Asexual reproduction is a form of reproduction that requires only one parent, with no exchange of genetic material and fertilization. A number of organisms use this method to perpetuate themselves. Some species are capable of both asexual and sexual reproduction, alternating methods depending on environmental factors. Most organisms that reproduce asexually are single celled, with the exception of plants, although some, like corals, may form clonal colonies that become quite large and are sometimes mistaken for a single organism.
There are a number of different ways in which an organism can reproduce asexually. One method is known to many gardeners: fragmentation. Some plants are capable of reproducing themselves with fragments that will eventually root and develop into clones of the parent plant. Fragmentation is used in the cloning and propagation of many plant species. Spore production is another method of reproduction that people may be familiar with, with some species producing spores that can mature into adult organisms.
Another method, commonly used by bacteria, is binary fission. In binary fission, a single celled organism replicates its DNA and then splits in two, creating a daughter cell that is identical to the parent. Budding is another technique that can also be seen in multicellular organisms. With budding, a daughter cell grows off the parent and eventually separates. Plants like strawberries use vegetative propagation, putting out rhizomes and other types of structures that eventually grow into new daughter plants that are identical to the parent. Yet another kind of asexual reproduction is parthenogenesis, sometimes referred to as “virgin birth,” in which an unfertilized egg can develop into a new organism.
Bacteria, fungi, protists, plants, and archaea have all been known to use asexual reproduction to reproduce. Among animals, it is relatively rare, however. There are a number of theories to explain this, with many focusing on the increased diversity available through sexual reproduction. When an organism reproduces asexually, the lack of new genetic material can make organisms vulnerable to disease and other problems, while in sexual reproduction, even if some organisms fail to survive, others will usually live on.
One advantage of this form of reproduction is that every member of a population is capable of reproducing, and that organisms can reproduce themselves very quickly. Bacteria, for example, are famous for their capability to multiply extremely quickly. It also requires less energy, and allows organisms to be more flexible in adverse environmental conditions, which can perpetuate the species as a whole.