Home Science Biology Life Cycle, Processes & Properties Alternate titles: diplohaplontic cycle, diplohaplontic life cycle, heterogenesis, metagenesis Show
alternation of generations, also called metagenesis or heterogenesis, in biology, the alternation of a sexual phase and an asexual phase in the life cycle of an organism. The two phases, or generations, are often
morphologically, and sometimes chromosomally, distinct. In algae, fungi, and plants, alternation of generations is common. It is not always easy to observe, however, since one or the other of the generations is often very small, even
microscopic. The sexual phase, called the gametophyte generation, produces gametes, or sex cells, and the asexual phase, or sporophyte generation, produces spores asexually. In terms of
chromosomes, the gametophyte is haploid (has a single set of chromosomes), and the sporophyte is diploid (has a double set). In bryophytes, such as mosses and liverworts, the gametophyte is the dominant
life phase, whereas in angiosperms and gymnosperms the sporophyte is dominant. The haploid phase is also dominant among fungi. Although some algae have determinate life cycle stages, many species
alternate between the sexual and asexual phases in response to environmental conditions. Among animals, many invertebrates have an alternation of sexual and asexual generations (e.g., protozoans, jellyfish, flatworms), but the alternation of haploid and diploid generations is unknown. This article was most recently revised and updated by Melissa Petruzzello. 7)Which of the following statementscorrectlydescribes the alternation of generation cycle of a fern?A) gametophyte-dominant (2n) life cycle where spores develop into photosynthetic sporophyte (n)B) gametophyte-dominant (n) life cycle where spores develop into photosynthetic sporophyte (2n)C) sporophyte-dominant (n) life cycle where 2 spores fuse to produce the zygote (2n)D) sporophyte-dominant (2n) life cycle where spores develop into photosynthetic gametophytes (n) 8)Which group is noted for the independence of gametophyte and sporophyte generations from eachother? Get answer to your question and much more 9)Within a gymnosperm megasporangium, what is thecorrectsequence in which the followingshould appear during development, assuming that fertilization occurs? Get answer to your question and much more 10)Which structure is common to both gymnosperms and angiosperms? Get answer to your question and much more Alternation of Generations Definition
Alternation of generations is common in plants, algae, and fungi. This can be compared to the sexual reproduction in animals where both haploid and diploid cells are found in every generation. Plants alternate between the diploid sporophyte and haploid gametophyte, and between asexual and sexual reproduction. Therefore, the life cycle of plants is known as alternation of generations. The ability of the plants to reproduce sexually and asexually helps them to adapt to different environments. The alternation of generations depends upon the type of the plant. In Bryophytes, the dominant generation is haploid and the gametophyte comprises the main plant. In tracheophytes, the dominant generation is diploid and the sporophyte comprises the main plant. The plants’ life cycle in one of the two generations is dominant over the other. The plants in the dominant generation grow larger and live longer. The plants in the non-dominant generations are small and hardly visible. On the contrary, the dominant generations are seen in the form of ferns, trees or other plants. The dominant generation in vascular plants is the sporophyte, while in the non-vascular plants is the gametophyte. Alternation of Generations – Life CycleAlternation of Generations The alternation of generations include the following stages:
Stages of Alternation of GenerationsFollowing are the two stages of alternation of generations: Sporophyte GenerationTwo 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. Also Read: Gymnosperms Gametophyte GenerationThis 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. Life Cycle Events in a Flowering PlantA flowering plant undergoes the following events during its life cycle:
Thus we see how a plant life cycle begins with a seed. The seed sprouts to form a seedling. The seedling gets converted into a new plant which forms new seeds and the cycle continues. Also Read: Sexual Reproduction in Plants For more information on the alternation of generations and other related topics, keep visiting BYJU’S website or download BYJU’S app for further reference. Related Links:- What correctly describes the alternation of generations in a plant life cycle?alternation of generations, also called metagenesis or heterogenesis, in biology, the alternation of a sexual phase and an asexual phase in the life cycle of an organism.
What is the alternation of generation life cycle?Alternation of generations is a type of life cycle found in terrestrial plants and some algae in which subsequent generations of individuals alternate between haploid and diploid organisms. This can be contrasted to sexual reproduction in animals, in which both haploid and diploid cells are found in every generation.
Which of the following correctly defines alternation of generations?1 Answer. Alternation of generation is defined as the alternation of multicellular diploid and haploid forms in the organism's life cycle.
Which of the following occurs during the alternation of generations in plants?Which of the following occurs during the alternation of generations in plants? Mitosis produces gametes.
|