Which of the following is NOT a source of genetic variation in sexually reproducing organisms?

Clonal reproduction is not a source of genetic variation in sexually reproducing organisms because it involves the production of offspring that are genetically identical to the parent. In clonal reproduction, organisms reproduce asexually, resulting in clones that carry the exact same genetic material as the parent.

In contrast, independent assortment, random fertilization, and crossing over are all mechanisms that enhance genetic diversity among offspring produced through sexual reproduction. Independent assortment refers to the random alignment and separation of chromosomes during meiosis, leading to different combinations of alleles. Random fertilization involves the chance combination of sperm and egg, resulting in unique genetic combinations. Crossing over occurs during meiosis when homologous chromosomes exchange genetic material, creating new allele combinations. Together, these processes ensure that sexually reproducing organisms exhibit significant genetic variation, which is crucial for evolution and adaptation.