what is alternation of generation in plants ? Explain the diplontic life cycle with suitable example .
Answers
The gametophyte is the dominant phase. The diplontic life cycle is commonly seen in gymnosperms and angiosperms with some variations. However, an Alga called Fucus also shows this kind of life cycle. In a diplontic life cycle, the diploid sporophyte is dominant, photosynthetic and is the independent phase of the plant.
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Answer:
Alternation of generations is a type of life cycle in which subsequent generations of plants alternate between diploid and haploid organisms.”
Explanation:
The alternation of generations include the following stages:
The diploid sporophyte has a structure called sporangium.
The sporangium undergoes meiosis and forms haploid spores.
The spore develops into a gametophyte which is haploid in nature.
The gametophyte has the reproductive organs which undergo mitosis to form haploid gametes.
The gametes fertilize to form a haploid zygote which matures into a mature sporophyte. This cycle keeps repeating.
Stages of Alternation of Generations
Following are the two stages of alternation of generations:
Sporophyte Generation
Two haploid gametes fuse together to form a diploid zygote. This results in a sporophyte.
The sporophyte is formed by multiple rounds of mitosis and is a multicellular organism. On reaching maturity, the sporophyte develops reproductive organs known as sporangia. This is one key point in the alternation of generations.
These sporangia are used to create haploid spores. These spores are released and carried away by air and water and when the conditions are favourable they develop into a gametophyte.
Gametophyte Generation
This is the next generation in the alternation of generations. The spore is newly formed and has half the DNA as the parent organism. This spore undergoes mitosis multiple times to form a gametophyte.
The gametophyte generation creates gametes. These gametes are produced by gametangia. These gametes are then transferred between plants or spread into the environment.
When a gamete encounters a gamete of the opposite sex, it fuses with it to form a zygote which eventually becomes a sporophyte.
This is the simplest version of alternation of generations. This is widely found in ferns.