8. The Asian mongoose and the American skunk evolved independently of each other,
but show similar structures and features, for e.g., ability to spray their attacker with musk.
The similarities between the two organisms are most likely the result of:
a. genetic drift
b. divergent evolution
c. allopatric speciation
d. convergent evolution
The similarities between the Asian mongoose and the American skunk are best explained by convergent evolution. The correct answer is: d. convergent evolution.
Understanding the question
The Asian mongoose and the American skunk belong to different evolutionary lineages but show similar traits such as the ability to spray musk as a defense. This situation describes unrelated or distantly related species evolving similar adaptations because they face similar ecological pressures and occupy similar niches. This pattern is the hallmark of convergent evolution, where similar functions arise independently in different lineages.
Option (d) Convergent evolution – correct
Convergent evolution occurs when species from different ancestral lineages independently evolve similar traits or features because they experience similar environmental pressures or ecological roles. These traits are called analogous structures, meaning they have similar function but evolved separately rather than from a recent common ancestor. The musk-spraying mechanism in both the Asian mongoose and the American skunk is an analogous defense adaptation, evolved independently in different carnivoran lineages responding to similar predator–prey pressures.
Option (a) Genetic drift – why it is incorrect
Genetic drift is a random change in allele frequencies in a population, especially noticeable in small populations, due to chance events rather than adaptive natural selection. It does not systematically produce similar complex adaptive traits in unrelated species, because its effects are random and not driven by similar ecological demands. Therefore, genetic drift cannot explain the parallel evolution of a sophisticated defense like musk-spraying in both mongoose and skunk.
Option (b) Divergent evolution – why it is incorrect
Divergent evolution occurs when closely related species share a common ancestor but gradually accumulate differences, often because they adapt to different environments or niches. This process produces homologous structures, which share an evolutionary origin but may differ in function or appearance, such as vertebrate forelimbs evolving into wings, flippers, and arms. In the mongoose–skunk example, the emphasis is on similar traits in unrelated lineages, which is the opposite pattern of divergence.
Option (c) Allopatric speciation – why it is incorrect
Allopatric speciation refers to the formation of new species when populations of a single species become geographically isolated and diverge genetically over time. While allopatric speciation explains how one species can split into two or more species due to geographic barriers, it does not specifically account for unrelated lineages independently evolving similar traits. The question focuses on similarity between different lineages, not on the splitting of one species into two, so allopatric speciation is not the right concept here.
SEO-optimized introduction including keyphrase
The Asian mongoose and American skunk convergent evolution example is a powerful illustration of how unrelated animals can independently develop similar defense strategies when exposed to comparable environmental challenges. When both species evolved the ability to spray musk at predators, they did not inherit this trait from a recent common ancestor; instead, natural selection shaped similar solutions in separate lineages. Understanding why convergent evolution, and not genetic drift, divergent evolution, or allopatric speciation, explains this similarity is essential for mastering core concepts in evolutionary biology and exam questions on analogous structures.
