# Ploidy --- **Ploidy** is the number of complete sets of [[chromosome|chromosomes]] in any given. One or the other isn't necessarily better or worse—organisms just do how they do. The advantage of having only a single set of chromosomes is its simplicity. The advantage of having multiples of the same chromosome is the redundancy of having a "backup" copy of every gene—what we call [[allele|alleles]]. In general, the simpler the organism, the more likely it is haploid. **Haploid** or **(n)** organisms, like [[bacteria]], [[archaea]], and many [[algae]] and [[fungi]] have just one of each type of chromosome, therefore they have just one allele of each gene. **Diploid** or **(2n)** organisms like [[human|humans]] have two sets of chromosomes. The two "matching" chromosomes form one [[homologous pair]]. **Polyploid** or **(xn)** organisms have more than 2 homologs. This is seen a lot in organisms like salamanders and frogs (for some reason). %%line break below%% ___