
Microevolution is the small, inherited changes that happen in a population of a species across generations. Antibiotic resistance among bacteria, pesticide resistance among insects and selective breeding of dogs are some of the common examples of microevolution.
Microevolution refers to the minute changes in the gene frequencies over a short period. They are driven by the fundamental evolutionary forces like mutation, migration, genetic drift and natural selection. It disrupts the genetic equilibrium, and if accumulated in a given population, can lay the foundation for speciation.
Changes associated with microevolution occur in a relatively shorter time. Since they often accumulate gradually, they may not be apparent in just one generation. Population genetics explains this using the Hardy–Weinberg equilibrium.
Microevolution in birds is exhibited by changes in size and bird colouration across generations.
Microevolution deals with the shift in allele frequencies in the gene pool of a particular population. The following evolutionary forces[c] contribute to this change:
Changes in DNA sequence are caused by replication errors, irradiation, mutagens, viruses, etc. If the mutation is advantageous, its frequency may increase over generations. Harmful mutations are generally selected against.
Individuals migrate between populations, causing shifts in allele frequencies and increasing genetic diversity.
Genetic drift is a random fluctuation of gene frequencies in small populations due to chance events such as bottleneck and founder effects.
Individuals with beneficial traits survive and reproduce more successfully, passing those traits to the next generation.
Drugs become ineffective over time as resistant individuals survive and reproduce, leading to resistant populations.
House sparrows introduced in 1852 evolved larger body sizes in colder regions due to directional natural selection.
Q1. Is speciation a microevolutionary process?
Speciation occurs when genetic divergence accumulates through microevolution. Once gene flow is restricted, new species evolve independently.
Q2. What does not contribute to microevolution?
Random mating, because it maintains constant allele frequencies.
Q3. Differentiate between microevolution and macroevolution with an example.
Microevolution refers to small genetic changes within a population, such as bacteria developing antibiotic resistance. Macroevolution refers to large-scale changes leading to new species, such as the evolution of birds from reptiles.
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