Anagenesis

What is Anagenesis?

Anagenesis is an evolutionary process in which species continue to exist and survive as an interbreeding population. It is also referred to as phyletic transformation and involves evolution within a single lineage. It does not indicate the formation of new species always. It takes thousands and millions of years for a new species to evolve.

Causes of Anagenesis

When speciation transpires as several lineages bifurcate and discontinue interbreeding, a dedicated assemblage may continue to become the original species. The progression and evolution of this group of species without species selection and extinction are referred to as anagenesis.

As per the theory, in an anagenetic evolution, during the event of speciation, the original population tends to quickly increase and hence achieve genetic variation eventually through recombination of genetic material or mutation provided a stable environment. Other contributors having a notable influence on genetic information and phenotype are genetic drift and selection process which can cause a species to be different from previous forms.

On observing evolutionary lineage, two mechanisms need to be considered. One is when there is a change in the genetic information through the interaction of genes between species over a period of time. The second process is speciation which is closely related to cladogenesis.

On the species-level, diversity can be accomplished through anagenesis. As per the punctuated equilibria hypothesis, anagenesis can be rare and the pace at which evolution occurs is accelerated immediately after the division that might lead to cladogenesis. Speciation can be affected by factors such as geographical isolations and hybridization.

The original species is not eliminated but is only transformed into a new species. For eg., the evolution of horse began from a small mammal Eohippus, meaning “dawn horse”. It looked more like a deer than a horse. The change in the overall size and the feet of the horse is observed.

Anagenesis vs Cladogenesis

Anagenesis

Cladogenesis

Anagenesis is the evolution with the lineage. Cladogenesis is the evolution due to the splitting of the lineage.
It is a slow transition of one species to another. The species are rapidly separated into two or more groups.
No geographical barrier is responsible for the process. A geographical barrier is responsible for creating the new species.
The parent species is gradually transformed into a new species and does not exist. The parent species and the new species might exist together unaware of the fact they are evolved from the same species.
For eg., the evolution of giraffe For eg., Darwin’s Finches

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Additional Reading:

Mutation

 

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