[Biology Class Notes] on Speciation Pdf for Exam

Speciation refers to the process of how a new kind of animal or plant species is formed. It is an evolutionary process that leads to the formation of a new and distinct species that is reproductively isolated from another species. 

Speciation is also called ‘cladogenesis’, which means arising from a splitting event where the parent is split into two distinct species.

Types of Speciation

There are 5 types of speciation which include-

Allopatric Speciation- When a species is separated into two groups that are separate and isolated from one another, the type of speciation is known as allopatric speciation. This type of speciation occurs if any geographical changes occur. The geographical changes may include the formation of mountains by volcanoes, the formation of an island, human activities leading to habitat fragmentation, glaciers and rivers causing habitat separation and so on. 

An example of Allopatric Speciation is Darwin finches which led to the theory of evolution.

Peripatric Speciation- Peripatric Speciation occurs when a small group of individuals separate from a larger group and form new species. It is the mode of species formation in which speciation occurs from an isolated peripheral population. In this type of speciation genetic drift plays an important role.

Parapatric Speciation- When a part of an environment 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.

Sympatric Speciation- The type of speciation when there are no physical barriers to prevent any members of a species from mating with one another. All members are in close proximity to one another in this type of speciation. This type of speciation is common in herbivore insects when a new plant is introduced into a geographical range of species.

Artificial Speciation- The creation of new species by people is known as artificial speciation. An example of artificial speciation can be seen in fruit flies (Drosophilia Melanogaster). Artificial speciation is also known as artificial selection.

Factors Affecting Speciation

The factors that lead to speciation are as follows-

• Genetic Drift- The process describing random fluctuations in the frequencies of allele frequencies in populations is known as genetic drift. Genetic drift eventually leads to the formation of new species by causing a population of organisms to be genetically distinct from the original population.

• Natural Selection- The selection by which organisms are more likely to survive and reproduce is known as natural selection. Natural selection eventually leads to speciation.

• Geographic isolation- The mechanism of speciation in which populations of species are divided by geographic barriers. These geographic barriers may include rivers, water bodies and mountains.

• Mutation- Over a long period of time, the accumulation of many small genetic changes in a population occur, these changes are known as mutations. 

Reproductive Isolation- The inability of a species to breed with related species due to barriers or differences such as genetic, geographical, physiological, and behavioral.