Practice question

Fertilization behavior in Gnetales demonstrates parallel to angiosperms: two non-flagellated sperm nuclei delivered via pollen tube, one syngamy with egg forming diploid zygote future embryo, second fuses typically with ventral canal nucleus creating additional diploid nucleus which aborts undergoing degeneration without forming persistent triploid nutritive tissue unlike angiosperms where triploid endosperm proliferates. Initial products therefore two diploid nuclei from double fertilization, contrasting triploid product in flowering plants. This homoplasious double fertilization illustrates convergent evolution delivering two male gametes simultaneously, but nutritional tissue formation mechanism not evolutionarily conserved between lineages, indicating independent origins of efficient provisioning strategies.