the emergence of new traits and eventually new species.
Many of the features we find appealing in animals and plants are adaptations. For instance, lungs or Evolutionkr.Kr gills that draw oxygen from air feathers and fur as insulation long legs to run away from predators, and camouflage to hide. To understand the concept of adaptation it is essential to discern between physiological and behavioral traits.
Physical traits such as large gills and thick fur are physical characteristics. The behavioral adaptations aren't, such as the tendency of animals to seek companionship or retreat into shade during 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 effects of a behavior even if it appears to be logical, can make it inflexible.
