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Class XI · First Year · Sindh / BIEK · Chapter 10

Kingdom Plantae.

Plants are multicellular eukaryotes that make their own food by photosynthesis. The kingdom tells the story of life moving onto land — from simple mosses up to the flowering plants that dominate the world today.

1 · What makes a plant

Members of Plantae are multicellular, eukaryotic autotrophs: they photosynthesise using chloroplasts. Their cells have cellulose cell walls and a large central vacuole. Adaptations for life on land include a waxy cuticle, stomata, and (in most) vascular tissue (xylem and phloem).

2 · The four main groups

The groups form a rough ladder of increasing adaptation to dry land:

GroupExamplesKey features
BryophytesMosses, liverwortsNon-vascular; small; no true roots (rhizoids); need water to reproduce
PteridophytesFernsVascular; true roots, stems, leaves; reproduce by spores
GymnospermsPine, conifersVascular; seeds exposed on cones (no flowers/fruit)
AngiospermsFlowering plantsVascular; flowers; seeds enclosed in fruit; most diverse

Angiosperms are split into monocots (one seed leaf, parallel veins — e.g. grasses, wheat) and dicots (two seed leaves, net veins — e.g. mango, beans).

3 · Alternation of generations

Plants have a life cycle that alternates between two forms:

Gametes fuse to make a diploid sporophyte; the sporophyte makes spores that grow into gametophytes — and so on. In mosses the gametophyte is dominant; in ferns and seed plants the sporophyte (the plant we usually see) is dominant.

Why seeds and flowers were game-changers

Seeds protect and feed the young plant and don't need water for fertilisation (pollen carries the male cells). Flowers and fruits attract animals to pollinate and to disperse seeds — which is why angiosperms became the most successful land plants.

In one minute