Anagenesis - Characteristics, Defination, Causes

Anagenesis is a type of evolutionary change where a single species gradually transforms into a new species over time without branching into different lineages. This continuous and gradual process involves the accumulation of genetic changes within a population. Anagenesis does not increase biodiversity but reflects transformation within a single line. This process contributes to our broader understanding of biological evolution, as it highlights how species can evolve steadily without forming new branches.

This Story also Contains

1. What Is Anagenesis?
2. Key Characteristics Of Anagenesis
3. Anagenesis Vs. Cladogenesis
4. Anagenesis Speciation
5. Cladogenesis Vs. Anagenesis In Speciation
6. Anagenesis And Cladogenesis In Biotechnology
7. MCQs on Anagenesis

In the context of evolutionary studies, anagenesis contrasts with cladogenesis, where new species branch off from a common ancestor. By studying anagenesis, scientists can trace evolutionary changes within a single lineage, often through fossil records and morphological comparisons. This concept also connects to Darwin's theory of natural selection, as selective pressures drive gradual changes in a species. Additionally, it helps explain long-term trends in evolution and supports various theories of evolution in biology.

What Is Anagenesis?

Anagenesis can also be termed "phyletic evolution" therefore, the gradual build-up of changes within a single lineage over time. This is speciation whereby one species evolves directly into another without the formation of new species. The new species supplants the old, yet no new species are produced. It stands in contrast to cladogenesis, in which one species divides into two or more species that are quite separate. Anagenesis simply states that in evolution, an ancestor species turns into a new species through the centuries due to chromosomal mutations, natural selection, and shifts in the environment.

Key Characteristics Of Anagenesis

Anagenesis involves gradual evolutionary changes within a single species over time. It results in the transformation of one species into a new form without branching. This type of evolution does not increase biodiversity. It shows adaptations to environmental changes. Some distinctive features of anagenesis are given below:

• Straight Line Evolution: While in the process of anagenesis, one species will turn into another with no division of species.

• Species Replacement: Species will eventually replace the original ancestral species since there is no original species anymore.

• No Increase in Diversity: The change does not make any increase in the number of species, but only one species changes into another.

• Slow Change: This process is normally slow and takes millions of years.

Anagenesis Vs. Cladogenesis

Anagenesis and cladogenesis are two patterns of evolutionary change. Anagenesis is a straight-line evolution without creating new species branches. In contrast, cladogenesis involves the splitting of one species into two or more distinct species, increasing biodiversity. Anagenesis and cladogenesis represent two different paths of evolutionary change.

Anagenesis Speciation

The other type of speciation is anagenesis, but this process does not contribute to species diversity. Instead, it is about how the process of one species gradually and constantly turns into another. Environmental pressures, mutations, and natural selection are the driving forces behind these changes. Eventually, the population is so transformed that it is regarded as a new species.

Example Of Anagenesis

A good example is the history of the modern horse, Equus, with its ancestor Eohippus. The species diversity over millions of years has evolved through size changes, limb structures, and dentition, without ever splitting into several species at any point in the evolutionary process.

Cladogenesis Vs. Anagenesis In Speciation

Both anagenesis and cladogenesis are significant parts of speciation but describe different results of an evolutionary process.

Anagenesis: One species changes into a new species. There is no increase in the number of species.

Cladogenesis: A parent species divides into two or more daughter species. There is an increase in biodiversity.

Anagenesis And Cladogenesis In Biotechnology

The study of biotechnology is associated with evolutionary studies that depend on the difference between anagenesis and cladogenesis. These concepts trace the lineage and evolutionary relationships used by the evolutionary biotechnologies involved in gene editing, species evolution, or genetic modification. Therefore, CRISPR and other biotechnology tools can trace back the evolutionary changes by comparing the genes of ancestors with modern species.

MCQs on Anagenesis

Q1. As evolution progresses, gene flow is eventually stopped between one population, and species behave as reproductively distinct from other populations of the species from which it diverged, termed as

1. Phyletic evolution

2. Anagenesis

3. Agenesis

4. Both (a) and (b)

Correct answer: 4) Both (a) and (b)

Explanation:

As evolution progresses, gene flow is eventually stopped between one population and species that behave as reproductively distinct from other populations of the species from which it diverged. This is also called Anagenesis.

Hence, the correct answer is Option 4) Both (a) and (b).

Q2. Q1. The formation of a new species through change in a single lineage is known as:

1. Anagenesis, or phyletic evolution

2. Cladogenesis, or divergent evolution

3. Convergent evolution

4. Allopatry

Correct answer: 1) Anagenesis, or phyletic evolution

Explanation:

Anagenesis refers to the evolutionary transformation of a single species into a new form without branching, meaning the original species is gradually replaced by the new one over time. It is also called phyletic evolution. Cladogenesis involves branching evolution where one species splits into two or more. Convergent evolution is when unrelated species develop similar traits. Allopatry refers to geographic isolation that may lead to speciation, not the process itself.
Hence, the correct answer is option 1) Anagenesis, or phyletic evolution.

Also Read:

• MCQs on Speciation & its types

• Evidence of Evolution

• Genetic Drift