What is the Difference Between Apomixis and Parthenogenesis

The main difference between apomixis and parthenogenesis is that apomixis is the development of an embryo without undergoing fertilization whereas parthenogenesis is the development of an embryo directly from an egg cell without fusing to a sperm cell.

Apomixis and parthenogenesis are two methods of reproduction involved in the development of an embryo with no fertilization. They are methods of asexual reproduction. Apomixis replaces the seed of the plant with a plantlet or the flower with a bulbil. It does not essentially undergo meiosis. Parthenogenesis, on the other hand, is a process in which the egg cell directly develops into an embryo without undergoing fertilization with a sperm cell. It occurs in some plants, invertebrates including nematodes, some tardigrades, water fleas, some scorpions, aphids, some mites, some bees, some Phasmatodea and parasitic wasps, and some vertebrates including varieties of fish, amphibians, and reptiles. But, it rarely occurs in birds.  

Key Areas Covered

1. What is Apomixis
   • Definition, Reproduction, Importance
2. What is Parthenogenesis
   • Definition, Anatomy, Function
3. Similarities Between Apomixis and Parthenogenesis
   • Outline of Common Features
4. Difference Between Apomixis and Parthenogenesis
   • Comparison with Key Differences

Key Terms

Asexual Reproduction, Apomixis, Parthenogenesis

What is Apomixis

Apomixis refers to a method of asexual reproduction without undergoing fertilization. Therefore, it does not undergo meiosis. Here, a plantlet or bulbils replaces the seed. In addition, no gametes are involved in the process. Moreover, the daughter plant is genetically similar to the mother plant. In flowering plants, apomixis refers to agamospermy.

Figure 1: Apomixis

Furthermore, there are two methods of apomixis: obligate apomixis and facultative apomixis. In the former, some species only reproduce by apomixis while in the latter, some plants reproduce both sexually and asexually.

What is Parthenogenesis

Parthenogenesis is another type of asexual reproduction: a method of apomixis. It produces embryos only from the egg cell. Hence, there is no fertilization with sperm cells. In parthenogenesis, as the egg cell develops into an embryo, meiosis occurs in the process. And the egg cell is haploid with half the number of chromosomes as the diploid organism. Hence, parthenogenetic offspring contain haploid number of chromosomes. 

Figure 2: Parthenogenesis

In addition to plants, some invertebrate species such as nematodes, some tardigrades, water fleas, scorpions, aphids, some mites, some bees, some Phasmatodea, parasitic wasps, and some vertebrates including some fish, amphibians, reptiles undergo parthenogenesis. But rarely birds undergo parthenogenesis.

Similarities Between Apomixis and Parthenogenesis

• Apomixis and parthenogenesis are two methods of asexual reproduction in plants and some invertebrates.
• Moreover, both are methods of asexual reproduction.
• Hence, there are no fertilization gametes involved in these processes.

Difference Between Apomixis and Parthenogenesis

Definition

Apomixis refers to asexual reproduction in plants, in particular, agamospermy. Parthenogenesis, on the other hand, refers to reproduction from an ovum without fertilization, especially as a normal process in some invertebrates and lower plants.

Significance

Generally, apomixis produces genetically identical clones to the mother plant while parthenogenesis develops organisms from egg cells.

Occurs in

Apomixis occurs mainly in plants while parthenogenesis occurs in both plants and invertebrates.

Importance

In addition, apomixis is a method of asexual reproduction while parthenogenesis is a type of apomixis.

Conclusion

In brief, apomixis is a method of asexual reproduction in which an embryo develops without undergoing fertilization. Parthenogenesis, on the other hand, is a type of apomixis. But, it develops embryos from egg cells. Therefore, the main difference between apomixis and parthenogenesis is the method of developing embryos.

References:

1. Wikimedia Foundation. (2022, July 18). Apomixis. Wikipedia. Retrieved August 5, 2022.
2. Wikimedia Foundation. (2022, July 1). Parthenogenesis. Wikipedia. Retrieved August 5, 2022.

Image Courtesy:

1. ” Poa bulbosa, vegetative apomixis” By Nadiatalent- Own Work (CC BY-SA 3.0) via Commons Wikimedia
2. ” Cnemidophorus-ThreeSpecies” By Alistair J. Cullum – Own Work (Attribution) via Commons Wikimedia