What is a defining characteristic of a polyploid organism?

A polyploid organism is defined by having more than two complete sets of chromosomes. In most organisms, the standard condition is diploidy, which means they have two sets of chromosomes, one inherited from each parent. When an organism is polyploid, it can have triploidy (three sets), tetraploidy (four sets), or even higher levels of chromosome sets.

This characteristic is significant in genetics and evolution, especially in plants, where polyploidy can lead to greater genetic variation and potentially new species over time. Polyploid organisms often exhibit traits such as increased size or hybrid vigor, which can be advantageous for survival and reproduction.

The other options do not accurately describe polyploid organisms. A single set of chromosomes indicates a haploid state, while having exactly two complete sets defines a diploid organism. Incomplete sets of chromosomes would suggest a condition such as aneuploidy, where there is an abnormal number of chromosomes in a set. Therefore, the defining characteristic of polyploidy clearly aligns with having more than two complete sets of chromosomes.