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Question
Which of the following have an independent gametophyte generation and a dependent sporophyte generation?
Which of the following have an independent gametophyte generation and a dependent sporophyte generation?
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Solution
The correct option is A Mosses
- Alternation of generations is a term primarily used to describe the life cycle of plants (taken here to mean the Archaeplastida). A multicellular gametophyte, which is haploid with n chromosomes, alternates with a multicellular sporophyte, which is diploid with 2n chromosomes, made up of n pairs.
- A mature sporophyte produces spores by meiosis, a process that reduces the number of chromosomes to half, from 2n to n. Because meiosis is a key step in the alternation of generations, it is likely that meiosis has a fundamental adaptive function.
- The nature of this function is still unresolved, but the two main ideas are that meiosis is adaptive because it facilitates repair of DNA damages and/or that it generates genetic variation. In liverworts, mosses, and hornworts, the sporophyte is less well developed than the gametophyte and is largely dependent on it.
- Although moss and hornwort sporophytes can photosynthesize, they require additional photosynthate from the gametophyte to sustain growth and spore development and depend on it for the supply of water, mineral nutrients and nitrogen.
- In ferns, the gametophyte is a small flattened autotrophic prothallus on which the young sporophyte is briefly dependent for its nutrition.
- Alternation of generations is a term primarily used to describe the life cycle of plants (taken here to mean the Archaeplastida). A multicellular gametophyte, which is haploid with n chromosomes, alternates with a multicellular sporophyte, which is diploid with 2n chromosomes, made up of n pairs.
- A mature sporophyte produces spores by meiosis, a process that reduces the number of chromosomes to half, from 2n to n. Because meiosis is a key step in the alternation of generations, it is likely that meiosis has a fundamental adaptive function.
- The nature of this function is still unresolved, but the two main ideas are that meiosis is adaptive because it facilitates repair of DNA damages and/or that it generates genetic variation. In liverworts, mosses, and hornworts, the sporophyte is less well developed than the gametophyte and is largely dependent on it.
- Although moss and hornwort sporophytes can photosynthesize, they require additional photosynthate from the gametophyte to sustain growth and spore development and depend on it for the supply of water, mineral nutrients and nitrogen.
- In ferns, the gametophyte is a small flattened autotrophic prothallus on which the young sporophyte is briefly dependent for its nutrition.
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