Every organism whether it is a plant or an animal belongs to distinct species. A species is a group of organisms that can breed to produce offspring and propagate. The gradual evolution process of species is called speciation and it is believed that it is through natural selection that new species evolve from existing species (Kenneth and Levine). This paper discusses in detail with examples the way in which species undergo changes and new species evolve.
Plants and animals have specific genetic makeup and genes are the chemical structures in the cells that carry the information regarding the genetic makeup of the organism. These genes are responsible for the nature of the organism as it is the genetic material that is passed on from the parents to the offspring. Under some circumstances these genes undergo mutation. The mutation is a process by which there are occasional gene changes that occur inadvertently. From the time this mutation occurs the further generation gets the mutated genes from the parents. In general, it is considered that most mutations result in adversities, however, in some cases, these mutations act as a blessing for the organism and are helpful in better adaptation and make the organism more successful in its life. Organisms that take over that good new gene are most likely to become more abundant and will be able to proliferate.
Over a period of time, the population of a species that has undergone the mutation gets separated by either geography or by climate. As a result of this, the two populations will no longer be able to breed with each other. Further, the two groups undergo change by natural selection in their respective locations and in a totally different manner. Eventually, both these groups evolve in such a way that the two groups are so different that they will not be able to breed and produce offspring. They have become two different species (American Geological Institute).
Based on the distance of separation of the two groups of speciation populations there are basically four modes of natural speciation. These are classified into allopatric, peripatric, parapatric, and sympatric speciation. There also exist techniques to artificially induce speciation by the process of animal husbandry or through laboratory experiments (Boxhorn). In fact even today the process of natural speciation that has a subject of debate. This process of evolution and change in biodiversity has been an interesting subject of research (Baker 303–326).
The disadvantage or the negative part of speciation is that some of the species that are not able to adapt to the changes will be extinct in a few year’s time. There are several such examples that have occurred. In general, the process of speciation makes it impossible to keep up with the population size until no more organisms of that species are left alive further propagation. Biologists have listed several reasons for the extinction of species. For instance, if the environment is under go rapid changes, the species may not be able to adapt to the rapid changes as a result of which they die and the entire population vanishes. There are also instances when the newly evolved species are so much competition that the existing species are not able to survive. However, the most important point to remember here is that the extinction of species is a serious problem because once a species becomes extinct it never appears again (American Geological Institute).
It has been a difficult task to keep a track of species that have already become extinct. Even though biologists are able to identify the species that are undergoing changes, seeing whether the organisms can breed with one another has been a problem for paleontologists. These are the group of people who have more difficulty with fossil species. They can only study the shells or imprints that look almost identical to the present species and then guess that they have a common origin (American Geological Institute).
Allopatric speciation is the type of speciation which occurs when a single population of species separates into two due to the separation by a physical barrier. In general, the two groups will be separated geographically barrier such as a mountain. These isolated populations further undergo changes in their genotype and phenotype when they are exposed to two different and divergent pressures in their respective geographic locations. They also undergo a process known as genetic drift. Over the years even if the two populations come together they will not be able to breed as they have evolved such that they are reproductively isolated and are no longer capable of exchanging genes (pbs.org).
Darwin’s Finches can be taken as a good example of speciation. Charles Darwin visited the Galapagos Islands when he was 26 years old and studies the species diversity. In particular, among the animals he studied were 13 species of finches that were not found in any other parts of the world. Through his research on this species, he found several differences, especially in their beaks. Darwin observed that some of the birds have stout beaks that were used to eat seeds. He also observed another set of finches where the beaks were tailored for eating insects or nectar. He also found a group that has a beak like a woodpecker’s that was mainly used to drill holes in wood. The major distinction from the woodpeckers was that it lacked the long tongue of a true woodpecker. This group used their beaks to dig the insect out. There were also a few that looked more like a warbler than a finch. However, the similarity in the eggs, nest, and courtship behavior helped in their identification of these birds as another group of finches. This is a classic example of allopatric speciation that provided a case study of how a single species reaching the Galapagos from Central or South America changed over a few million years giving rise to the 13 species today. In addition, to the identification of these 13 species of finches, Darwin could also find the major factors that may contribute to speciation (users.rcn.com).
Peripatric speciation takes place when a new species evolve from isolated, small peripheral populations. This occurs mainly because these organisms are not allowed to exchange genes with the main population. It is linked to the idea of a founder effect since small populations frequently experience bottlenecks. Genetic drift is over and over again anticipated to play an important part in peripatric speciation. Though the zones of two diverging populations are separate, sometimes they do overlap (users.rcn.com).
Sympatric speciation is another type of speciation in which species undergo change while they inhabit the same place. Different species of insects have undergone sympatric speciation. Insects that become dependent on different host plants in the same area develop into different species over a period of time. In other words, food habits can also result in the speciation process. The best example of sympatric speciation is that of the cichlids of Lake Nabugabo in East Africa where the speciation has been thought to have occurred due to sexual selection (users.rcn.com).
The process of natural selection leads to speciation. The best example that explains this process is Darwin’s finches. The struggle for existence is very common within a web of ecological relations. Several factors such as the presence of competitors for food resources and space also play a major role. In other words, the entire organism in an ecological food web plays its role in speciation. And in all these cases it can be noted that the competition is between the organisms most closely with other members of their own species, as they have the most similar ecological needs to their own. Simultaneously, all the other species present in the same ecological niche, in decreasing order of ecological similarity, compete and put forth pressure on the organism’s chance of survival. In simple terms, the increasing number of offspring given the limited amounts of resources can ever survive and organisms, therefore, compete for survival. Only those species that are successful competitors will be able to further reproduce and continue their existence. Here the concept of survival of the fittest comes into existence.
The excess productiveness, and resulting competition to survive in every species, provides the preconditions for the natural selection process. Natural selection is mainly based on reproductive behavior, genetics or hereditary factors, the difference in the individual characters, and variation in the fitness of organisms. Based on the evolutionary theory, fitness can be defined as the average number of offspring that are left by an individual when compared to the number of offspring left behind by an average member of the population. It is the individual’s capacity to reproduce and propagate in the population that determines their fitness. If these preconditions are met for any property of a species, natural selection occurs naturally and in the absence, it cannot happen (Natural Selection and Variation).
Work Cited
- American Geological Institute. How do species change over geologic time? AGI Foundation (2008)
- Baker J.M. Adaptive speciation: The role of natural selection in mechanisms of geographic and non-geographic speciation. Studies in History and Philosophy of Biological and Biomedical Sciences (2005). 36: 303–326.
- Boxhorn, J. Observed Instances of Speciation (1995) Web.
- Kenneth, M.R. and Levine Biology: The Living Science. (1998) Pearson Prentice Hall.
- Natural Selection and Variation. Chapter 4. [2008] Web.
- pbs.org Allopatric Speciation [2008] Web.
- users.rcn.com Speciation [2008].