Chapter 5 — Plant Kingdom
Key Concepts Quick Recap
| Group | Key Features | Examples |
|---|
| Algae | No true roots/stems/leaves; aquatic; photosynthetic; thallus body | Spirogyra, Chlamydomonas, Fucus, Sargassum |
| Bryophytes | First land plants; no vascular tissue; gametophyte dominant; moist habitat | Marchantia (liverwort), Funaria (moss), Anthoceros (hornwort) |
| Pteridophytes | First vascular plants; no seeds; sporophyte dominant | Fern (Dryopteris), Selaginella, Equisetum |
| Gymnosperms | Vascular; seed-bearing; naked seeds; no flowers | Pinus, Cycas, Gnetum |
| Angiosperms | Vascular; seeds enclosed in fruit; flowers present; most dominant | Mango, Rice, Rose |
I. Choose the Best Answer (MCQs)
1. The plant group that lacks vascular tissue is: (a) Pteridophytes (b) Gymnosperms (c) Bryophytes (d) Angiosperms
Answer(c) Bryophytes Bryophytes (mosses, liverworts, hornworts) are the first land plants but lack true vascular tissue (xylem and phloem). They have simple conducting cells but no lignified xylem. Water and nutrients move by diffusion and osmosis — which is why they are restricted to moist habitats.
2. In which plant group does the gametophyte generation dominate? (a) Pteridophytes (b) Gymnosperms (c) Bryophytes (d) Angiosperms
Answer(c) Bryophytes In bryophytes, the dominant visible plant body is the gametophyte (n). The sporophyte (2n) is dependent on the gametophyte for nutrition. In all other groups (pteridophytes, gymnosperms, angiosperms), the sporophyte dominates.
3. Which of the following is a living fossil gymnosperm? (a) Pinus (b) Cycas (c) Gnetum (d) Ephedra
Answer(b) Cycas Cycas is called a "living fossil" — it has remained essentially unchanged for millions of years. It is a gymnosperm with large pinnately compound leaves resembling palms, but it bears cones (not flowers or fruit).
4. Seeds with two cotyledons belong to: (a) Monocots (b) Dicots (c) Gymnosperms (d) Pteridophytes
Answer(b) Dicots Dicotyledonous plants (dicots) have two cotyledons in their seeds. Examples: Mango, Bean, Pea, Sunflower. Monocots have one cotyledon. Examples: Rice, Wheat, Maize, Onion.
5. Rhizoids in bryophytes function as: (a) Photosynthetic organs (b) Reproductive organs (c) Absorbing organs (anchoring and water absorption) (d) Conducting tissue
Answer(c) Absorbing organs Rhizoids in bryophytes are unicellular (liverworts) or multicellular (mosses) thread-like structures that anchor the plant and absorb water and minerals. They are NOT true roots — they lack vascular tissue.
6. Which plant was the first to develop true vascular tissue? (a) Algae (b) Bryophytes (c) Pteridophytes (d) Gymnosperms
Answer(c) Pteridophytes Pteridophytes (ferns, Selaginella, Equisetum) are the first true vascular plants — they have xylem and phloem. This allowed them to grow taller and colonise drier habitats. However, they still require water for reproduction (motile sperm).
7. Heterospory means: (a) Production of one type of spore (b) Production of two types of spores (microspores and megaspores) (c) Spore production in gymnosperms only (d) Absence of spore production
Answer(b) Production of two types of spores Heterospory: producing microspores (small; → male gametophyte) and megaspores (large; → female gametophyte). First appeared in some pteridophytes (Selaginella). This is a precursor to the seed habit — in seed plants, the megaspore is retained within the parent plant.
II. Short Answer Questions
Q1. What is alternation of generations? Explain with a diagram.
Answer
Alternation of generations is the alternation between a haploid (n) gametophyte phase and a diploid (2n) sporophyte phase in the life cycle of plants.
Gametophyte (n):
- Haploid plant body.
- Produces gametes (egg and sperm) by mitosis.
