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Page No 45: - Chapter 3 Plant Kingdom class 11 ncert solutions Biology - SaraNextGen [2024]


Question 8:

Explain briefly the following terms with suitable examples:-

(i) protonema

(ii) antheridium

(iii) archegonium

(iv) diplontic

(v) sporophyll

(vi) isogamy

Answer:

(i) Protonema – It is the first stage in the life cycle of a moss, developing directly from the spore. It consists of creeping, green, branched, and often filamentous structures.

(ii) Antheridium – It is the male sex organ present in bryophytes and pteridophytes and is surrounded by a jacket of sterile cells. It encloses the sperm mother cells, which give rise to the male gametes.

(iii) Archegonium – It is the female sex organ present in bryophytes, pteridophytes, and gymnosperms. In bryophytes and pteridophytes, it generally has a swollen venter and a tubular neck, and contains the female gamete called the egg.

(iv) Diplontic – It is the term used for the life cycles of seed-bearing plants (gymnosperms and angiosperms). In these plants, the diploid sporophyte is dominant, photosynthetic, and independent. The gametophyte is represented by a single-celled (or a few-celled) structure.

(v) Sporophyll – In pteridophytes, the sporophytic plant body bears sporangia. These sporangia are subtended by leaf-like appendages known as sporophylls. In gymnosperms, microsporophylls and megasporophylls are found. These bear microspores and megaspores respectively.

(vi) Isogamy – It is a type of sexual reproduction involving the fusion of morphologically-similar gametes. This means that the gametes are of the same size, but perform different functions. This type of reproduction is commonly observed in Spirogyra.

Question 9:

Differentiate between the following:-

(i)red algae and brown algae

(ii) liverworts and moss

(iii) homosporous and heterosporous pteridophyte

(iv) syngamy and triple fusion

Answer:

(i) Red algae and brown algae

Red algae

Brown algae

1.

Red algae are grouped under the class Rhodophyceae.

1.

Brown algae are grouped under the class Phaeophyceae.

2.

They contain floridean starch as stored food.

2.

They contain mannitol or laminarin as stored food.

3.

They contain the photosynthetic pigments chlorophylls a and d, and phycoerythrin.

3.

They contain the photosynthetic pigments chlorophylls a and c, and fucoxanthin.

4.

Their cell walls are composed of cellulose, pectin, and phycocolloids.

4.

Their cell walls are composed of cellulose and algin.

5.

Flagella are absent

5.

Two flagella are present

 

Liverworts

Moss

1.

They have unicellular rhizoids.

1.

They have multicellular rhizoids.

2.

Scales are present very often

2.

Scales are absent

3.

They are generally thalloid, with dichotomous branching.

3.

They are foliage, with lateral branching.

4.

Gemma cups are present

4.

Gemma cups are absent

5.

Sporophyte has very little photosynthetic tissue

5.

Sporophyte has abundant photosynthetic tissue

(iii) Homosporous and heterosporous pteridophyte(ii) Liverworts and moss

Homosporous pteridophytes

Heterosporous pteridophytes

1.

They bear spores that are of the same type.

1.

They bear two kinds of spores – microspores and megaspores.

2.

They produce bisexual gametophytes.

2.

They produce unisexual gametophytes.

 

Syngamy

Triple fusion

1.

It is the process of fusion of the male gamete with the egg in an angiosperm.

1.

It is the process of fusion of the male gamete with the diploid secondary nucleus in an angiosperm.

2.

A diploid zygote is formed as a result of syngamy.

2.

A triploid primary endosperm is formed as a result of triple fusion.

Question 10:(iv) Syngamy and triple fusion

How would you distinguish monocots from dicots?

Answer:

Monocots and dicots can be differentiated through their morphological and anatomical characteristics.

Characteristic

Monocot

Dicot

Morphology

   

Roots

Fibrous roots

Tap roots

Venation

Generally parallel venation

Generally reticulate venation

Flowers

Trimerous flowers

Pentamerous flowers

Cotyledons in seeds

One

Two

Anatomy

   

No. of vascular bundles in stem

Numerous

Generally 2 – 6

Cambium

Absent

Present

Leaves

Isobilateral

Dorsiventral

Match the followings (column with column II)Question 11:

 

Column I

 

Column II

(a)

Chlamydomonas

(i)

Moss

(b)

Cycas

(ii)

Pteridophyte

(c)

Selaginella

(iii)

Algae

(d)

Sphagnum

(iv)

Gymnosperm

 

 

Column I

 

Column II

(a)

Chlamydomonas

(iii)

Algae

(b)

Cycas

(iv)

Gymnosperm

(c)

Selaginella

(ii)

Pteridophyte

(d)

Sphagnum

(i)

Moss

Question 12:Answer:

Describe the important characteristics of gymnosperms.

Answer:

Important features of gymnosperms:

1. The term gymnosperm refers to plants with naked seeds (gymnos – naked, sperma – seeds), i.e., the seeds of these plants are not enclosed in fruits.

2. The plant-body ranges from medium to tall trees and shrubs. The giant redwood tree Sequoia is one of the tallest trees in the world.

3. The root system consists of tap roots. The coralloid roots present in Cycas are associated with nitrogen-fixing cyanobacteria.

4. The stem can be branched (as in Pinus and Cedrus) or un-branched (as in Cycas).

5. The leaves can be simple (as in Pinus)or compound (pinnate in Cycas). The leaves are needle-like, with a thick cuticle and sunken stomata. These help in preventing water loss.

6. Gymnosperms are heterosporous. They bear two kinds of spores – microspores and megaspores.

7. Flowers are absent. The microsporophylls and megasporophylls are arranged to form compact male and female cones.

8. Pollination occurs mostly through wind and pollen grains reach the pollen chamber of the ovule through the micropyle.

9. The male and female gametophytes are dependent on the sporophyte.

10. The seeds contain haploid endosperms and remain uncovered.

Also Read : INTRODUCTION-Chapter-4-Animal-Kingdom-class-11-ncert-solutions-Biology

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