Chapter 3: Plant Kingdom Short Questions | biology Class 11 CBSE

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Chapter 3: Plant Kingdom Short Questions | biology Class 11 CBSE | ByteNotes.in

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Question 1

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Define algae and state two habitats where they are found other than water.

Algae are chlorophyll-bearing, simple, thalloid, autotrophic, and largely aquatic organisms capable of photosynthesis.
They are found on moist stones and soils, extending beyond aquatic environments.
Some algae also occur in association with fungi forming lichens, and on animals such as the sloth bear.

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Question 2

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What are zoospores? State their significance in the life cycle of algae.

Zoospores are the most common type of asexual spores produced by algae during asexual reproduction.
They are flagellated (motile) spores capable of independent movement in water.
On germination, zoospores directly give rise to new algal plants, enabling rapid asexual propagation.

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Question 3

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Differentiate between isogamy and anisogamy with one example each.

Isogamy is the fusion of two gametes that are flagellated and similar in size, as seen in Ulothrix, or non-flagellated but similar in size, as in Spirogyra.
Anisogamy involves the fusion of two flagellated gametes that are dissimilar in size, as seen in species of Eudorina.
In isogamy, both gametes are morphologically identical, whereas in anisogamy, one gamete is distinctly larger than the other.

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Question 4

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What are pyrenoids? Mention their location and function.

Pyrenoids are storage bodies located within the chloroplasts of green algae (Chlorophyceae).
They contain protein in addition to starch, serving as the primary sites of starch synthesis and storage.
Their presence is a diagnostic feature of Chlorophyceae; some algae may alternatively store food as oil droplets.

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Question 5

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Name the pigments present in Phaeophyceae and explain how they determine the colour of brown algae.

Phaeophyceae possess chlorophyll a, chlorophyll c, carotenoids, and the xanthophyll pigment fucoxanthin.
The colour of brown algae varies from olive green to various shades of brown depending on the amount of fucoxanthin present.
Fucoxanthin masks the green colour of chlorophylls, causing the characteristic brownish appearance of the algae.

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Question 6

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State the food storage products and cell wall composition of red algae.

Red algae (Rhodophyceae) store food as floridean starch, which is structurally very similar to amylopectin and glycogen.
The cell wall of red algae is composed of cellulose, pectin, and polysulphate esters.
Red algae completely lack flagella, which distinguishes them from green and brown algae.

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Question 7

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Why are bryophytes called 'amphibians of the plant kingdom'?

Bryophytes can grow and survive on land (soil), similar to amphibians which can live on land.
However, they are dependent on water for the process of sexual reproduction, just as amphibians need water to breed.
The biflagellate antherozoids must swim through water to reach the archegonium for fertilisation to occur.

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Question 8

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Describe the structure and function of rhizoids in bryophytes.

Rhizoids are unicellular or multicellular thread-like structures that anchor the bryophyte plant body to the substratum.
They are root-like structures but differ from true roots in lacking vascular tissue and specialised absorptive cells.
In addition to anchorage, rhizoids may play a minor role in absorption of water and minerals from the substrate.

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Question 9

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What are gemmae? How do they help in asexual reproduction of liverworts?

Gemmae (singular: gemma) are green, multicellular, asexual buds formed by liverworts as a means of asexual reproduction.
They develop within small cup-like receptacles called gemma cups located on the thalli of liverworts such as Marchantia.
When mature, gemmae detach from the parent thallus and germinate under suitable conditions to form new independent individuals.

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Question 10

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Describe the two stages in the gametophyte of mosses.

The first stage is the protonema, which develops directly from a germinating spore; it is a creeping, green, branched, and frequently filamentous structure.
The second stage is the leafy stage, which develops from the secondary protonema as a lateral bud, consisting of upright slender axes bearing spirally arranged leaves.
The leafy stage bears the sex organs (antheridia and archegonia) at its apex and is attached to the soil by multicellular branched rhizoids.

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Question 11

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State two ecological roles of mosses in nature.

Mosses, along with lichens, are the first organisms to colonise bare rocks, making them ecologically important pioneer species.
They decompose rocks, making the substrate suitable for the growth of higher plants, and thus facilitate plant succession.
Since mosses form dense mats on soil, they reduce the impact of falling rain and help prevent soil erosion.

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Question 12

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What are sporophylls and strobili? Give one example of a plant that forms strobili.

Sporophylls are leaf-like appendages that subtend and bear the sporangia in pteridophytes and gymnosperms.
Strobili (singular: strobilus) are distinct, compact, cone-like structures formed when sporophylls aggregate around an axis.
Selaginella and Equisetum are examples of pteridophytes whose sporophylls form compact strobili or cones.

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Question 13

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Define prothallus and state the conditions it requires to grow.

The prothallus is the small, free-living, mostly photosynthetic, multicellular, thalloid gametophyte of pteridophytes that develops from spore germination.
It requires cool, damp, and shady places to grow due to its highly specific environmental requirements.
The prothallus bears the male sex organs (antheridia) and female sex organs (archegonia) responsible for sexual reproduction.

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Chapter 3: Plant Kingdom | Short Questions

Define algae and state two habitats where they are found other than water.

What are zoospores? State their significance in the life cycle of algae.

Differentiate between isogamy and anisogamy with one example each.

What are pyrenoids? Mention their location and function.

Name the pigments present in Phaeophyceae and explain how they determine the colour of brown algae.

State the food storage products and cell wall composition of red algae.

Why are bryophytes called 'amphibians of the plant kingdom'?

Describe the structure and function of rhizoids in bryophytes.

What are gemmae? How do they help in asexual reproduction of liverworts?

Describe the two stages in the gametophyte of mosses.

State two ecological roles of mosses in nature.

What are sporophylls and strobili? Give one example of a plant that forms strobili.

Define prothallus and state the conditions it requires to grow.

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