Habit: Free living, attached.
Habitat: Aquatic, marine, tide pools, at the sea coast.
Structure: It is bright green in color. It is in the form of a sheet which is usually two celled thick.
Root like cells: These are present at the base of the plant. The cells are thread like and colorless. They anchor the plant to the rocks, bordering the tide pools.
Life Cycle of Ulva
Sporophyte: In Ulva we find different cells performing different functions i.e. there is division of labor. Ulva plant having 26 numbers of chromosomes is called sporophyte. Some of the cells grow and divide by meiosis and produce spores. The spores are tiny having four flagella and are motile. Each cell produces four spores. Spores are haploid having 13 chromosomes. Each spore grows and develops into a gametophyte.
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| Life Cycle of Ulva |
Gametophyte: Gametophytes are similar to the sporophytes in appearance but are haploid. Some cells of the gametophyte grow and divide by mitosis, forming gametes. They are tiny having two flagella and 13 chromosomes. Gametes unite and form the zygote. Zygote is diploid. It germinates into the diploid sporophyte.
Alternation of generations: An organism may have two phases in its life cycle. Having one phase as sporophyte and other phase as gametophyte. The sporophyte gives rise to a gametophyte and the gametophyte gives rise to a sporophyte. It is called alternation of generations.
Importance of alternation of generations: It is a mechanism for survival;
Generally different types of spores are produced by the process of meiosis. Each spore germinates into gametophyte.
The gametes unite to form the zygote and the zygote forms the sporophyte. Thus in each sporophyte there is mixing of characteristics. This genetic variation of the sporophyte helps the plant to survive in the changing environment.