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.
This states that a species undergoes very little to no change for thousands of years. This is known as stasis. Speciation occurs when a population splits into two due to some geographical events. These two populations diverge from one another forming two different populations known as clades. That is why punctuated equilibrium is also known as cladogenesis.
Anagenesis vs 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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|Difference Between Allopatric And Sympatric Speciation|
|Darwin’s Contribution: The Theory of Evolution|
Frequently Asked Questions
What do you understand by anagenesis?
Anagenesis is a mechanism in which one species evolves into another by evolutionary changes within a lineage. The new species replaces the ancestral species making the ancestral species completely extinct.
Does anagenesis lead to speciation?
Anagenesis does not always lead to speciation. When speciation occurs, different lineages branch off and fail to interbreed. A specific group continues to be known as the original species.
What is phyletic evolution?
Phyletic evolution is a model of evolution which states that speciation is a slow, uniform and gradual process. This type of evolution leads to the transformation of a species into a completely new one.
What is cladogenesis?
Cladogenesis is the splitting of parent species into two different species forming a clade.
How is anagenesis different from cladogenesis?
In anagenesis, evolution takes places within a single lineage, and the parent species become extinct. Whereas in cladogenesis, an existing species diverges into two different species, and the parent species exists along with the newly formed species.