Govt. Exams
Entrance Exams
In double fertilization, one sperm nucleus fuses with the egg nucleus to form diploid zygote (embryo), while the second sperm fuses with the two polar nuclei to form triploid endosperm.
Selaginella exhibits heterospory (producing two types of spores) and possesses a ligule (a small appendage), which are absent in Lycopodium.
Vascular tissue (xylem and phloem) was essential for water transport in terrestrial environments, enabling plants to grow upright and away from moisture sources.
The stamen is the microsporophyll of angiosperms that bears microsporangia (pollen sacs). Carpels are megasporophylls.
This represents a hermaphroditic flower with the potential for self-fertilization. Dichogamy prevents this by temporal separation, heterostyly by spatial separation.
Double fertilization is unique to angiosperms where one sperm nucleus fertilizes the egg (embryo) and another fertilizes the polar nuclei (endosperm), providing efficient nutrition for the developing embryo.
Apomixis is asexual reproduction in seeds where offspring are genetically identical to the parent, bypassing meiosis and fertilization.
Pteridophytes still require water as sperm are flagellated, but the prothallus provides a moist environment. True water independence came with seeds in gymnosperms.
The suspensor absorbs nutrients from the endosperm and pushes the developing embryo deeper into the embryo sac for better nourishment.
In ferns: diploid sporophyte (2n) → meiosis → haploid spores (n) → gametophyte (n) → fertilization → sporophyte (2n).
