Difference Between Monoecious and Dioecious

Main Difference – Monoecious vs Dioecious

Monoecious and dioecious are two ways of classifying organisms based on the presence of sex organs in the body. Flower is the sexual organ of angiosperms. Most angiosperms are hermaphrodites, consisting of bisexual flowers. Angiosperms bearing unisexual flowers can be either Monoecious or dioecious. Some invertebrates are monoecious. Most animals are dioecious, exhibiting sexual dimorphism. The main difference between monoecious and dioecious is that Monoecious organisms have both male and female reproductive organs whereas dioecious organisms consist of male and female organs in separate individuals.

1. What is Monoecious
      – Definition, Reproduction, Monoecious Organisms
2. What is Dioecious
      – Definition, Reproduction, Dioecious Organisms
3. What is the difference between Monoecious and Dioecious

What is Monoecious

Monoecious organisms contain both male and female reproductive organs in the same individual. Monoecy is more commonly found in conifers. It occurs less in angiosperms. Monoecy is found in invertebrates as well. Pine is a heterosporous conifer (corn-bearing seed plant), which carries both male and female sporophylls on the same sporophyte. Male corns are called staminate corns and produce microspores, which ultimately become pollen grains. Pollen grains are dispersed by the wind, landing on the ovulate corns. Ovulate corns are the female corns which produce ovules. Fertilization followed by the seed development of pines take about two years after the pollination.

Figure 1: Young male (yellow) and female (red) corns of European Larch

Angiosperms which are monoecious contain unisexual flowers of both sexes in the same plant. Corn is the most common example of monoecious angiosperms. Male flower of corn is developed at the top of the plant whereas the female flower is developed on the side of the plant. Tassle is the inflorescence of male flowers, which develops inside the plant and emerges out from the stem prior to its maturation. Male flowers only contain stamens rather than carpels. Female flowers emerge from the leaf nodes. They only contain carpels. The styles of the female flower are called silks. Male and female flowers of corn are shown in figure 2.

Figure 2: Male and female flowers of corn

Invertebrates like earthworms consist both male and female reproductive organs within the same organism. Hence, earthworms are considered as hermaphrodites. But, they are incapable of reproducing their own eggs due to the relative positions of genital apertures. Therefore, earthworms are protrandous since sperms are produced earlier than eggs, promoting cross fertilization.

What is Dioecious

Male and the female reproductive organs are found separate in dioecious organisms. In dioecious angiosperms, male and female flowers are found in separate flowers. Hence, dioecious plants bear sexual dimorphism. Dioecy is one of the adaptations in angiosperms to promote cross pollination (allogamy) while preventing self-pollination. Stamen is the male reproductive organ of the flower, consisting of an anther, which bears pollen grains and a filament, which supports the anther. Carpel is the male reproductive organ of the flower, consisting of an ovary, which bears the ovule, a stigma, in which the pollen grains are landed, and a style, which supports the stigma.  Plants that only contain stamens in flowers are called male plants. The corresponding female plants only contain carpels in their flowers. It is common in most woody plants as well as in heterotrophic species. The most common example of a dioecious plant is Cannabis.

Figure 3: Male flowers (A) and female seed-bearing parts (B) of Cannabis

Most animals are dioecious. Insects, spiders, fish, amphibians, reptilians, birds and mammals exhibit sexual dimorphism. Animal dioecy is called gonochory, where the separation of sexes in different individuals can be observed. Hydra is a dioecious animal in which an individual produces either sperms or eggs.

Figure 4: Male (left) and female (right) mandarin ducks

Difference Between Monoecious and Dioecious

Definition

Monoecious: Monoecious in organisms is the containment of both male and female reproductive organs in the same individual.

Dioecious: Male and female reproductive organs are found in separate dioecious organisms.

Gender

Monoecious: Monoecious are bisexual.

Dioecious: Dioecious are unisexual, which can be either male or a female organism.

In Angiosperms

Monoecious: Monoecious plants consists of male and female unisexual flowers in the same plant.

Dioecious: Dioecious plants consists of unisexual flowers where male and female flowers are on separate plants.

Gametes

Monoecious: Monoecious produce both male and female gametes by the same plant.

Dioecious: Dioecious produce male and female gametes in separate plants.

Parentage

Monoecious: Monoecious exhibit uniparental reproduction.

Dioecious: Dioecious exhibit biparental reproduction.

Self/Cross pollination

Monoecious: Monoecious plants are capable of using both self and cross pollination.

Dioecious: Dioecious plants only use cross pollination.

Isolation

Monoecious: Monoecious are capable of reproducing even when they are isolated.

Dioecious: Dioecious are incapable of reproducing when they are isolated.

Genetic Variation

Monoecious: Genetic variation is decreased in inbreeds of monoecious.

Dioecious: Variability, as well as heterozygosity, are increased in inbreeds of dioecious.

Examples of Plants

Monoecious: Squash, corn, walnut, oak and hazel are common monoecious plants.

Dioecious: Marijuana (Cannabis), Asparagus, Ginkgo biloba trees, Papaya, willow, holly, and poplar are dioecious plants.

Examples of Animals

Monoecious: Earthworms, slugs, jellyfish and planarians are examples of monoecious animals.

Dioecious: Mammals, birds, reptiles and insects are examples of dioecious animals.

Conclusion

Monoecy and dioecy are two types of reproductive morphologies. Other reproductive morphologies include hermaphroditism, gynomonoecy, and andromonecy. Monoecious organisms bear both male and female reproductive organs in the same individual, whereas each of the dioecious organism bears either male or female reproductive organs. This is the main difference between monoecious and dioecious. Most angiosperms are hermaphrodites, which consist of bisexual flowers. Unisexual flower-bearing angiosperms are either monoecious or dioecious. Conifers are monoecious plants. Some invertebrates like earthworms are monoecious as well. Animals and insects exhibit sexual polymorphism.

Reference:
1.Plant and Soil Sciences eLibrary:: Print Lesson. N.p., n.d. Web. 05 May 2017. <https://passel.unl.edu/pages/printinformationmodule.php?idinformationmodule=1087230040>.
2.Boundless. “Life Cycle of a Conifer – Boundless Open Textbook.” Boundless. Boundless, 26 May 2016. Web. 05 May 2017. <https://www.boundless.com/biology/textbooks/boundless-biology-textbook/seed-plants-26/gymnosperms-159/life-cycle-of-a-conifer-622-11843/>.
3.”Reproductive System of Earthworm.” Microbiology Notes. N.p., 25 Mar. 2016. Web. 05 May 2017. <http://www.microbiologynotes.com/reproductive-system-of-earthworm/>.

Image Courtesy:
1.”Fiore di larice” By Giallopolentacolor=”#ffd700″> – Own work (Public Domain) via Commons Wikimedia
2.”Zea mays – Köhler–s Medizinal-Pflanzen-283″ 由Franz Eugen Köhler, Köhler’s Medizinal-Pflanzen – List of Koehler Images (Public Domain) via Commons Wikimedia
3.”Cannabis sativa Koehler drawing” By Walther Otto Müller  (Public Domain) via Commons Wikimedia
4. “Pair of mandarin ducks” By © Francis C. Franklin (CC BY-SA 3.0) via Commons Wikimedia