DIVERGENT EVOLUTION: CAUSES AND EXAMPLES - BIOLOGY - 2024

The evolution divergent or adaptive radiation is a biological process that describes the accumulation of differences between one or more species, in order to fill different ecological niches (habitat shared by various species).

The second word that makes up the term divergent evolution refers to something that separates or differentiates. Thus, the term refers to the differentiation between species despite their similar or identical origin, and this in turn represents the opposite case of convergent evolution, in which species from different ancestors evolve and finally share different characteristics.

The process of divergent evolution gives way to another biological process called speciation, in which organisms belonging to the same species diversify, giving rise to different species, which still share characteristics with their ancestors, but each one presents new characteristics., which allow them to cover new niches.

The tools that species use during the divergent evolution process are mutation (change in the organization of the DNA of a living being) and natural selection (greater reproduction of a species according to environmental conditions).

Causes of divergent evolution

The divergent evolution process can be classified mainly as a form of adaptation and / or survival of various species of living beings.

Thus, adaptive radiation occurs frequently in situations in which a species is introduced to a new ecosystem, naturally or artificially.

In this way, some causes of evolution in living beings can be differentiated:

- General adaptation

It refers to the process by which a species develops a new ability, which until then it did not possess, which allows it to reach new parts of its environment, that is, it is capable of covering a new ecological niche.

The acquisition of a new ability by a species can occur in turn due to various factors or needs, such as obtaining food, the need for shelter against predators, etc.

A classic example of this is the development and evolution of the ability to fly in birds, which allowed them to explore new places; as well as the evolution of bipedalism (ability to move on the two lower extremities).

- Environmental change

When a species has been able to survive in a considerably or radically changed environment, it will most likely undergo a divergent evolutionary process, to fill new ecological niches created by biological change.

An environmental change is the consequence of one or more factors that generate a series of differences in an ecosystem.

Environmental change can occur due to natural factors, movements of the earth, or natural accidents such as the eruption of a volcano.

An example of adaptive radiation due to environmental change is that of the rapid expansion and development of mammals after the extinction of the dinosaurs, which was partially caused, according to one of the theories, by the impact of a meteorite, asteroid or comet. against the earth, which caused a series of important changes in the environment.

- Isolated ecosystems

The presence of new species in areas with unique ecological characteristics, or difficult to access among various species, as is the case on islands or mountainous areas; and the ability of these species to survive and colonize these areas can give way to a divergent evolutionary process.

An important example of divergent evolution in isolated ecosystems was observed by the English scientist Charles Darwin in the Galapagos Islands.

Here, Darwin observed various species of birds, which had very similar physical characteristics, but with considerable differences in the size and shape of their beaks, which varied according to the food present on each island.

Characteristics for the identification of divergent evolution

- Common ancestor

Since an important characteristic of the presence of divergent evolution is the differentiation of characteristics of various species from the same species, the fact that several species have their roots in the same species is a clear example of divergent evolution.

- A phenotype-environment correlation

Changes in the physical and morphological characteristics of a species will represent an advantage to exploit the environment to which they belong.

That is, these changes will be influenced by the environment, as in the beaks of the birds that Darwin observed.

- Character of utility

Adaptive radiation represents a fundamental means of survival for species. In this way, evolutionary changes will provide an advantage in the performance and / or adaptation of the species in their environment.

Dynamics of divergent evolution

The dynamics or speed of divergent evolution is so fast, that within a short period of time the divergence of various species from one or more species of ancestors occurs. That is, during the time when ecological and phenotypic divergence are underway.

After the proliferation of new genetic combinations, few manage to survive over time, with most of these new species disappearing as quickly as they appeared.

This is a sample of the adaptation process, in which the species that survived are almost completely adapted to the new environment. Furthermore, it is notable that the rise and fall of new species through divergent evolution is occurring slowly, compared to the initial outbreak of species.

This probably occurs because the characteristics of the earth and its environments have remained stable after the geological and climatic changes that occurred in the early history of the planet.

Some examples of divergent evolution

Darwin's finches

Galapagos finches investigated by Darwin

Various evolutionary biologists have determined that fragmented landscapes, such as islands, are main locations where a divergent evolutionary process could occur, due to the disjoint geography of such areas.

When Charles Darwin was in the Galapagos Islands (an archipelago made up of several islands), he observed how between each island there was the presence of different species of the same group of birds known as finches.

Each one of these species presented some differences regarding its size and color; however, the most notable difference between each of these species is the difference in the size of their beaks.

These differences can be explained as a form of adaptation that made it easier for them to obtain food, according to their diet, their peak evolved differently.

Cichlid fish

Cichlid fish are present in the Rift lakes of East Africa. It is estimated that in these lakes there are about 2000 different species of these fish, each of these with different characteristics, such as the size of its body.

These lakes represent a fragmented landscape, similar to the case of the Galapago Islands, which produces isolation between cichlid species, allowing them to evolve separately.

Furthermore, an extraordinary characteristic of cichlids is that many of the cases of divergent evolution among these fish are quite recent.

Hawaiian silver swords

Although the most representative cases of adaptive radiation documented have occurred in animals, such as finches and cichlid fish, divergent evolution can also occur in plants, such as the case of Hawaiian "silver swords."

The so-called Alliance of Hawaiian Silver Swords consists of about 50 species of Hawaiian plants ranging from trees, shrubs or vines; which represents a series of significant differences.

One of the main reasons why divergent evolution occurred in these plants is the fragmented landscape of the Hawaiian Islands.

References

1. Darwin's finch. (2017, May 23). Wikipedia, The Free Encyclopedia. Consultation date: 08:22, July 4, 2017 from es.wikipedia.org
2. Adaptive radiation. (2017, May 5). In Wikipedia, The Free Encyclopedia. Retrieved 08:22, July 4, 2017, from en.wikipedia.org
3. Natural selection. (2017, June 27). Wikipedia, The Free Encyclopedia. Consultation date: 08:22, July 4, 2017 from es.wikipedia.org
4. Speciation. (2017, July 1). In Wikipedia, The Free Encyclopedia. Retrieved 08:23, July 4, 2017, from en.wikipedia.org
5. Divergent evolution. (2017, June 6). In Wikipedia, The Free Encyclopedia. Retrieved 08:23, July 4, 2017, from en.wikipedia.org
6. Speciation. (2015, November 2). Wikipedia, The Free Encyclopedia. Retrieved 08:23, July 4, 2017 from simple.wikipedia.org.