Diploid organisms contain
Diploid organisms maintain two complete chromosome sets, designated 2n, in somatic cells with homologous pairs one inherited from each parent. This state provides two allelic copies per locus, permitting dominance interactions, buffering deleterious recessives and enabling segregation. Diploidy is restored at fertilisation when haploid gametes fuse and reduced during meiosis maintaining constant chromosome number across generations. One set defines monoploid, three sets triploid and variable sets describe mixoploidy or aneuploidy, diploid condition dominates animal life cycles. This principle is routinely tested in NEET, CBSE 11-12, CUET, CSIR-NET, GATE and MSc Genetics examinations requiring clear conceptual distinction.
Ref: Pierce, Genetics, 7th ed., Chapter 2: Diploidy and Life Cycles