CBSE - Plant Kingdom

Algae are classified into three main classes – Chlorophyceae, Phaeophyceae, and Rhodophyceae. These divisions are based on the following factors:

(a) Major photosynthetic pigments present

(b) Form of stored food

(c) Cell wall composition

(d) Number of flagella and position of insertion

Class I – Chlorophyceae

Common name – Green algae

Major pigments – Chlorophylls a and b

Stored food – Starch

Cell wall composition – Cellulose

Flagella number and position – 2-8; equal and apical

Class II – Phaeophyceae

Common name– Brown algae

Major pigments – Chlorophylls a and c, and fucoxanthin

Stored food – Mannitol and laminarin

Cell wall composition – Cellulose and algin

Flagella number and position – 2; unequal and lateral

Class III­ – Rhodophyceae

Common name – Red algae

Major pigments – Chlorophylls a and d, and phycoerythrin

Stored food –­ Floridean starch

Cell wall – Cellulose, pectin, and polysulphate esters

Flagella number – Absent

Liverwort – In liverworts, the main plant-body is haploid (gametophytic). It bears the male and female sex organs which produce gametes. These gametes fuse to form a zygote. The zygote develops on the gametophytic plant-body to form a sporophyte. The sporophyte is differentiated into the foot, seta, and capsule. Many haploid spores are produced as a result of the reduction division taking place inside the capsule.

Moss – In mosses, the primary protonema (developed in the first stage) develops into the secondary protonema. Both these stages are haploid or gametophytic. The secondary protonema bears the sex organs which produce gametes. These gametes fuse to form a zygote. The zygote develops into a sporophyte. Many spores are formed as a result of the reduction division taking place in the capsule of this sporophyte.

Fern – In ferns, the main plant-body is sporophytic. Its leaves are known as sporophylls and these bear the sporangia. Reduction division takes place in these sporangia, thereby producing many spores.

Gymnosperm – In gymnosperms, the main plant-body is sporophytic. They bear two types of leaves – microsporophylls and megasporophylls. Reduction division takes place in the microsporangia present on the microsporophylls (producing pollen grains) and on the megasporangia present on the megasporophylls (producing megaspores).

Angiosperm – In angiosperms, the main plant-body is sporophytic and bears flowers. The male sex organ in the flower is the stamen, while the female sex organ is the pistil. Reduction division takes place in the anthers of the stamen (producing haploid pollen grains) and in the ovary of the pistil (producing eggs).

Archegonium is the female sex organ that produces the female gamete or egg. It is present in the life cycles of bryophytes, pteridophytes, and gymnosperms.

Life cycle of a fern (Dryopteris)

Dryopteris is a common fern with pinnately-compound leaves. The main plant-body is sporophytic. Many sporangia are borne on the lower surfaces of its mature leaves. Each sporangium has spore mother cells which undergo meiosis to produce haploid spores. On maturing, these spores dehisce and germinate to give rise to a heart-shaped gametophyte called prothallus.The prothallus bears the male and female sex organs called antheridia and archegonia respectively. The antheridia produce sperms that swim in water to reach the archegonia. The egg is produced by the archegonia. As a result of fertilisation, a zygote is formed. The zygote forms an embryo, which in turn develops into a new sporophyte. The young plant comes out of the archegonium

(a) Protonemal cell of a moss – Haploid

(b) Primary endosperm nucleus in a dicot – Triploid

(c) Leaf cell of a moss – Haploid

(d) Prothallus of a fern – Haploid

(e) Gemma cell in Marchantia – Haploid

(f) Meristem cell of a monocot – Diploid

(g) Ovum of a liverwort – Haploid

(h) Zygote of a fern – Diploid

Economic importance of algae

Algae have diverse economic uses. They perform half of the total carbon dioxide-fixation on earth by photosynthesis, acting as the primary producers in aquatic habitats.

(a) Food source: Many species of marine algae such as Porphyra, Sargassum, and Laminaria are edible. Chlorella and Spirulina are rich in proteins. Thus, they are used as food supplements.

(b) Commercial importance: Agar is used in the preparation of jellies and ice-cream. It is obtained from Gelidium and Gracilaria. Carrageenin is used as an emulsifier in chocolates, paints, and toothpastes. It is obtained from the red algae.

(c) Medicines: Many red algae such as Corallina are used in treating worm infections.

Economic importance of gymnosperms

(a) Construction purposes: Many conifers such as pine, cedar, etc., are sources of the soft wood used in construction and packing.

(b) Medicinal uses: An anticancer drug Taxol is obtained from Taxus. Many species of Ephedra produce ephedrine, which can be used in the treatment of asthma and bronchitis.

(c) Food source: The seeds of Pinus gerardiana (known as chilgoza) are edible.

