What is Free Evolution?
Free evolution is the idea that natural processes can cause organisms to evolve over time. This includes the appearance and development of new species.
Many examples have been given of this, including different varieties of fish called sticklebacks that can live in either fresh or salt water and walking stick insect varieties that are attracted to particular host plants. These typically reversible traits cannot explain fundamental changes to the body's basic plans.
Evolution by Natural Selection
Scientists have been fascinated by the evolution of all the living organisms that inhabit our planet for centuries. Charles Darwin's natural selection theory is the best-established explanation. This is because those who are better adapted survive and reproduce more than those who are less well-adapted. Over time, a community of well adapted individuals grows and eventually creates a new species.
Natural selection is a cyclical process that involves the interaction of three factors that are inheritance, variation and reproduction. Sexual reproduction and mutation increase genetic diversity in a species. Inheritance refers to the passing of a person's genetic characteristics to their offspring, which includes both dominant and recessive alleles. Reproduction is the production of viable, fertile offspring, which includes both sexual and asexual methods.
All of these variables must be in balance for natural selection to occur. For instance when a dominant allele at a gene causes an organism to survive and reproduce more often than the recessive one, the dominant allele will become more prominent in the population. If the allele confers a negative advantage to survival or lowers the fertility of the population, it will go away. The process is self reinforcing meaning that an organism with an adaptive trait will live and reproduce much more than those with a maladaptive trait. The more fit an organism is, measured by its ability reproduce and endure, is the higher number of offspring it will produce. People with desirable characteristics, such as the long neck of giraffes, or bright white color patterns on male peacocks, are more likely than others to reproduce and survive which eventually leads to them becoming the majority.
Natural selection only acts on populations, not on individual organisms. This is a crucial distinction from the Lamarckian theory of evolution which holds that animals acquire traits due to usage or inaction. For instance, if the giraffe's neck gets longer through reaching out to catch prey, its offspring will inherit a longer neck. The differences in neck length between generations will persist until the giraffe's neck gets so long that it can not breed with other giraffes.
Evolution through Genetic Drift
In genetic drift, alleles of a gene could attain different frequencies in a population by chance events. At some point, one will reach fixation (become so common that it cannot be eliminated by natural selection) and other alleles will fall to lower frequency. This could lead to a dominant allele in the extreme. The other alleles are eliminated, and heterozygosity is reduced to zero. In a small population, this could lead to the total elimination of the recessive allele. This scenario is called a bottleneck effect, and it is typical of the kind of evolutionary process that takes place when a large number of people migrate to form a new group.
A phenotypic bottleneck may happen when the survivors of a catastrophe like an epidemic or mass hunting event, are condensed within a narrow area. The survivors will carry a dominant allele and thus will share the same phenotype. This can be caused by earthquakes, war, or even plagues. The genetically distinct population, if left vulnerable to genetic drift.
Walsh Lewens, Walsh, and Ariew define drift as a deviation 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 is able to reproduce.
This kind of drift could play a significant role in the evolution of an organism. This isn't the only method of evolution. The most common alternative is to use a process known as natural selection, in which the phenotypic variation of an individual is maintained through mutation and migration.
Stephens argues there is a significant distinction between treating drift as an actual cause or force, and treating other causes like selection mutation and migration as causes and forces. He argues that a causal-process explanation of drift lets us differentiate it from other forces and this differentiation is crucial. visit this site claims that drift is a directional force: that is, it tends to eliminate heterozygosity, and that it also has a specific magnitude that is determined by population size.
Evolution by Lamarckism
When high school students take biology classes, they are frequently introduced to the work of Jean-Baptiste Lamarck (1744 - 1829). His theory of evolution is commonly called "Lamarckism" and it states that simple organisms develop into more complex organisms via the inheritance of characteristics that result from the natural activities of an organism usage, use and disuse. Lamarckism is illustrated through an giraffe's neck stretching to reach higher branches in the trees. This process would result in giraffes passing on their longer necks to offspring, which then get taller.
Lamarck was a French Zoologist. In his opening lecture for his course on invertebrate zoology at the Museum of Natural History in Paris on the 17th May 1802, he introduced a groundbreaking concept that radically challenged previous thinking about organic transformation. In his opinion living things evolved from inanimate matter through an escalating series of steps. Lamarck was not the first to suggest that this might be the case but his reputation is widely regarded as giving the subject its first general and comprehensive treatment.
The most popular story is that Lamarckism was an opponent to Charles Darwin's theory of evolution by natural selection, and that the two theories battled it out in the 19th century. Darwinism ultimately won, leading to what biologists refer to as the Modern Synthesis. The Modern Synthesis theory denies the possibility that acquired traits can be acquired through inheritance and instead suggests that organisms evolve by the symbiosis of environmental factors, such as natural selection.
Lamarck and his contemporaries endorsed the idea that acquired characters could be passed on to future generations. However, this concept was never a central part of any of their theories on evolution. This is partly because it was never tested scientifically.
But it is now more than 200 years since Lamarck was born and in the age genomics there is a huge body of evidence supporting the heritability of acquired characteristics. This is also known as "neo Lamarckism", or more often epigenetic inheritance. It is a variant of evolution that is just as valid as the more well-known neo-Darwinian model.
Evolution through the process of adaptation
One of the most popular misconceptions about evolution is that it is driven by a type of struggle for survival. This is a false assumption and overlooks other forces that drive evolution. The fight for survival can be more precisely described as a fight to survive within a particular environment, which can involve not only other organisms but as well the physical environment.
Understanding how adaptation works is essential to comprehend evolution. Adaptation refers to any particular feature that allows an organism to survive and reproduce within its environment. It could be a physical feature, like feathers or fur. Or it can be a trait of behavior that allows you to move into the shade during hot weather or moving out to avoid the cold at night.
The ability of an organism to draw energy from its surroundings and interact with other organisms and their physical environment is essential to its survival. The organism must possess the right genes to produce offspring and be able find sufficient food and resources. The organism must also be able reproduce at the rate that is suitable for its particular niche.
These factors, together with mutation and gene flow can result in an alteration in the percentage of alleles (different varieties of a particular gene) in the population's gene pool. The change in frequency of alleles can lead to the emergence of new traits, and eventually, new species in the course of time.
Many of the features we appreciate in animals and plants are adaptations. For example, lungs or gills that extract oxygen from air feathers and fur for insulation and long legs to get away from predators and camouflage for hiding. However, a proper understanding of adaptation requires a keen eye to the distinction between the physiological and behavioral traits.
Physiological adaptations like the thick fur or gills are physical traits, whereas behavioral adaptations, like the desire to find friends or to move into the shade in hot weather, are not. It is also important to remember that a the absence of planning doesn't make an adaptation. In fact, a failure to think about the consequences of a choice can render it unadaptable, despite the fact that it may appear to be reasonable or even essential.