Final answer:
Polyploidy is extremely rare in mammals and more commonly found in some other animal groups and especially in plants, where it leads to larger and more robust species.
Step-by-step explanation:
False, polyploidy is not most common in mammals; rather, it is an extremely rare occurrence. Polyploid animals, which have more than two sets of chromosomes, can be found in only a few classes such as flatworms, crustaceans, amphibians, fish, and lizards. These animals are usually sterile, as their meiosis does not produce viable gametes due to the production of mostly aneuploid daughter cells. In contrast, polyploidy is quite prevalent in the plant kingdom, where it often results in larger and more robust plants compared to their euploid counterparts.
Polyploidy is a condition in which a cell or organism has an extra set or sets of chromosomes. While polyploidy occurs rarely in mammals, it is very common in the plant kingdom. Polyploid plants tend to be larger and more robust than their diploid counterparts.