Introduction
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.
FAQs on Speciation
1. What is speciation in simple terms?
Speciation is the evolutionary process by which new and distinct biological species arise. It occurs when a group within a species separates from other members of its species and develops its own unique characteristics, eventually becoming unable to interbreed with the original population.
2. What are the main types of speciation?
The primary types of speciation are distinguished by the geographical context in which they occur:
- Allopatric Speciation: New species form due to complete geographical isolation, such as being separated by a mountain range or a river.
- Peripatric Speciation: A small, isolated group at the edge of the main population's range breaks off and forms a new species.
- Parapatric Speciation: A new species forms from a population that is continuously distributed but experiences different environmental pressures across its range, leading to divergence.
- Sympatric Speciation: A new species evolves from a single ancestral species while inhabiting the same geographic region, often due to ecological or behavioural factors.
3. What is the key difference between allopatric and sympatric speciation?
The key difference lies in the presence or absence of a geographical barrier. Allopatric speciation requires a physical barrier that separates a population into two isolated groups, preventing gene flow. In contrast, sympatric speciation occurs without any physical barrier; new species arise within the same location due to other isolating mechanisms like polyploidy in plants or different mating preferences.
4. How do factors like genetic drift and natural selection lead to the formation of a new species?
Both are key mechanisms of evolution that drive speciation. Natural selection causes populations to adapt to different environments, favouring traits that increase survival and reproduction. Over time, these adaptations can make two populations very different. Genetic drift involves random changes in the gene frequencies of a population, which has a more significant effect in small, isolated populations. The accumulation of changes from both these factors can lead to a population becoming genetically distinct enough to be considered a new species.
5. Why is reproductive isolation considered crucial for speciation to be complete?
Reproductive isolation is the final and most critical step because it solidifies the separation between diverging populations. Even if populations have developed different traits due to natural selection or genetic drift, they are not considered separate species until they can no longer interbreed and produce fertile offspring. This inability to mix genes prevents the two groups from merging back into one, thus confirming the formation of a distinct new species.
6. Can speciation happen rapidly?
Generally, speciation is a very slow, gradual process that unfolds over thousands or millions of years. However, in some cases, particularly in plants through a mechanism called polyploidy (where an organism has more than two sets of chromosomes), speciation can occur much more rapidly, sometimes within a single generation. This is more common in plants than in animals.
7. What is a classic example of speciation, as studied in the CBSE syllabus?
A classic example of speciation is the case of Darwin's finches on the Galápagos Islands. Different finch populations became isolated on various islands with distinct food sources. Through natural selection, their beaks evolved different shapes and sizes to best exploit the available food (e.g., tough seeds, insects). This led to the formation of multiple distinct species from a common ancestor, a prime example of allopatric speciation and adaptive radiation.
8. What is the difference between speciation and evolution?
Evolution is the broad process of change in the heritable characteristics of biological populations over successive generations. Speciation is a specific outcome of evolution. While evolution can involve small-scale changes within a species (microevolution), speciation is the large-scale evolutionary event (macroevolution) that results in the formation of entirely new species.
