Speciation is the process through which new species come from existing ones, playing a crucial role in evolution. It occurs due to factors like geographic isolation, genetic variations, and natural selection. It drives biodiversity and explains the relationships between organisms. When these changes accumulate, they can lead to the formation of entirely new species. This process helps explain the vast biodiversity found on Earth and how organisms adapt to their specific environments. It is a fundamental concept in evolution.
A key factor in speciation is reproductive isolation, which prevents two populations from interbreeding. This isolation can be due to physical barriers, behavioral differences, or genetic incompatibility. Understanding speciation is essential in biology as it helps trace the evolutionary relationships between organisms and offers insight into how life continues to diversify.
Speciation can be defined as the process where some new distinct species are formed from already existing species. This occurs due to mechanisms that cause genetic differences as well as a lack of compatibility in reproduction. While, the process of evolution is defined as the change in the heritable characteristics of populations during successive generations influenced by factors like natural selection, mutation, gene flow, and genetic drift.
Combining concepts like speciation and evolution gives a clear perspective to the understanding of the differences in the forms of lives and their survival mechanisms in various ecosystems comprehensively identified as the ever-changing face of the Earth’s biodiversity.
Speciation can occur through different modes based on how populations become reproductively isolated. These modes help explain how one species splits into two or more over time. Understanding the types of speciation provides insight into how biodiversity increases through evolution. The types of speciation are described below-
Type of Speciation | Description |
Allopatric Speciation | Allopatric speciation takes place when physical barriers separate different populations of a species hence separating them genetically to warrant new species. |
Sympatric Speciation | Sympatric is the process which occurs with no geographical isolation so it occurs through factors such as polyploidy in plants or different habits due to behaviour in the same geographical area. |
Peripatric Speciation | It entails the splitting of a small population from a large one and often accompanies a process such as genetic drift and founder effect that explain how new species arise. |
Parapatric Speciation | Thus, parapatric speciation is a process when populations are somehow isolated but have some contact along certain lines. |
Evolution operates through various mechanisms such as natural selection, genetic drift, mutation, and gene flow. These processes bring about changes in the genetic makeup of populations over generations. Together, they drive the evolutionary journey of organisms. The mechanism is described below-
Natural selection explains that certain favourable characteristics are likely to be passed by to the progeny. They include, the formation of antibiotic resistance in bacteria and the evolution of Darwin’s finches feeding habits.
Genetic drift refers to the probability of changes in allele frequencies within a gene pool, which is effective in small populations. Genetic drift is illustrated by events such as the bottleneck effect which refers to the reduction of population size and the founder effect which involves the establishment of a new population by a few individuals.
Gene flow is the interchange or exchange of genes between populations and it leads to the introduction of certain factors that reduce the degree of dissimilarity between two populations.
Genetic mutations can be regarded as the primary source of variation, beneficial or deleterious, in the known hereditary material sequence.
Several factors influence how species evolve and new ones form such as geographical isolation, environmental changes, reproductive isolation, and genetic variations. These factors shape the direction of evolution. They are essential in studying the diversity and adaptation of life on Earth. The factors are described below:
Geographical isolation, for example by mountains, rivers and seas, isolates populations and does not allow them to interbreed. This leads to the formation of a new species.
Case Study: The isolation of finch populations by being on different islands yet all parts of the Galapagos led to Darwin’s Finches owing to their different adapted beaks to feed from separate trees.
Reproductive isolation ensures that different species do not mate with one another. Some of the prezygotic barriers include temporal, which refers to species that only mate at different seasons. While behavioural, mechanical and gametic refers to species whose reproductive behaviours, structural attributes and sperm respectively are incompatible. Postzygotic barriers consist of reduced hybrid viability; offspring die in the process of their development, or hybrid sterility, and offspring cannot reproduce.
One of the speciation mechanisms involves differences in ecological roles that populations occupy in a community. Example: Different species of cichlid fish are endemic to the African great lakes and these come in different forms and behaviours that are in line with their specific productive roles in the given environment.
Variations in chromosomes and polyploidy cause reproductive isolation and promote the process of speciation. Other reasons for isolation arise from studying genetic distances due to the accumulated mutations in the ability to reproduce with a different population successfully.
Environmental shocks, which include climate change and habitat destruction. It can introduce new selective forces in species population interaction and affect evolution. A classic example of environmental change is the peppered moth during the Industrial Revolution in England. As pollution darkened tree trunks, darker colored moths survived and lighter ones died.
Q1. Which speciation entails the appearance of a new species within the geographic range?
Sympatric speciation
Allopatric speciation
parapatric speciation
Peripatric speciation
Correct answer: 1) Sympatric speciation
Explanation:
Option (1)-Speciation happens when two populations of identical species live together without interbreeding is known as sympatric speciation. The development of new species occurs within the geographic range of the parental population.
Option (2)- Allopatric speciation occurs when geographical changes cause biological populations of the same species to become isolated from one another.
Option (3)- Two or more new species can arise from one common ancestor through a process known as parapatric speciation.
Hence, the correct answer is option 1) Sympatric speciation.
Q2. Which of the following statements is true about allopatric speciation?
I. Speciation isolates the population by geographic barriers
II. Physical isolation can emerge from animal and plant movements
III. Genetic divergence effects in reproductive compatibility
IV. It emerges only at the boundaries of the parent population
I and II
I and III
II and III
II and IV
Correct answer: 1) I and II
Explanation:
Statement I and II are true about allopatric speciation
Geographical barriers play a role in allopatric speciation because they physically separate populations. Physical isolation can also emerge from animal and plant movements. Genetic drift may cause unintentional variations in gene pools.
Statements III and IV are wrong.
Allopatric speciation does not take place at the boundaries of the parent population. Genetic divergence effects in reproductive incompatibility in allopatric speciation.
Hence, the correct answer is option 1) I and II.
Q3. Which hypothesis of speciation does not call on the reinforcing process?
Sympatric speciation
Allopatric speciation
Parapatric speciation
Peripatric speciation
Correct answer: 2) Allopatric speciation
Explanation:
The allopatric speciation theory does not necessitate the involvement of the reinforcing process.
Allopatric speciation transpires when distinct groups of a single species are geographically disconnected, which in turn induces genetic divergence due to isolation over a prolonged period. This divergence results in reproductive isolation, which is not contingent upon reinforcement. Reinforcement pertains to the evolutionary process that enhances reproductive barriers when two previously isolated populations encounter secondary contact, typically observed in sympatric or parapatric speciation scenarios where proximity may lead to hybridization.
In contrast, allopatric speciation's emphasis lies in the separation and divergence of genetic traits without dependence on reinforcement mechanisms. The primary focus is the natural divergence that arises from geographic isolation, which is sufficient for the formation of new species.
Hence, the correct answer is option 2) Allopatric speciation.
Also Read:
Speciation is the evolutionary process by which new biological species arise from existing ones due to genetic isolation and divergence.
Allopatric speciation occurs when populations are geographically separated, leading to the formation of new species.
Sympatric speciation happens without geographic separation, often due to genetic changes. Example: polyploidy in plants like wheat.
The bottleneck effect is a sharp reduction in population size due to environmental events, reducing genetic variation.
The founder effect occurs when a small group from a population starts a new colony, carrying only a limited genetic variation.
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