Meiosis is important to eukaryotes, such as plants, animals and fungi, because it is the method by which they produce sex cells. The ability to produce sex cells, and therefore reproduce sexually, increases the genetic diversity of the population. This increased genetic diversity provides a greater pallet of mutations on which natural selection can act.
While most cells in eukaryotes divide through mitosis, sex cells, called gametes, divide by using a different process, termed meiosis. In mitosis, each daughter cell contains the full genetic compliment that was in the parent cell. By contrast, daughter cells that follow meiosis only have half of the genetic code of the parent cell. In other words, sperm and egg cells feature one-half of the DNA it takes to make an organism. When the male and female sex cells combine and initiate fertilization, the cells each contribute half of the DNA for the daughter organism.
Sexual reproduction is common among most macro-organisms, although some plants also use asexual methods of reproduction, such as vegetative propagation. Additionally, some animals, notably sponges, anemones and jellyfish, reproduce asexually by a process known as budding. In each of these examples, the offspring are genetically identical to the parent organisms.