Key Difference – Haplontic vs Diplontic Life Cycles
In the context of biology, a biological life cycle is a sequence of changes a particular organism undergoes through means of reproduction (sexual or asexual) which finally returns to the original starting phase. This procedure differs from one organism to the other. During sexual reproduction, the life cycle includes the change of ploidy; the alternation of haploid (n) and diploid (2n) stages. Meiosis occurs during the change over from a diploid stage to a haploid stage. With regards to change of ploidy, life cycles are of three types. They are, haplontic, diplontic and haplodiplontic. In a haplontic life cycle, the haploid stage is typically multicellular and results in the formation of a diploid (2n) cell, which is a zygote. The zygote undergoes meiosis, which results in the formation of haploid (n) cells. In a diplontic life cycle, the diploid stage is typically multicellular, and meiosis occurs during gamete formation which results in the production of haploid (n) gametes. During fertilization, the haploid (n) gametes fuse together in the formation of a diploid (2n) zygote, and it mitotically divides and produces a multicellular diploid (2n) organism. This is the key difference between haplontic and diplontic life cycles.
CONTENTS
1. Overview and Key Difference
2. What is a Haplontic Life Cycle
3. What is a Diplontic Life Cycle
4. Similarities Between Haplontic and Diplontic Life Cycles
5. Side by Side Comparison – Haplontic vs Diplontic Life Cycles in Tabular Form
6. Summary
What is a Haplontic Life Cycle?
Haplontic life cycle involves the formation of a haploid (n) single cell by the meiosis of a diploid (2n) zygote. This phenomenon could be explained with sporic meiosis – the process of formation of spores. In this process, the zygote mitotically divides and produces multicellular sporophyte which is diploid (2n). Within the sporophyte, meiotic cell division occurs and results in haploid (n) spores. The spores undergo mitosis and develop haploid (n) gametes together; This is referred to as the gametophyte. The gametophyte leads to the formation of gametes via mitosis.
Figure 01: Haplontic Life Cycle of Algae
In haplontic life cycle, the zygote is the only diploid (2n) stage, and mitosis occurs only in the haploid (n) phase. Since individual haploid (n) cells are formed by mitosis, this life cycle is referred to as haplontic life cycle. This includes the life cycles of many protozoa, all fungi, and some algae types.
What is a Diplontic Life Cycle?
During gamete formation, meiosis takes place in the formation of haploid (n) gametes. Haploid gametes are produced from individual cells of the diploid cells through meiosis. These haploid gametes do not undergo mitosis, and they do not develop into an organism. Instead, they fuse with gametes of the opposite sex and produce a diploid cell which is known as a zygote. The diploid (2n) zygote then develops mitotically into a diploid (2n) organism.
Figure 02: Diplontic Life Cycle
In the diplontic life cycle, the only haploid cells are the gametes. Meiosis only takes place in the diploid phase. Since the multicellular diploid individual is a diploid and the gamete undergoes meiosis, it is called a diplontic life cycle.
What are the Similarities Between Haplontic and Diplontic Life Cycles?
- Haplontic and diplontic life cycles are involved in the formation of gametes and development of a new organism.
- Meiosis and mitosis occur in both cycles.
What is the Difference Between Haplontic and Diplontic Life Cycles?
Haplontic vs Diplontic Life Cycles |
|
| In haplontic life cycle, mitosis occurs in the haploid (n) phase which is multicellular, and the diploid (2n) stage is the zygote which undergoes meiosis. | In diplontic life cycle, the diploid stage is typically multicellular, and meiosis occurs during gamete formation which results in the production of haploid (n) gametes and fuse to form a diploid (2n) zygote. |
| Mitosis | |
| Mitosis takes place in the haploid (n) phase in the haplontic life cycle. | Mitosis takes place only in the diploid (2n) phase of diplontic life cycle. |
| Examples | |
| All fungi, some varieties of algae and many protozoans have haplontic life cycles. | Animals and few brown algae have diplontic life cycle. |
Summary – Haplontic vs Diplontic Life Cycles
A biological life cycle is referred to as the series of events that take place within a particular organism through means of sexual or asexual reproduction which finally returns to the original starting phase. The life cycles differ with regards to different species. Alternation of generations takes place within a life cycle of a plant. In sexual reproduction, change of ploidy is of three types; haplontic, diplontic and haplodiplontic. In haplontic life cycle, mitosis occurs in the haploid (n) phase which is multicellular, and the diplod (2n) stage is the zygote which undergoes meiosis. In diplontic life cycle, the diploid stage is typically multicellular, and meiosis occurs during gamete formation which results in the production of haploid (n) gametes and fuse to form a diploid (2n) zygote. This is the difference between haplontic and diplontic life cycle.
Download PDF Version of Haplontic vs Diplontic Life Cycles
You can download PDF version of this article and use it for offline purposes as per citation note. Please download PDF version here Difference Between Haplontic and Diplontic Life Cycles.
References:
1.”Life cycles algae & plants.” Afzender. N.p., n.d. Web. Available here. 14 Aug. 2017.
2. Gilbert, Scott F. “Plant Life Cycles.” Developmental Biology. 6th edition.U.S. National Library of Medicine, 01 Jan. 1970. Web. Available here. 14 Aug. 2017.
Image Courtesy:
1. “Diploid English” By NuriaWrite – Own work (CC BY-SA 3.0) via Commons Wikimedia
“Haploid English” By NuriaWrite – Own work (CC BY-SA 3.0) via Commons Wikimedia