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The haplontic life cycle refers to a type of life cycle with a dominant haploid stage. Haplontic is a kind of life cycle in Biology where the zygote takes the lead, meaning, zygotes are the only diploid cell. It divides itself mitotically in order to give rise to a brand new plant. After undergoing the process of meiosis, the zygote forms haploid spores. These are dominant and each spore divides further to form a gametophyte.
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Key Terms: Haplontic life cycle example, Haplontic and diplontic life cycle, Haplontic life cycle meaning, Diplontic life cycle, Haplodiplontic life cycle
Haplontic Life Cycle
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The Haplontic Life Cycle refers to a cycle of organisms that is dominated by the haploid gametophyte. This is usually seen in microorganisms brimming around us. These may be algae, for example, volvox, spirogyra, ulothrix, and chlamydomonas.
Haplontic Life Cycle Process
 Haplontic Life Cycle |
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What is a Life Cycle?
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Life Cycle refers to the biological changes an organism goes through in its life span. The term can be more precisely described as the changes happening to an organism from its birth till its next generation, which is known as its life cycle. These changes or transitions may vary completely from each other.
Life cycle transitions may be in the form of sexual reproduction or asexual reproduction. It basically means a single individual, while growing up into its development stage, divides or splits up into two individuals.
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Types of Life Cycle
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The life cycle of plants undergoing sexual production observes the haplontic and diplontic cycles alternatively. Both are crucial and complementary to each other.
However, with reference to the ploidy, there are 3 important cycles:
- Haplontic life cycle: Here, there are 23 chromosomes and it is denoted by n. In this cycle, meiosis is of zygotic nature. The haploid is dominant and multicellular. The diploid is a single independent cell.
- Diplontic life cycle: Gametic mitosis is observed here. The diploid sporophyte is in charge here. This cycle is generally observed in Angiosperms and Gymnosperms. There are 46 chromosomes present here. It is denoted as 2n.
- Haplodiplontic life cycle: This phase is multicellular and is seen in bryophytes. It is also known as the diplobiontic cycle.
Difference between Haploid Life Cycle and Diploid Life Cycle
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The haplontic and diplontic life cycles are equally important and essential in the life of plants. Both happen simultaneously and maintain the balance during their development stage.
Difference between Haploid Life Cycle and Diploid Life Cycle
Both of them have very interesting aspects as well as points of difference. Let us get a better understanding of that from the table below.
| Haploid life cycle | Diploid life cycle |
|---|---|
| This life cycle is basically very common in microorganisms like most of algae. These are Ulothrix, Chlamydomonas, Volvox, and Spirogyra. This life cycle can also be found in some fungi, and protists. | A diploid life cycle is typically observed in angiosperms, gymnosperms, and also some algae. These are Fucus, Cladophora, etc. |
| Here, the zygote undergoes meiosis. | In this type of cycle, the zygote undergoes mitosis. |
| The embryo takes form in the haploid life cycle, only when the zygote undergoes the process of meiosis. | The diploid life cycle observes the diploid sporophyte as an independent body which acts as the dominant one. |
| In this cycle, the haploid dominates the process. | The diploid dominates the stage here. |
| Here, the haploid divides mitotically to give rise to new plants. | In order to be able to give rise to a new plant, the zygote will split or divide mitotically. |
| Zygospores are contained inside the walls or membrane of a single cell. These zygospores are of the zygote origin and help identify the sporophyte stage. | The gametes formed here are of haploid nature. These are called sporophytes and are clearly definite. |
| A free-living gametophyte is present here. | Free-living sporophytes are present here. |
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Things to Remember
- In plants, both haploid cells and diploid cells are present and they hugely contribute to deciding the types of the life cycle.
- There are three kinds of life cycles: Haplontic life cycle, Diplontic life cycle, and Haplodiplontic life cycle.
- Haplontic life cycle refers to a cycle that is mostly found in algae like Spirogyra, Volvox, and Chlamydomonas. These can also be seen in most of the fungi family and in protists.
- When the zygote undergoes the process of meiosis, haploid spores are formed. These spores become gametophytes by splitting up. The gametophytes are free and independent and are crucial for photosynthesis.
- The most interesting aspect about both the life cycles is the minor stage, or when they are new and growing. The minor stage of a haplontic cycle is a zygote. This zygote in turn happens to be diploid. This is very contrasting to the diploid cycle.
- In the diploid cycle, the minor stage is a gamete, and this gamete is of haploid nature.
