Difference Between Evolution and Speciation

Main Difference – Evolution vs Speciation

Evolution and speciation are two processes of originating new types of organisms with different phenotypes. Evolution brings variations to a population, allowing the population to adapt to the environment. These adaptations allow the population to survive in a particular environment. Evolution is the grand scheme while speciation is a small process which leads to the evolution. The main difference between evolution and speciation is that evolution is the change in the heritable characteristics of a population over successive generations whereas speciation is the formation of a new, distinct species during the process of evolution. 

Key Areas Covered

1. What is Evolution
      – Definition, Features, Types, Examples
2. What is Speciation
      – Definition, Features, Types, Examples
3. What are the Similarities Between Evolution and Speciation
      – Outline of Common Features
4. What is the Difference Between Evolution and Speciation
      – Comparison of Key Differences

Key Terms: Allopatric Speciation, Character Change, Coevolution, Convergent Evolution, Divergent Evolution, Extinction, Parallel Evolution, Parapatric Speciation, Species, Stasis, Sympatric Speciation

What is Evolution

Evolution is the process of continuous branching and diversification of organisms starting from a common ancestor. Two types of evolution can be identified as microevolution and macroevolution.

Microevolution

Microevolution is a type of small scale evolution, which brings changes within a species over a short period. The changes in gene frequency within a small group of organisms or a species cause microevolution. The time can be from one generation to the other. The gene frequencies in a population can be affected by mutations, gene flow, genetic drift, and natural selection. The genes in a population can be randomly mutated. Some genes can also immigrate from other populations. The natural selective reproduction may lead to genetic drift. Finally, the gene frequency of the next generation is decided by natural selection.     

Macroevolution

Major evolutionary changes are referred to as macroevolution. Typically, macroevolution brings changes above the species level. It concerns the evolution of whole taxonomic groups over long periods of time. Origination of mammals, as well as the radiation of flowering plants, are examples of macroevolution. Four patterns of macroevolution can be identified as stasis, character change, speciation, and extinction. In stasis, organisms do not change over a long period of time. Some species are called living fossils since they undergo very few changes. The emergence of additional segments of the body, losing segments and rearrangements can occur in character change. The lineage splitting is referred to as speciation. The frequent speciation produces a bushy tuft of branches of the evolutionary tree. Some lineages may completely disappear from the earth in a process called extinction. Mass extinction is the frequent extinction across many lineages.

Figure 1: Evolutionary tree of life

Four types of macroevolution can be identified as well. They are divergent evolution, convergent evolution, parallel evolution, and coevolution. Divergent evolution is the emergence of two species from a common ancestor under the influence of different selective pressures of the environment. Homologous structures are derived by divergent evolution. Convergent evolution is the emergence of analogous structures by unrelated species under the influence of similar selective pressure of the environment. Parallel evolution is the maintenance of the same level of similarity by several independently evolved species. Coevolution is the exertion of selective pressures on each other by interactive species. The evolutionary tree of life is shown in figure 1. 

What is Speciation

Speciation is the emergence of new, distinct species during the process of evolution. A single evolutionary lineage splits into two or more lineages by the changes in the genetic material of individuals by mutations, gene flow, genetic drift, and natural selection. Ultimately, the two lineages become incapable of interbreeding with each other.  This creates a new species. Speciation can occur through three modes. They are allopatric speciation, parapatric speciation, and sympatric speciation.

Allopatric Speciation

Allopatric speciation is caused by the physical isolation of two populations of the same species by geological barriers such as mountains, deserts, swamps and ice fields. Two populations of same species may start to evolve independently, accumulating mutations, and undergoing genetic drift as well as natural selection. When the two population can no longer interbreed, they are considered as distinct populations. Darwin’s finches are an example of allopatric speciation.  

Parapatric Speciation

Parapatric speciation occurs in a partial geographical separation of two populations of the same species. From time to time, individuals from both populations come into contact. But, heterozygous individuals reduce the fitness of interbreeding.

Sympatric Speciation

Sympatric speciation is the reproductive isolation of two populations within the same geological location. The sympatric speciation occurs as a result of genetic incompatibility between the two populations. The genetic incompatibility arises due to the sexual selection of organisms, which allow the inheritance of only selected characters.

Figure 2: Modes of Speciation

 The different speciation modes are shown in figure 2.

Similarities Between Evolution and Speciation

• Both evolution and speciation are involved in generating new, distinct lineages from pre-existing ones.
• Both evolution and speciation are influenced by the external environment of the organism.

Difference Between Evolution and Speciation

Definition

Evolution: Evolution is the process of continuous branching and diversification of organisms starting from a common ancestor. 

Speciation: Speciation is the formation of new, distinct species during evolution.

Level of Evolution

Evolution: Evolution may occur in both small scale and large scale.

Speciation: Speciation is a type of small scale evolution process.

Duration

Evolution: Evolution occurs during a long period of time.

Speciation: Speciation occurs in a comparatively small period of time.

Types

Evolution: Microevolution and macroevolution are the two types of evolution.

Speciation: Allopatric speciation, parapatric speciation, and sympatric speciation are the three types of speciation.

Causes

Evolution: Evolution is caused by mutations, gene flow, genetic drift, and natural selection.

Speciation: Speciation is caused either by physical or reproductive isolation.

Examples

Evolution: The peppered moth, live birth in three-toed shrinks, arms race between crabs and mussels, Italian wall lizards, cane toad, and Darwin’s finches are examples of evolution.

Speciation: Hawthorn fly, apple maggot, Faeroe Island house mouse, drosophila, ensatina salamanders, and Tennessee cave salamanders are examples of speciation.

Conclusion

Evolution and speciation are two processes which bring changes to organisms. Evolution occurs in both micro and macro level. Gene mutations, gene flow, genetic drift, and natural selection aids the evolution in micro level. Speciation is the generation of two species from a pre-existing species. Evolution is the grand scale level of changes, occurring over a long period of time. Speciation is a small scale change of a population compared to evolution. The main difference between evolution and speciation is the level of changes brought to organisms by each process.

Reference:

1. “Mechanisms of microevolution.” Understanding Evolution. N.p., n.d. Web. Available here. 19 July 2017. 
2.”Patterns in macroevolution.” Understanding Evolution. N.p., n.d. Web. Available here. 19 July 2017. 
3. “Types of Evolution.” Patterns of Evolution. SparkNotes, n.d. Web. Available here. 19 July 2017.  
4. “Speciation.” Encyclopædia Britannica. Encyclopædia Britannica, inc., n.d. Web. Available here. 20 July 2017.  
5. “8 Examples of Evolution in Action.” Listverse. N.p., 18 June 2014. Web. Available here. 20 July 2017. 
6. “Examples of Speciation.” YourDictionary. N.p., 27 July 2016. Web. Available here. 20 July 2017. 

Image Courtesy:

1. “Simplified tree” By Madprime – Own work (CC BY-SA 3.0) via Commons Wikimedia
2. “Speciation modes” (CC BY-SA 3.0) via Commons Wikimedia

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