Haploidy and diploidy
Ploidy refers to the number of sets of chromosomes in a cell.
Haploid cells have one set of chromosomes. Gametes (sex cells) in sexually reproducing organisms are haploid.
Diploid cells have two sets of chromosomes (called homologous chromosomes). One set of chromosomes comes from each parents. In most animals, all somatic cells (body cells) are diploid.
Human sperm cells are haploid. A sperm cell contains a single copy of each chromosome (23 total). A human skin cell is diploid. It contains two copies (a pair) of each chromosome (46 total).
Some cells are polyploid and have more than two sets of chromosomes. Plants often have polyploid tissue. Polyploidy occurs if cells fail to divide properly during meiosis or mitosis.
Plants exhibit high tolerance for polyploidy. This means that polyploidy offspring can survive and reproduce, explaining the high incidence of polyploidy in these populations.