What went wrong when the king rode under the arch?

It was too low and knocked off his crown

How does the chain of blame unfold in the poem?

Each accused person blames another, ending with the king's own changes

What is the basis of classification of algae?

Algae are classified on the basis of their major photosynthetic pigments and the type of stored food, giving Chlorophyceae, Phaeophyceae and Rhodophyceae.

Why are bryophytes called amphibians of the plant kingdom?

Because they can live in soil but still depend on water for sexual reproduction, since the antherozoids must swim to the archegonium.

What is heterospory and why is it significant?

Heterospory is the production of two kinds of spores (micro and mega); it is significant because retention of the megaspore and development of the embryo within it is a precursor to the seed habit.

Why are gymnosperms called naked-seeded plants?

Because their ovules are not enclosed by an ovary wall and the resulting seeds remain exposed.

Name three groups of plants that bear archegonia.

Bryophytes, pteridophytes and gymnosperms all bear archegonia.

Both gymnosperms and angiosperms bear seeds; why are they classified separately?

In gymnosperms seeds are naked, whereas in angiosperms the ovules develop inside an ovary and the seeds are enclosed within fruits.

Distinguish between red algae and brown algae.

Red algae (Rhodophyceae) owe their colour to r-phycoerythrin and store floridean starch, while brown algae (Phaeophyceae) owe their colour to fucoxanthin and store laminarin or mannitol.

What is the dominant phase in the life cycle of a moss and of a fern?

In a moss the dominant phase is the gametophyte, while in a fern (pteridophyte) the dominant phase is the sporophyte.

Give two economic uses of algae.

Algae such as Porphyra and Laminaria are used as food, and red and brown algae yield commercial hydrocolloids such as agar, algin and carrageen.

Into which two classes are angiosperms divided?

Angiosperms are divided into dicotyledons and monocotyledons.

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Chapter 3: Plant Kingdom — Class 11 Biology

Biology · 19 chapters

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Chapter 3: Plant Kingdom

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Algae are classified into three classes on the basis of their:

Summary

This chapter classifies Kingdom Plantae into algae, bryophytes, pteridophytes, gymnosperms and angiosperms, and explains how classification has moved from artificial systems based on a few characters to natural and phylogenetic systems. Algae are simple, chlorophyll-bearing, largely aquatic thalloid autotrophs that reproduce by fragmentation, spores and gametes (isogamous, anisogamous or oogamous); they are divided by pigment and stored food into Chlorophyceae (green), Phaeophyceae (brown) and Rhodophyceae (red). Bryophytes, the amphibians of the plant kingdom, depend on water for sexual reproduction; their dominant plant body is a haploid gametophyte, and they include liverworts and mosses. Pteridophytes are the first plants with true vascular tissue; their dominant phase is the sporophyte, and many are homosporous while some, like Selaginella, are heterosporous, foreshadowing the seed habit. Gymnosperms bear naked seeds not enclosed in an ovary and are heterosporous, with male and female cones and reduced gametophytes retained on the sporophyte. Angiosperms produce flowers, enclose seeds in fruits, and are divided into dicotyledons and monocotyledons. A recurring theme is alternation of generations between haploid gametophyte and diploid sporophyte phases, whose relative dominance shifts across these groups.

Algae: Chlorophyceae, Phaeophyceae, RhodophyceaeBryophytes: liverworts and mossesPteridophytes and the seed habitGymnosperms and naked seedsAngiosperms: dicots and monocotsAlternation of generations

Key terms

Algae

Simple, chlorophyll-bearing, thalloid, largely aquatic autotrophic plants.

Bryophytes

Amphibians of the plant kingdom whose dominant plant body is a haploid gametophyte; includes liverworts and mosses.

Pteridophytes

The first vascular plants whose dominant phase is the sporophyte with true roots, stem and leaves.

Gymnosperms

Plants whose ovules and seeds are naked, not enclosed within an ovary wall.

Alternation of generations

The life-cycle pattern in plants where a haploid gametophyte phase alternates with a diploid sporophyte phase.

Heterospory

The production of two kinds of spores, microspores and megaspores, as in Selaginella and gymnosperms.

Important questions

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Algae

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Simple, chlorophyll-bearing, thalloid, largely aquatic autotrophic plants.

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