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Free evolution is the concept that the natural processes of living organisms can lead them to evolve over time. This includes the development of new species as well as the alteration of the appearance of existing species.

This is evident in numerous examples such as the stickleback fish species that can be found in saltwater or fresh water and walking stick insect types that are apprehensive about particular host plants. These mostly reversible traits permutations do not explain the fundamental changes in basic body plans.

Evolution by Natural Selection

Scientists have been fascinated by the evolution of all living creatures that inhabit our planet for many centuries. Charles Darwin's natural selectivity is the best-established explanation. This is because those who are better adapted have more success in reproduction and survival than those who are less well-adapted. Over time, a community of well-adapted individuals increases and eventually becomes a new species.

Natural selection is an ongoing process that involves the interaction of three factors: variation, inheritance and reproduction. Variation is caused by mutations and sexual reproduction both of which increase the genetic diversity within an animal species. Inheritance refers the transmission of a person’s genetic traits, including recessive and dominant genes to their offspring. Reproduction is the process of generating viable, fertile offspring. This can be achieved through sexual or asexual methods.

Natural selection is only possible when all these elements are in harmony. For instance, if the dominant allele of a gene can cause an organism to live and reproduce more frequently than the recessive one, the dominant allele will be more common in the population. If the allele confers a negative advantage to survival or decreases the fertility of the population, it will be eliminated. The process is self-reinforcing meaning that an organism with an adaptive characteristic will live and reproduce much more than one with a maladaptive characteristic. The more offspring that an organism has, the greater its fitness, which is measured by its ability to reproduce and survive. Individuals with favorable traits, like a longer neck in giraffes, or bright white colors in male peacocks are more likely survive and produce offspring, and thus will make up the majority of the population in the future.

Natural selection is an aspect of populations and not on individuals. This is an important distinction from the Lamarckian theory of evolution which states that animals acquire traits through use or disuse. If a giraffe extends its neck to reach prey and its neck gets longer, then the children will inherit this characteristic. The differences in neck size between generations will increase until the giraffe becomes unable to breed with other giraffes.

Evolution through Genetic Drift

Genetic drift occurs when alleles of the same gene are randomly distributed in a population. Eventually, only one will be fixed (become widespread enough to not longer be eliminated by natural selection), and the rest of the alleles will diminish in frequency. In the extreme, this leads to one allele dominance. The other alleles are essentially eliminated, and heterozygosity falls to zero. In a small group this could result in the complete elimination of recessive allele. This is known as the bottleneck effect. It is typical of an evolutionary process that occurs whenever the number of individuals migrate to form a group.

A phenotypic bottleneck may occur when survivors of a catastrophe, such as an epidemic or a mass hunting event, are condensed into a small area. The surviving individuals will be largely homozygous for the dominant allele which means they will all share the same phenotype and thus have the same fitness traits. This situation might be caused by a conflict, earthquake or even a cholera outbreak. The genetically distinct population, if it remains vulnerable to genetic drift.

Walsh Lewens, Walsh, and Ariew define drift as a departure from expected values due to differences in fitness. They provide a well-known example of twins that are genetically identical, share identical phenotypes, and yet one is struck by lightning and dies, while the other lives and reproduces.

This type of drift is vital to the evolution of the species. It's not the only method of evolution. The most common alternative is to use a process known as natural selection, where phenotypic variation in an individual is maintained through mutation and migration.

Stephens asserts that there is a significant difference between treating drift like a force or cause, and treating other causes like migration and selection as forces and causes. He argues that a causal-process account of drift allows us separate it from other forces, and this distinction is crucial. He argues further that drift is both direction, i.e., it tends to reduce heterozygosity. It also has a size that is determined by population size.

Evolution by Lamarckism

Biology students in high school are frequently exposed to Jean-Baptiste lamarck's (1744-1829) work. His theory of evolution is generally known as "Lamarckism" and it asserts that simple organisms evolve into more complex organisms through the inherited characteristics which result from the natural activities of an organism, use and disuse. Lamarckism can be demonstrated by an giraffe's neck stretching to reach higher branches in the trees. This would cause giraffes to pass on their longer necks to their offspring, which then get taller.

Lamarck was a French zoologist and, in his opening lecture for his course on invertebrate zoology held 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 had evolved from inanimate matter through a series of gradual steps. Lamarck was not the only one to suggest that this might be the case, but his reputation is widely regarded as giving the subject its first general and thorough treatment.

The prevailing story is that Lamarckism was a rival to Charles Darwin's theory of evolution by natural selection and both theories battled it out in the 19th century. Darwinism eventually prevailed which led to what biologists refer to as the Modern Synthesis. The Modern Synthesis theory denies the possibility that acquired traits can be inherited and instead suggests that organisms evolve by the symbiosis of environmental factors, like natural selection.

Lamarck and his contemporaries endorsed the notion that acquired characters could be passed on to the next generation. However, this idea was never a major part of any of their theories on evolution. This is partly due to the fact that it was never validated scientifically.

It's been more than 200 year since Lamarck's birth, and in the age genomics, there is an increasing evidence base that supports the heritability-acquired characteristics. This is often referred to as "neo-Lamarckism" or, more frequently, epigenetic inheritance. It is a version of evolution that is just as valid as the more popular Neo-Darwinian theory.

Evolution by the process of adaptation

One of the most widespread misconceptions about evolution is that it is driven by a sort of struggle for survival. This view is inaccurate and ignores other forces driving evolution. The fight for survival can be more effectively described as a struggle to survive within a specific environment, which could be a struggle that involves not only other organisms, but also the physical environment itself.


To understand how evolution functions it is beneficial to consider what adaptation is. The term "adaptation" refers to any characteristic that allows a living organism to live in its environment and reproduce. It can be a physical feature, such as feathers or fur. It could also be a behavior trait, like moving towards 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 environment, is crucial to its survival. The organism must possess the right genes to produce offspring and be able find enough food and resources. The organism should also be able reproduce itself at a rate that is optimal for its niche.

These elements, in conjunction with gene flow and mutation can result in a change in the proportion of alleles (different forms of a gene) in the gene pool of a population. This shift in the frequency of alleles can result in the emergence of new traits and eventually new species in the course of time.

???? ??? ?? of the characteristics we admire in animals and plants are adaptations, for example, lungs or gills to extract oxygen from the air, feathers or fur for insulation, long legs for running away from predators, and camouflage to hide. However, a proper understanding of adaptation requires paying attention to the distinction between the physiological and behavioral characteristics.

Physiological adaptations, like thick fur or gills, are physical traits, while behavioral adaptations, such as the desire to find companions or to move to shade in hot weather, are not. Additionally, it is important to understand that lack of planning does not mean that something is an adaptation. Inability to think about the implications of a choice even if it seems to be rational, could cause it to be unadaptive.

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