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Previous Year Questions
- The lack of fruit formation in gymnosperm is due to … [JIPMER 2003]
- Which part of Ephedra yields ephedrine? … [MU OET 2011]
- The seeds of Cycas are … [JIPMER 1999]
- Turpentine oil is obtained from … [JIPMER 2003]
- A gymnospermic leaf carries 16 chromosomes … [NEET 1996]
- Correct position of floral parts over thalamus in mustard plant … [NEET 2020]
- Gymnosperms are also called soft wood spermatophytes … [NEET 2012]
- In gymnosperms, the pollen chamber represents … [NEET 2007]
- In Pinus/Cycas/gymnosperms, the endosperm … [NEET 1998]
- Strobili or cones are found in … [NEET 2020]
- Which of the following statements is incorrect about gymnosperms … [NEET 2020]
- Which of the following gymnosperms is a bushy trailing shrub … [KEAM]
- A plant having seeds but lacking flowers and fruits belongs to… [NEET 1992]
- Which one of the following is not common between Funaria and Selaginella...[NEET 1992]
- The plant group that produces spores and embryo but lacks vascular tissues and seeds is...[NEET 1992]
- A plant in which sporophytic generation is represented by zygote is...[NEET 1992]
- Select the correct statement... [NEET 2016]
- Protonema occurs in the life cycle of... [NEET 1990]
- Moss peristome takes part in... [NEET 1990]
- The pyrenoids are made up of... [NEET 1995]
Sample Questions
Ques: Where can we see the haplontic life cycle taking place? (3 marks)
Ans: The haplontic life cycle can be most commonly seen in microorganisms like algae, fungi, protists, and even some of the lower plants. Volvox, Spirogyra, and Chlamydomonas are very good examples of algae. In addition to this, colonial algae and even filamentous algae like red, green, and brown algae exhibit the structure of the haplontic life cycle. It should be noted that the algae are those without the dikaryotic phase, whereas the fungi are of the dikaryotic phase in this case.
Ques: What are the different life cycles present? (2 marks)
Ans: Organisms concerning sexual reproduction experience three life cycles. These are
- Haplontic life cycle
- Diplontic life cycle, and
- Haplodiplontic life cycle
Ques: What do you mean by a haploid cell? (3 marks)
Ans: A haploid cell refers to a single set of chromosomes. The number of chromosomes present in a haploid cell is denoted by the letter n. In humans, this number happens to be 23. Gametes are the best example of haploid cells, and they are formed as a result of meiosis. Haploid also denotes the male and female reproductive cells, which are the sperms and eggs respectively. Apart from algae and fungi, male ants and bees also have haploid cells present in them.
Ques: How do haplontic and diplontic life cycles differ from each other? (3 marks)
Ans: In a haplontic life cycle, a haploid is a striking element, whereas, in a diplontic life cycle, a diploid dominates. In the former’s case, gametophytes are present. They are independent, free-living, and need no host’s support. Whereas, in the latter free-living sporophytes are there. The haplontic life cycle is mostly observed in fungi, algae, and protists, whereas diplontic is found in gymnosperms and angiosperms.
Ques: What are the similarities between the haplontic life cycle and the diplontic life cycle? (2 marks)
Ans: Both of the life cycles take place in multicellular organisms with sexual reproduction. Another point of similarity is that both the life cycle stages observe a haplontic cycle and diplontic cycle alternatively. Also, it should be remembered that both life cycles go through mitosis and meiosis.
Ques: Why are the cells called haploid? (2 marks)
Ans: Every chromosome exists in the form of a pair. It has company. These are called diploids. However, sperms and egg cells have 23 chromosomes present in number, or we could say exactly half the number of diploid cells. This is because diploid cells are 46 in number. Therefore, the name haploid is given to these cells.
Ques: Define life cycle. What are the types of the life cycle? (5 marks)
Ans: The different biological changes an organism goes through in its life span are known as the life cycle. The term can be more precisely described as the changes happening to an organism from its birth till its next generation, which is known as the life cycle.
The three types of the life cycle are as follows:
- Haplontic life cycle- Here, there are 23 chromosomes and it is denoted by n. In this cycle, meiosis is of zygotic nature. The haploid is dominant and multicellular. The diploid is a single independent cell.
- Diplontic life cycle- Gametic mitosis is observed here. The diploid sporophyte is in charge here. This cycle is generally observed in angiosperms and gymnosperms. There are 46 chromosomes present here. It is denoted as 2n.
- Haplodiplontic life cycle- This phase is multicellular and is seen in bryophytes. It is also known as the diplobiontic cycle.
Ques: How does the haplontic life cycle take place? (4 marks)
Ans: The zygote is formed when in meiosis, the embryo takes life. This zygote undergoes a division and splits itself or divides mitotically into haploid cells. These cells further go through mitosis so as to be able to form multicellular haploid organisms. The sporophytes are represented by the zygotes. This zygote, or zygospores, is contained within the walls of a single cell. The gametophyte is a free-living body, independent, and can be formed from every spore given the right conditions. It is concerned with the function of carrying out photosynthesis.
Ques. What is Gametophyte? (1 mark)
Ans. Gametophyte can be described as the gamete producing haploid phase typically found in the plant life cycle.
Ques. What is a Sporophyte? (1 mark)
Ans. A Sporophyte can be defined as the spore-producing diploid phase typically found in the plant life cycle.
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