- Gametes fuse (fertilisation) → zygote (2n).
Sporophyte (2n):
- Diploid plant body developed from zygote.
- Produces spores by meiosis (reduction division).
- Spores (n) germinate → gametophyte.
Spore (n) → [Mitosis] → Gametophyte (n) → Gametes (n)
↓ Fertilisation
Sporophyte (2n) ← [Zygote (2n)]
↓ Meiosis
Spores (n)
Trend across groups:
- Bryophytes: gametophyte dominant.
- Pteridophytes: sporophyte dominant; independent gametophyte.
- Gymnosperms/Angiosperms: sporophyte dominant; gametophyte reduced, retained within sporophyte.
Q2. Distinguish between gymnosperms and angiosperms.
Answer
| Feature | Gymnosperms | Angiosperms |
|---|
| Meaning | Naked seed (gymnos = naked) | Enclosed seed (angio = vessel) |
| Seeds | Naked — not enclosed in fruit | Enclosed in fruit (developed from ovary) |
| Flowers | Absent (cones/strobili) | Present |
| Pollination | Primarily wind (anemophily) | Wind, insects, water, birds (diverse) |
| Double fertilisation | Absent | Present |
| Endosperm | Formed before fertilisation (haploid) | Triploid (formed after triple fusion) |
| Leaves | Usually needle-like or scale-like (evergreen) | Broad, varied shapes (mostly deciduous) |
| Examples | Pinus, Cycas, Gnetum | Mango, Rose, Rice |
Q3. Describe the economic importance of algae.
Answer
Algae are economically important in many ways:
| Use | Example |
|---|
| Food | Porphyra, Sargassum (edible seaweeds); Chlorella (protein supplement) |
| Phycocolloids | Agar-agar from Gelidium/Gracilaria (microbiological media, food industry) |
| Carrageenan | Chondrus — used in dairy products, cosmetics |
| Biofuel | Microalgae (Chlorella) — potential source of biodiesel |
| Fertiliser | Blue-green algae (Cyanobacteria like Anabaena, Nostoc) fix nitrogen — used in paddy fields |
| Medicine | Alginic acid (from brown algae) — wound dressing; anti-ulcer drugs |
| Indicator | Algal blooms indicate water pollution |
III. Long Answer
Q1. Compare and contrast the features of the five major plant groups.
Answer
| Feature | Algae | Bryophytes | Pteridophytes | Gymnosperms | Angiosperms |
|---|
| Habitat | Aquatic | Moist/terrestrial | Moist/shaded | Temperate forests | All habitats |
| Body plan | Thallus | Thallus/leafy | Root/stem/leaf | Root/stem/leaf | Root/stem/leaf |
| Vascular tissue | Absent | Absent | Present | Present | Present |
| Seeds | Absent | Absent | Absent | Present (naked) | Present (enclosed) |
| Flowers | Absent | Absent | Absent | Absent | Present |
| Dominant generation | Gametophyte | Gametophyte | Sporophyte | Sporophyte | Sporophyte |
| Reproduction | Spores/fragmentation | Spores | Spores | Seeds | Seeds/fruit |
| Examples | Spirogyra | Funaria | Dryopteris | Pinus | Mango |
Common Mistakes
- Saying bryophytes are fully aquatic — they are first land plants but restricted to moist habitats.
- Confusing rhizoids (bryophytes) with true roots — rhizoids lack vascular tissue.
- Saying gymnosperms have flowers — they have cones/strobili.
- Forgetting that heterospory first appeared in pteridophytes (Selaginella), not gymnosperms.
Exam Checklist
- Gametophyte dominant: Bryophytes.
- First vascular plants: Pteridophytes.
- Heterospory: first appeared in pteridophytes (Selaginella).
- Gymnosperms: naked seeds, no fruit, wind pollination.
- Angiosperms: enclosed seeds, flowers, double fertilisation, triploid endosperm.
- Economic importance of algae: at least 4 uses.
