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Sexual Vs. Non-sexual Reproduction

Most organisms reproduce sexually because there is a competitive advantage in producing offspring with genetic contributions from two individuals rather than one. The genetic recombination which occurs during meiosis and on fertilization allows new gene combinations to come together in the next generation. Organisms with new gene combinations are more variable and offer more options for selection pressures to select the best adaptations for the environmental conditions, for example making use of different food resources or being more resistant to pathogens.

Parthenogenetic animals receive all of their genes from one parent and therefore no new gene combinations are created. It may seem that this method of reproduction would put species that use it at a competitive disadvantage to sexually reproducing animals but it may be advantageous in some cases. To reproduce, a sexually reproducing organism must first find a mate and then combine gametes with this mate. This process requires a great deal of time and energy, and it may well result in no offspring. Parthenogenic organisms do not experience this cost of reproduction and therefore usually can reproduce sooner after birth and produce more offspring. Animals which live in environments that are hospitable for only a short time period are often parthenogenic because mating would take time that these organisms do not have; these animals need to produce large numbers of offspring to compensate for the low survival rate of the offspring. Minnows found in the southwestern United States living in rivers that dry to the point where only puddles remain, demonstrate parthenogenetic reproduction so eliminating the need for a suitable mate to be present in a given puddle. Another advantage of parthenogenetic reproduction is that most offspring are unlikely to survive the dry months, regardless of whether or not sexual recombination occurs. Therefore organisms which produce a greater quantity of offspring are more likely to have one survive to the next generation.

Parthenogenesis may also be advantageous in stable environments with ample food resources. These environments favor organisms with the ability to reproduce quickly allowing their offspring to consume the food resources before others do. This is the reason why certain cyclical parthenogens are so successful. For example, aphids reproduce parthenogenetically in the summer to exploit the abundant leaves which they feed upon. In the fall aphids produce fertilized eggs which may endure fluctuating environmental conditions when dormant during the winter or limited food supplies when they hatch in the spring.



Catton, Chris, and James Gray. Sex In Nature. New York: Facts on File, 1985.

Colinvaux, Paul. Ecology. New York: John Wiley & Sons, 1986.

Hughes, Roger. A Functional Biology of Clonal Animals. London: Chapman and Hall, 1989.

Suomalainen, Esko, Anssi Suara, and Juhani Lokki. Cytology and Evolution in Parthenogenesis. Boca Raton, FL: CRC Press, 1987.

Steven MacKenzie



—Seed development that occurs from an egg cell of a plant without it first being fertilized.


—Egg production without meiosis that results in the egg retaining a complete set of chromosomes.


—Egg production in which meiosis is altered so that the egg retains a complete set of chromosomes.


—he structures that carry genetic information in the form of DNA. Chromosomes are located within every cell and are responsible for directing the development and functioning of all the cells in the body.

Constant parthenogens

—Animals that always reproduce parthenogenetically.

Cyclical parthenogens

—Obligate parthenogens that alternate sexually reproductive generations with parthenogenic generations.

Facultative parthenogens

—Animals with the potential to reproduce parthenogenetically or sexually at all times.


—Union of male and female sex cells to form a diploid cell.


—Cell division which produces sex cells with only half the chromosome number as the parent.

Obligate parthenogens

—Animals in which individuals of at least one generation reproduce parthenogenetically.


—Process where genes from two individuals are contributed to an offspring.

Sex cells

—Cells which contribute genes to new offspring.

Additional topics

Science EncyclopediaScience & Philosophy: Overdamped to PeatParthenogenesis - Types Of Parthenogenic Organisms, Cellular Mechanisms, Sexual Vs. Non-sexual Reproduction