Meiosis and life cycle
Sexually reproducing beings have to have, at some point in their life cycle, meiosis for gametes to form. Depending on the moment of the biological cycle, the following are distinguished:
- Diplonte cycle. It is typical of animals, formed by diploid cells throughout the cycle, except in the gamete phase. The meiosis occurs in cells that originate gametes, single haploid cells of the cycle.
- Haplonte cycle. Typical of many protoctists and some fungi. The individual is haploid throughout the cycle, except in the zygote phase. The meiosis is immediately place after formation of the zygote, and leads to another generation haploid reproduces asexually: the gametophyte .
- Haplo-diplonte cycle. It is typical of plants. It consists of the combination of the two previous cycles, alternating a diploid generation (sporophyte) with another haploid (gametophyte). The diploid individual originates, by meiosis, haploid spores that, by mitosis, will give rise to a haploid individual. The haploid individual will produce gametes that, after uniting with another gamete at fertilization, will give rise to a diploid zygote that will give rise to a diploid individual.