Which term refers to organisms that possess three or more sets of chromosomes?

The term that refers to organisms possessing three or more sets of chromosomes is known as polyploid. Polyploidy occurs when a cell has more than two complete sets of chromosomes, which is a condition that can be found in many plants and some animal species. This genetic makeup can lead to increased size and vigor in plants, making them more resilient to environmental changes.

In contrast, diploidy refers to the condition of having two complete sets of chromosomes, which is typical for many organisms, including humans. Euploidy describes organisms that have a complete set of chromosomes, whether they be diploid, triploid, or even tetraploid, but it does not specifically focus on the presence of three or more sets. Aneuploidy, on the other hand, refers to the condition of having an abnormal number of chromosomes, which typically means missing or having extra chromosomes, rather than complete sets. Therefore, polyploid is the most appropriate term when discussing organisms with three or more sets of chromosomes.