What defines polyploidy?

Polyploidy refers to the condition in which a cell or organism has more than two complete sets of chromosomes. In humans, the normal diploid state consists of two sets of chromosomes (one from each parent), but in polyploid organisms, this can include triploidy (three sets), tetraploidy (four sets), and so forth. Polyploidy is common in plants and can lead to increased genetic diversity, larger cell size, and greater adaptability to various environmental conditions. This condition plays a significant role in the evolution of species and can be a mechanism for speciation.

The other options do not accurately describe polyploidy: having one extra chromosome defines aneuploidy, normal chromosome count indicates a diploid state, and having fewer than two sets of chromosomes describes haploidy. Thus, only the definition of having more than two sets of chromosomes aligns with the concept of polyploidy, which is essential in understanding certain biological processes and plant evolution.