Explain briefly the following terms with suitable examples:
$(i)$ protonema
$(ii)$ antheridium
$(iii)$ archegonium
$(iv)$ diplontic
$(v)$ sporophyll
$(vi)$ isogamy

(N/A) $(i)$ Protonema: It is the first stage in the life cycle of a moss,developing directly from the spore. It consists of creeping,green,branched,and often filamentous structures.
$(ii)$ Antheridium: It is the male sex organ present in bryophytes and pteridophytes,surrounded by a jacket of sterile cells. It encloses the sperm mother cells,which give rise to the male gametes.
$(iii)$ Archegonium: It is the female sex organ present in bryophytes,pteridophytes,and gymnosperms. It typically has a swollen venter and a tubular neck,containing the female gamete (egg).
$(iv)$ Diplontic: This term describes the life cycle of seed-bearing plants (gymnosperms and angiosperms). In these plants,the diploid sporophyte is the dominant,photosynthetic,and independent phase,while the gametophyte is highly reduced.
$(v)$ Sporophyll: In pteridophytes,the sporophytic plant body bears sporangia,which are subtended by leaf-like appendages called sporophylls. In gymnosperms,these are differentiated into microsporophylls and megasporophylls.
$(vi)$ Isogamy: It is a type of sexual reproduction involving the fusion of morphologically similar gametes. These gametes are of the same size. This is commonly observed in $Spirogyra$.