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Speciation & Its Types | Biology Class 12 - NEET PDF Download

Speciation

Formation of one or more new species from an existing species is called speciation. Speciation are of 2 types.

A. DIVERGENT SPECIATION : Origin of one or more new species from an ancestor species is called divergent speciation.

In this type of speciation ancestor speciation also continuous to exist with new species.

In this type of speciation no. of species are increased.

Divergent speciation are of two types – 

(1)  Allopatric Speciation : When a species split into two or more geographically isolated population and these population finally form a new species.

This mode of speciation is called allopatric speciation and these speciation are known as allopartic species.

Ex. : Finches of Darwin are example of Allopatric speciation.

(2) Sympatric species : In this type of speciation a sub population becomes reproductively isolated from its parental population.

Sympatric speciation is the formation of species without geographical isolation and these speciation are known as sympatric species.

B. Transformation speciation : In this type of speciation an ancestor species change into a new speciation with time. In this process no. of species is not increased.

Transformation speciation are of two types –

(1)  Phyletic Evolution : When an ancestor speciation changed in to a new species by gradual change in thousand of years.

e.g. Eohippus → Mesohippus → Merychippus → Pliohippus → equus

(2)  Quantum Species : In this process suddenly major changes appears in ancestor species and ancestor species immediately changed into new speciation. No. connective links are present in this type of speciation. It is caused by major mutation.

Special point : 

Micro evolution : - Micro evolution is the occurrence of small-scale changes in gene frequencies in a population, over a few generations.

It occurs at or below the species level. It often cause the formation of new subspecies.

These changes may be due to several process-Natural selection, gene flow. mutation, recombination, genetic drift etc.

eg. Formation of clines.     

Macro evolution : - Macro evolution is the evolution, which results in the production of new adaptive types through a process of population fragmentation and genetic divergence.

It is the occurrence of large-scale changes in gene frequencies in a population, over a geological time period (consisting of lots of micro evolution).

Macro evolution operates above the species level and results in the establishment of new genera, families and order.

The changes in the organization occurs due to accumulation of large mutation (macro mutation).

The divergent evolution of different reptilian group from initial reptile ancestor is example of macro evolution.

Mega evolution : - The origin and evolution of new types of biological organization as a result of general adaptation  from its predecessor  resulting in the formation of new classes, phylum.

Mega evolutionary changes are rare and have occurred only a few times in the evolutionary history of living beings.

Ex. Origin of Amphibia from fishes, origin of reptiles from amphibian, origin of bird and mammal from reptile.

Anagenesis : - It is the evolution of species involving a change in gene frequency in an entire population. It is also known as phyletic change. Anagenesis may also be referred to as phyletic species or gradual species.

Cladogenesis : - It is an evolutionary splitting event in which each branch and it's smaller branches form a ' clade' an evolutionary mechanism and a process of adaptive evolution that leads to the development of a greater variety of sister organism.

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FAQs on Speciation & Its Types - Biology Class 12 - NEET

1. What is speciation?
Ans. Speciation refers to the process by which new species evolve from existing ones. It occurs when populations of a species become reproductively isolated and diverge genetically over time.
2. What are the types of speciation?
Ans. There are two main types of speciation: allopatric speciation and sympatric speciation. Allopatric speciation occurs when populations of a species become geographically isolated, leading to genetic divergence. Sympatric speciation, on the other hand, occurs when new species arise within the same geographical area without any physical barriers.
3. How does allopatric speciation occur?
Ans. Allopatric speciation occurs when a physical barrier, such as a mountain range or a body of water, separates a population into two or more isolated groups. This isolation prevents gene flow between the populations, allowing genetic differences to accumulate over time. Eventually, the populations become reproductively isolated and evolve into separate species.
4. What are the mechanisms of sympatric speciation?
Ans. Sympatric speciation can occur through several mechanisms, including polyploidy, disruptive selection, and sexual selection. Polyploidy refers to the duplication of entire sets of chromosomes, resulting in individuals with multiple sets of chromosomes. Disruptive selection occurs when different phenotypes are favored in different parts of the same habitat, leading to reproductive isolation. Sexual selection can also drive sympatric speciation by favoring individuals with specific traits as mates.
5. How does speciation contribute to biodiversity?
Ans. Speciation is a fundamental process that drives the evolution and diversity of life on Earth. Through speciation, new species emerge, increasing the total number of species in an ecosystem or on the planet. This increased biodiversity is essential for ecosystem stability, as it provides a variety of ecological niches and promotes resilience in the face of environmental changes. Additionally, speciation allows for the formation of unique adaptations and specialized roles within ecosystems, further enriching the overall biodiversity.
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