Correct Option (b)
Mutationis the fundamental process that introduces new genetic variation into a population. It involves permanent, heritable changes in theDNA sequenceof an organism. These changes provide theraw material for evolution, leading to novel traits and alleles. The accumulation of beneficial or neutral mutations, often in conjunction with other evolutionary forces, can eventually result in reproductive isolation and the formation of a new species, a process known asspeciation.
Incorrect Options
Isolation (a): Isolation, whether geographic or reproductive, plays a crucial role in speciation by preventing gene flow between populations. This allows separated populations to diverge genetically. However, isolation itself does not generate new genetic variations; it merely facilitates the independent accumulation and differentiation of existing variations or new mutations within isolated groups.
Natural selection (c): Natural selection is a mechanism that acts on existing genetic variations within a population, favoring individuals with traits that enhance their survival and reproduction in a given environment. It drives adaptation and changes in allele frequencies over time, but it does not create the initial genetic variations upon which it operates.
Sexual reproduction (d): Sexual reproduction involves the recombination of existing genetic material from two parents, leading to new combinations of genes in offspring. This process significantly increases genetic diversity within a population. However, it does not introduce fundamentally new genetic information or novel traits; it shuffles the existing genetic pool. The ultimate source of entirely new genetic material is mutation.