Plant Kingdom Neet Biology chapter Notes

 

🌱 Plant Kingdom – One Shot Notes

Systems of Classification

- Artificial System (Linnaeus)  

  - Based on superficial morphological characters (habit, color, leaf shape, etc.).  

  - Considered vegetative + sexual characters equally.  

  - Drawback: Closely related species separated; vegetative traits easily affected by environment.  

- Natural System (Bentham & Hooker)  

  - Based on natural affinities.  

  - Considered external + internal features (ultrastructure, anatomy, embryology, phytochemistry).  

- Phylogenetic System  

  - Based on evolutionary relationships.  

  - Organisms of same taxa assumed to share common ancestor.  

- Other Approaches  

  - Numerical Taxonomy – Characters coded numerically, analyzed by computers.  

  - Cytotaxonomy – Based on chromosome number, structure, behavior.  

  - Chemotaxonomy – Based on chemical constituents (DNA, RNA, proteins).  

Divisions of Plant Kingdom

1. Algae

- General Features  

  - Chlorophyll present, thalloid body (no true root, stem, leaf).  

  - Mostly aquatic (freshwater/marine), also on moist soil, stones, wood.  

  - Some form symbiosis (e.g., lichens).  

- Forms  

  - Colonial (Volvox), Filamentous (Ulothrix, Spirogyra), Marine (Kelps).  

- Reproduction  

  - Vegetative: Fragmentation.  

  - Asexual: Zoospores.  

  - Sexual: Isogamy, Anisogamy, Oogamy.  

- Economic Importance  

  - Fix ~50% of Earth’s CO₂, release O₂.  

  - Primary producers in aquatic ecosystems.  

  - Food: Laminaria, Sargassum, Porphyra.  

  - Hydrocolloids: Algin (brown algae), Carrageenan (red algae).  

  - Agar from Gelidium, Gracilaria (used in jellies, ice-cream).  

- Types  

  - Green Algae (Chlorophyceae) – Chlorophyll a & b, cell wall of cellulose + pectin, food stored as starch in pyrenoids.  

  - Brown Algae (Phaeophyceae) – Chlorophyll a & c, fucoxanthin pigment, food stored as laminarin & mannitol, cell wall with algin.  

  - Red Algae (Rhodophyceae) – Chlorophyll a & d, phycoerythrin pigment, food stored as floridean starch, found in deeper waters.  

2. Bryophytes

- Known as “Amphibians of Plant Kingdom” – live on soil but need water for sexual reproduction.  

- Found in moist, shaded habitats.  

- Important in ecological succession and preventing soil erosion.  

- Structure  

  - Thalloid body, attached by rhizoids (not true roots).  

  - Main plant body haploid (gametophyte).  

  - Sex organs multicellular:  

    - Male – Antheridium.  

    - Female – Archegonium (flask-shaped, contains single egg).  

  - Zygote develops into diploid sporophyte, attached to gametophyte.  

- Economic Importance  

  - Provide food for herbivores, birds.  

  - Sphagnum moss → peat (used as fuel, packaging).  

  - Colonizers of bare rocks along with lichens.  

- Groups  

  - Liverworts – e.g., Marchantia.  

    - Asexual reproduction via fragmentation or gemmae (multicellular buds in gemma cups).  

    - Sporophyte differentiated into foot, seta, capsule.  

  - Mosses – e.g., Funaria.  

    - Two stages: Protonema (filamentous, creeping) and leafy stage (upright axis with spirally arranged leaves).  

    - Sporophyte develops on gametophyte, produces spores by meiosis.