Speciation and Evolution

Through the process of reproduction, individuals give rise to new individuals that are similar (not the same) to the parents. This similarity in progeny or offspring or child is due to the transmission of characters or traits from parents to their progeny. The transfer of characters from parents to offspring is known as heredity and the process through which characters or traits pass from one generation to another is called inheritance.

But, according to practical basis offspring are never a true copy of their parents, e.g., in a sugarcane field that are differences among individual plants, similarly in all human beings have different characteristics, complexion, height, eye colors, etc., these differences among the individuals of a species are called variations. Variations in plants are much lesser than in human beings.

The long-term accumulation of variations leads to evolving of a new species and the process is called evolution. It is a complex process and occurs over a long period of time.

Speciation

Speciation is the development of one or more species from an existing species. It occurs when two populations are isolated( both geographically and reproductively) leading to almost no gene flow between the two populations.

However, inbreeding continues within the isolated populations producing more and more generations. Eventually, the members of these two groups will be incapable of reproducing with each other even if they happen to meet. In other generations, the genetic drift accumulates different changes in a subpopulation. Also, natural selection may also operate variably in these different geographic locations. For example, in the territory of one sub-population, crows may get eliminated by eagles.

But this may not be the case in the other sub-population, whereas as a result, the crow numbers will become very high. As an outcome of this, the green variation will not be selected at the first site, while it will be strongly selected at the second.

Together, the process of genetic drift and natural selection may make two isolated sub-populations more and more different from each other. This will lead to the generation of new species.

These new species may be developed:

• If DNA changes are severe enough, such as change in the number of chromosomes, eventually the germ cells of the two groups cannot fuse with each other. 
• If a new variation emerges in which females are only able to mate with a few males due to their specific traits. This allows very strong natural selection for that trait. 

Types of Speciation

1. Allopatric Speciation: In this type of species formation, a part of the population becomes geographically isolated from the main population. An example of Allopatric Speciation is Darwin’s finches which lead to the theory of evolution.
2. Sympatric Speciation: This type of speciation occurs between populations occupying the same geographic range. This type of speciation is common in herbivore insects when a new plant is introduced into a geographic range of species.
3. Parapatric Speciation: It separates adjacent populations. Parapatric speciation takes place when a population of a species enters a new niche or habitat. When a portion of a surrounding has been polluted, the type of speciation that occurs is known as parapatric speciation. Polluted environments include mining activities that leave waste with high amounts of metal such as lead and zinc.

Factors Influencing Speciation

1. Genetic Drift: Genetic drift is also known as the “Sewell Wright Effect”.  It is random in gene(allele) frequency. It occurs only by chance. It is nondirectional. Genetic drift can cause the elimination of certain alleles or fixation of the other alleles in the population. It refers to a change in the population of alleles in the gene pool.
2. Natural Selection: The selection by which organisms are more likely to survive and reproduce is known as Natural Selection. It eventually leads to speciation. Natural selection is the process through which populations of living organisms adapt and change. 
3. Mutation: A mutation is a change in the DNA sequence of an organism. Mutations can result from errors in DNA replication during cell division, exposure to mutagens, or a viral infection.
4. Geographic isolation: The physical separation of members of a population. populations may be physically separated when their original habitat becomes divided. 
5. Recombination: Recombination, the process by which DNA strands are broken and repaired, producing new combinations of alleles, occurs in nearly all multicellular organisms and has important implications for many evolutionary processes.
6. Hybridization: Hybridization occurs almost inevitably during speciation. Moreover, studying patterns of introgression across the genome, and the spatial structure of hybrid zones, can tell us much about the genetics of divergence and reproductive isolation.

Important Characteristics of a Species

The important characteristics of a species may be summarised as follows.

• All the members whether present in one or more populations found in different and even remote areas of the globe are derived from a common ancestor.
• The members resemble one another more than they resemble individuals of other species.
• There is a complete anatomical similarity.
• All the members of a species have a similar karyotype.
• There is a broad similarity in morphological characters.

FAQs on Speciation

Question 1: What is Speciation?

Answer:

Speciation is the splitting of one species into two or more new species or the transformation of one species into a new species over time.

Question 2: What factors could lead to the rise of a new species?

Answer: 

The main factors which lead to the rise of new species are natural selection, genetic drift, geographical isolation, and mutation.

Question 3: What is allopatric speciation? 

Answer:

In this type of species formation, a part of the population becomes geographically isolated from the main population. An example of Allopatric Speciation is Darwin’s finches which lead to the theory of evolution.

Question 4: Which type of speciation is based on the observation of H.L. Carson on Drosophila inhabiting Hawaii islands?

Answer:

Quantum speciation is based on the observation of H.L. Carson.

Question 5: Define Mutation.

Answer: 

A mutation is a change in the DNA sequence of an organism. Mutations can result from errors in DNA replication during cell division, exposure to mutagens, or a viral infection.