Difference Between Haplontic and Diplontic Life Cycle

The main difference between haplontic and diplontic life cycle is that the main form of the haplontic life cycle is haploid and its diploid zygote is formed for a short period of time whereas the main form of the diplontic life cycle is diploid, which produce gametes. Furthermore, most algae, most fungi, and lower plants have a haplontic life cycle while animals, higher plants have a diplontic life cycle. 

Haplontic and diplontic life cycle are multicellular life stages of organisms that undergo alternation of generations. 

Key Areas Covered 

1. What is Haplontic Life Cycle
     – Definition, Dominant Stage, Examples
2. What is Diplontic Life Cycle
     – Definition, Dominant Stages, Examples
3. What are the Similarities Between Haplontic and Diplontic Life Cycle
     – Outline of Common Features
4. What is the Difference Between Haplontic and Diplontic Life Cycle
     – Comparison of Key Differences

Key Terms 

Diploid, Diplontic Life Cycle, Haploid, Haplontic Life Cycle, Multicellular Organisms

What is Haplontic Life Cycle 

The haplontic life cycle is a type of life cycle with a dominant haploid stage. The zygote of the organisms with a haplontic life cycle undergoes meiosis immediately after karyogamy in a process called the zygotic meiosis. Hence, the organism ends up in a haploid stage. The mitotic cell division of these haploid cells allows the formation of a multicellular organism with a mass of haploid cells.

Figure 1: Haplontic Life Cycle

Two male and female gametes or cells fuse to form the zygote. Therefore, the only diploid cell formed during the haplontic life cycle is the zygote. 

What is Diplontic Life Cycle 

The diplontic life cycle is the type of life cycle with a dominant diploid life cycle. In the diplontic life cycle, the diploid zygote just divides through mitosis, forming a cell mass of diploid cells that form the multicellular organism. The cells of the diploid organism divide by meiosis to form the haploid gametes.

Figure 2: Diplontic Life Cycle

Fertilization of the gametes produces the next generation. Since gametes occur for a very short period of the life cycle, the dominant stage of the diplontic life cycle is the diploid stage. 

Similarities Between Haplontic and Diplontic Life Cycle 

• Haplontic and diplontic life cycles proceed through a haploid and diploid stage in an alternative manner. 
• Both occur in multicellular organisms with sexual reproduction. 
• They undergo mitosis and meiosis. 

Difference Between Haplontic and Diplontic Life Cycle 

Definition 

Haplontic life cycle refers to a life cycle in which the main form is haploid, with a diploid zygote being formed only briefly while diplontic life cycle refers to a life cycle in which the main form, except for the gametes, is diploid.  

Dominant Stage 

The dominant stage of the haplontic life cycle is the haploid stage while the dominant stage of the diplontic life cycle is the diploid stage. 

Significance 

The haplontic life cycle consists of a free-living gametophyte while the diplontic life cycle consists of a free-living sporophyte in plants. 

Minor Stage 

The minor stage of the haplontic life cycle is the zygote, which is diploid while the minor stage of the diplontic life cycle is the gamete, which is haploid. 

Zygote Undergoes 

The zygote of the haplontic life cycle undergoes meiosis while the zygote of the diplontic life cycle undergoes mitosis. 

Occurs in  

Most algae (Volvox, Spirogyra, Ulothrix, Chlamydomonas), most fungi, protists, and lower plants have a haplontic life cycle while animals and higher plants (gymnosperms and angiosperms) have a diplontic life cycle. 

Conclusion 

The haplontic life cycle consists of a dominant haploid stage in the life cycle while the diplontic life cycle consists of a dominant diploid life cycle. The main difference between haplontic and diplontic life cycle is the type of the dominant stage. 

Reference:

1. “Life Cycles in Plants and It Types (With Diagram).” Biology Discussion, 27 Aug. 2015, Available Here

Image Courtesy:

1. “Haploid English” By NuriaWrite – Own work (CC BY-SA 3.0) via Commons Wikimedia
2. “Diploid English” By NuriaWrite – Own work (CC BY-SA 3.0) via Commons Wikimedia