Diversity of Living Organisms - Kingdom Plantae (Algae, Bryophytes, Pteridophytes, Gymnosperms, Angiosperms)

Kingdom Plantae includes eukaryotic, multicellular, autotrophic organisms characterized by the presence of rigid cell walls made of cellulose and photosynthetic pigments like Chlorophyll $a$ and $b$.

Algae: Thalloid plants, predominantly aquatic. Classified into Chlorophyceae (Green - storage as starch), Phaeophyceae (Brown - storage as $Laminarin$ or $Mannitol$), and Rhodophyceae (Red - storage as $Floridean$ starch).

Bryophytes: Known as the 'Amphibians of the Plant Kingdom'. They lack true vascular tissues and use rhizoids for anchorage. The dominant phase is the gametophyte ($n$).

Pteridophytes: The first terrestrial plants to possess vascular tissues ($Xylem$ and $Phloem$). The sporophyte ($2n$) is the dominant phase. They exhibit $Homospory$ or $Heterospory$ (e.g., Selaginella and Salvinia).

Gymnosperms: Plants with 'naked seeds' where ovules are not enclosed by an ovary wall. They feature specialized roots like $Mycorrhiza$ in Pinus and $Coralloid$ roots in Cycas.

Angiosperms: Flowering plants where seeds are enclosed in fruits. They exhibit a unique process called 'Double Fertilization' involving $Syngamy$ and $Triple Fusion$.

Alternation of Generations: The life cycle of plants involves a transition between a haploid gametophytic phase ($n$) and a diploid sporophytic phase ($2n$).