Difference Between Fission and Fragmentation

The main difference between fission and fragmentation is that in fission, a parent cell splits into daughter cells, whereas, in fragmentation, a parent organism breaks into fragments, developing a new organism. Furthermore, fission occurs in unicellular organisms such as protists and bacteria while fragmentation occurs in multicellular organisms such as plants and Spirogyra.

Fission and fragmentation are two methods of asexual reproduction carried out by eukaryotes of lower organization and prokaryotes. The other type of asexual reproduction is budding, which is chiefly exhibited by yeast.

Key Areas Covered

1. What is Fission
     – Definition, Types, Examples
2. What is Fragmentation
     – Definition, Types, Examples
3. What are the Similarities Between Fission and Fragmentation
     – Outline of Common Features
4. What is the Difference Between Fission and Fragmentation
     – Comparison of Key Differences

Key Terms

Asexual Reproduction, Binary Fission, Fragmentation, Multiple Fission

What is Fission

Fission is a method of asexual reproduction in which a single parent cell divides into two or more daughter cells wherein each can then develop into a new organism. It mainly occurs in unicellular organisms. Based on the number of daughter cells forming, fission can be classified as binary fission and multiple fission.

Binary Fission

Binary fission is the main reproduction method in bacteria. It occurs through mitosis. This means it undergoes nuclear division to produce two daughter nuclei. After this, the parent cell divides into two by cytokinesis. The replication of organisms in eukaryotic cells also occurs through binary fission. Doubling time refers to the time taken by a parent cell to divide into two daughter cells. It is 15-20 minutes in E. coli.

Figure 1: Binary Fission in Bacteria

Multiple Fission

Multiple fission mainly occurs in protists such as sporozoans and algae. It can occur in bacteria as well. During multiple fission, the nucleus divides several times by amitosis and the subsequent cytokinesis results in several daughter cells that are genetically identical.

What is Fragmentation

Fragmentation is a method of asexual reproduction, which occurs in multicellular organisms. It is also called the clonal fragmentation as it can occur in colonial organisms as well. Fragmentation occurs in many plants, molds, lichens filamentous cyanobacteria and animals such as sea stars, sponges, annelids, and acoel flatworms. Fragmentation is one of the main methods of vegetative reproduction methods in plants by which they produce rhizomes, stolons, bulbils, adventitious plantlets, etc. It increases the members of that particular colony.

Figure 2: Sea Squirts Colonies

Fragmentation occurs in many colonial animals such as sponges and corals. It allows the regeneration in starfish. Paratomy and achitomy are the two mechanisms of fragmentation in animals. Both occur through the development of furrows at the zone of splitting. The splitting in paratomy occurs perpendicular to the antero-posterior axis while achitomy occurs at a particular point from which the missing tissues and organs regenerate.

Similarities Between Fission and Fragmentation

• Fission and fragmentation are two methods of asexual reproduction.
• Both methods are used by simple organisms.
• They produce daughter cells/organisms that are genetically identical to the parent cell/organism.

Difference Between Fission and Fragmentation

Definition

Fission refers to a method of reproduction by the spontaneous division of the parent cell into two or more parts, each of which grows into a complete daughter cell while fragmentation refers to a method of reproduction wherein a parent organism breaks into fragments, each capable of growing independently into a new organism.

Occurs in

Fission occurs in unicellular organisms such as amoeba, bacteria while fragmentation occurs in multicellular organisms such as plants, sea stars, planarians, molds, and Spirogyra.

Nuclear Division

Nuclear division occurs during fission while no nuclear division occurs during fragmentation.

Splitting

In fission, parent cell divides into daughter cells while in fragmentation, the parent organism divides into daughter organisms.

Daughter Cells/Organisms

Daughter cells are unicellular in fission while daughter organisms are mainly multicellular in fragmentation.

Deliberation

Fission occurs deliberately through mitosis while fragmentation may or may not be deliberate as it can occur through mechanical shearing as well.

Conclusion

Fission is a method of asexual reproduction in which a unicellular parent cell divides into two or more daughter cells. Fragmentation, on the other hand, is another asexual reproduction method in which the body of a multicellular organism divide producing a daughter organism. In fission, nuclear division takes place. The main difference between fission and fragmentation is the type of organisms that undergo each method of asexual reproduction.

Reference:

1. “Binary Fission – Definition, Steps and Examples.” Biology Dictionary, Biology Dictionary, 28 Apr. 2017, Available Here
2. “Fragmentation- Fragmentation in Animals and in Plants.” Byjus | The Learning App, Byjus Classes, 27 Feb. 2018, Available Here

Image Courtesy:

1. “Binary Fission 2” By Ecoddington14 – https://commons.wikimedia.org/wiki/File:Binary_Fission.png (CC BY-SA 3.0) via Commons Wikimedia 
2. “Sea Squirts Didemnum molle” By Silke Baron – originally posted to Flickr as Sea Squirts (CC BY 2.0) via Commons Wikimedia