Class 11 Biology – Chapter 3: Kingdom Plantae (SSC Board)

Plants form a vital component of the biosphere. In Chapter 3 of the Class 11 SSC Board Biology textbook, we explore Kingdom Plantae, one of the five kingdoms of life as proposed by R.H. Whittaker. This chapter helps students understand the basis of classification of plants and the diversity that exists within this kingdom.

explore Class 11 SSC Board Biology Chapter 3 – Kingdom Plantae. Understand plant classification, key features, and types of plants including algae, bryophytes, pteridophytes, gymnosperms, and angiosperms.

1. Introduction to Kingdom Plantae

• Kingdom Plantae includes multicellular, eukaryotic, autotrophic organisms.
• Most plants are photosynthetic, containing the green pigment chlorophyll.
• They are non-motile and exhibit alternation of generations in their life cycle.
• Their cell walls are made of cellulose.

2. Basis of Classification in Plantae

The classification of plants is based on:

• Presence or absence of vascular tissues
• Body organization (differentiated into roots, stems, leaves)
• Mode of reproduction (spore formation, seed formation)
• Habitat (aquatic or terrestrial)
• Presence of seeds and flowers

3. Major Groups of Kingdom Plantae

Kingdom Plantae is classified into the following major divisions:

A. Algae (Division: Thallophyta)

• Aquatic, simple, autotrophic plants.
• Body is thalloid (not differentiated into root, stem, or leaves).
• Reproduce through vegetative, asexual, and sexual means.

Types of Algae:

• Green Algae (Chlorophyceae): e.g., Chlamydomonas, Ulothrix
• Brown Algae (Phaeophyceae): e.g., Fucus, Sargassum
• Red Algae (Rhodophyceae): e.g., Polysiphonia, Gracilaria

Algae are important for oxygen production and as sources of food, agar, and biofuels.

B. Bryophytes

• Called "amphibians of the plant kingdom" because they need water for reproduction.
• First land plants to evolve.
• Non-vascular, lack true roots, stems, and leaves but have similar structures.

Subdivisions:

• Liverworts (e.g., Riccia)
• Mosses (e.g., Funaria)

Life cycle shows alternation of generations, with dominant gametophyte generation.

C. Pteridophytes

• The first vascular plants with true roots, stems, and leaves.
• Reproduce by spores, not seeds.
• Found in moist, shady places.

Examples:

• Ferns, Marsilea, Selaginella

Have well-developed vascular tissue but do not produce flowers or seeds.

D. Gymnosperms

• Seed-producing plants but seeds are not enclosed in fruits (naked seeds).
• Mostly woody trees, adapted to dry conditions.
• Possess true vascular tissues, and dominant sporophyte generation.

Examples:

• Pinus, Cycas, Ginkgo

Produce cones instead of flowers. Male and female cones are separate.

E. Angiosperms

• Most advanced and diverse group.
• Also known as flowering plants.
• Seeds are enclosed in fruits.
• Well-developed vascular tissue, and reproduction occurs through flowers.

Classification:

• Monocots (e.g., Wheat, Rice): One seed leaf
• Dicots (e.g., Pea, Mango): Two seed leaves

Angiosperms show a wide range of adaptations and are the dominant plants in most ecosystems.

4. Life Cycle of Plants: Alternation of Generations

• Plants exhibit alternation of generations between a haploid gametophyte and a diploid sporophyte.
• In bryophytes, gametophyte is dominant.
• In pteridophytes, gymnosperms, and angiosperms, sporophyte is dominant.

5. Economic Importance of Plants

Plants are essential to life on Earth and are used for:

• Food: Cereals, vegetables, fruits
• Medicines: Herbal remedies, drugs like quinine
• Industrial Uses: Rubber, timber, paper
• Aesthetic & Cultural Value: Ornamentals, religious practices
• Environmental Role: Oxygen production, carbon dioxide absorption, soil conservation

Key Terms:

• Thallophyta: Algae, simple plants without roots/stems.
• Bryophytes: Non-vascular amphibian plants.
• Pteridophytes: First vascular cryptogams.
• Gymnosperms: Naked seed plants.
• Angiosperms: Flowering plants with fruits.

Kingdom Plantae displays an incredible diversity ranging from simple algae to highly evolved flowering plants. The chapter builds a clear understanding of the structural and functional differences between various plant groups.

• Algae are simple, aquatic plants.
• Bryophytes were the first land plants.
• Pteridophytes introduced vascular tissues.
• Gymnosperms brought in naked seeds.
• Angiosperms are the most evolved, with enclosed seeds and flowers.