Speciation And Evolution - Factors Affecting

Table of Contents

• Introduction
• Speciation Definition
• What is Speciation?
• Speciation Types
• Factors Affecting Speciation

Evolution is the successive modification of inherited traits over a huge span of time, usually over generations. The theory of evolution was first proposed by an English biologist named Charles Darwin. In 1859, he mentioned evolution in his book ‘The Origin of Species’.

Charles Darwin noted that living organisms change their physical and anatomical structure over a long period of time for better adaptations to the changing environment. The change is by natural process and those organisms which do not adjust to it, find it difficult to survive. This put forward the concept of natural selection and Darwin called it ‘Survival of the fittest’. Speciation is an evolutionary process that resulted in natural selection.

Also Read: Anagenesis

Let us learn more about the concept of speciation and the factors affecting speciation.

“Speciation is the process of formation of new species from existing populations.”

A species is a group of organisms with similar characteristics and can interbreed to give fertile offspring. Speciation is an evolutionary process of the formation of new and distinct species. The species evolve by genetic modification. The new species are reproductively isolated from the previous species, i.e. the new species cannot mate with the old species.

Also Read: Concept of Species

Allopatric Speciation

Allopatric speciation is the type of speciation caused by geographical isolation. In this, the population is separated by a physical barrier.

Parapatric Speciation

This is a type of allopatric speciation in which the species are not formed by any physical barrier. Instead, they are beside each other. This occurs by an extreme change in the habitat. Though the individuals in these areas can interbreed, they develop different characteristics and lifestyles.

Peripatric Speciation

This is a type of allopatric speciation in which new species are formed from an isolated peripheral population. In this, the populations are prevented from exchanging genes and therefore it is difficult to distinguish between them.

Sympatric Speciation

It refers to the evolution of new species from the surviving ancestral species in which both the species continue to live in the same geographical region.

 There are several factors that lead to speciation. Two of them are:

Geographical Isolation

Due to some geographical changes, few members of a species get isolated from other members. Later, this isolated group grows in a different land and eventually evolves as a new species with new adaptations according to its environment. Natural selection and genetic drift have a major role to play in this.

Also Read: Natural Selection

Let’s understand this concept with an example.

Suppose earlier there was a species of flies living on land A. Some of them fed on dead animals. Evidently, there was a flood that washed off the dead animals and the flies feeding on them. Consequently, a few groups of flies get isolated from the other members to another land B. The species on land A and land B are too far to unite. Moreover, the environmental conditions in land B are different from those on mainland A. The groups of flies which now live inland B start to adapt themselves according to their environmental conditions. Gradually, the individual’s structure and functions alter to give rise to a new species. This is speciation.

The new species are different from the flies in mainland A as well as from the flies who got introduced to land B by the flood. Even if this new species was reintroduced to mainland A, they would not mate with those flies. New species start to mate amongst themselves. Thus, a population of new species arrives.

Hybridization

Hybridization is an artificial method of developing a new species. In animal husbandry, two parents from different species are mated to form a third species. Hybridization has numerous impacts on the process of speciation.

There are many hybrid animals, which have been crossed between the same species and the genus. Below is the list of a few successfully crossed hybrid animals:

• Zebroid- It is a hybrid cross between a male zebra (Equus quagga) and a female donkey (Equus asinus) or with any other female members of the horse family.
• Liger – It is a hybrid cross between a male lion (Panthera leo) and a tigress (Panthera tigris).

Also Read: Animal Husbandry

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