(d) Source of resins: Resins are used commercially for manufacturing sealing waxes and water-proof paints. A type of resin known as turpentine is obtained from various species of Pinus.

Gymnosperms and angiosperms are seed-producing plants with diplontic life cycles.

In gymnosperms, the sporophylls are aggregated to form compact cones. The microsporophylls are broad and are not distinguished into filaments and anthers. The megasporophylls are woody and lack the ovary, style, and stigma, because of which the ovules lie exposed. The female gametophyte consists of archegonia. The fertilisation process involves the fusion of a male gamete with the female gamete. Their endosperm is haploid. The produced seeds are naked as there is no fruit formation.

Angiosperms are also known as flowering plants. They have sporophylls that aggregate to form flowers with the perianth. The microsporophylls consist of stamens containing pollen sacs. These sacs bear the male gametes called pollen grains. The megasporophylls are delicate and rolled, forming carpels that contain the ovary, style, and stigma. The ovules are present inside the ovary. The archegonium is replaced by an egg apparatus. Two male gametes enter the egg apparatus at the time of fertilisation. One male gamete fertilises the egg and the other fuses with the diploid secondary nucleus to form an endosperm. The resulting endosperm is thus triploid. In addition, in angiosperms, the development of seeds takes place inside the fruits.

Heterospory is a phenomenon in which two kinds of spores are borne by the same plant. These spores differ in size. The smaller one is known as microspore and the larger one is known as megaspore. The microspore germinates to form the male gametophyte and the megaspore germinates to form the female gametophyte. The male gametophyte releases the male gametes and these reach the female gametophyte to fuse with the egg. The development of the zygote takes place inside the female gametophyte.

This retention and germination of the megaspore within the megasporangium ensures proper development of the zygote. The zygote develops into the future sporophyte. The evolution of the seed habit is related to the retention of the megaspore.

Heterospory is thus considered an important step in evolution as it is a precursor to the seed habit.

Heterospory evolved first in pteridophytes such as Selaginella and Salvinia.

(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.

(i) Red algae and brown algae

(ii) Liverworts and moss

(iii) Homosporous and heterosporous pteridophyte

(iv) Syngamy and triple fusion

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

Match the followings (column I with column II)

Answer 11:

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.

Bryophytes need water for at least one stage of their life cycle. This is similar to Amphibians which also need water to lay eggs and their tadpoles develop in water. Hence, bryophytes are called the amphibians of the plant kingdom.

Structure	Pteridophyte	Gymnosperm	Angiosperm
Main reproductive part	Gametophyte bears antheridia and archegonia	Microsporophylls andmegasporophylls represent the gametophyte.	Flower bear antheridium an gynoecium.
Male reproductive part	Antheridia produce the malegamete.	The male cone is highlyreduced in size.	Antheridia are composed of an anther and a slender stalk. Anther produces the pollen grains, i.e. male gametes.
Female reproductive part	Archegonia produce the female gamete.	The megasporophyll is large in size and is easily apparent as the female cone.	The gynoecium contains the ovary, style and stigma. Fertilised egg develops inside the ovary and eventually seeds are produced.

Heterospory involves formation of two types of spores. Microspores are smaller in size and megaspores are much larger in size. In some Pteridophytes, the microspores and megaspore germinate to give rise to male and female gametophytes respectively. Finally, the zygote develops inside the female gametophyte. From evolutionary perspective, this is a precursor of seed habit in higher plants. Seeds have  enabled gymnosperms and angiosperms to tide over long p e r i o d s  of unfavourable conditions. Seeds have also enabled them to spread to wider geographical area through seed dispersal. It has indeed helped these plants in further evolution.
 

In case of Selaginella, the development of zygote into embryo takes place within the female gametophyte. This female gametophyte is retained on the parent plant for variable periods .  This is considered as a precursor of seed habit because advanced version of this phenomenon is seen in higher plants; like gymnosperms and angiosperms.  

But unlike seeds in higher plants; the embryo in Selaginella needs to quickly develop to begin the new generation. However, there could be temporary suspension of embryo growth; which is similar to seed dormancy in higher plants. 
 
 

Cycas is considered as a living fossil because it is the only living species in the family Cycadaceae. All other species of this family are now extinct. This plant is often considered as the plant of the Old World; which means it is found only at those places which can be associated with some of the oldest rocks in the world. Due to these reasons; it is called as the ‘relic of the past’. Moreover, Cycas shows more resemblance with Pteridophytes than Gymnosperms. This shows phylogenetic relationship between Pteridophytes and Gymnosperms. Some of the characters of Cycas which indicate towards this are as follows: 
(a) Seeds are shed when the embryo is still mature. In other gymnosperms; seeds are shed only when the embryo is mature.
(b) The megasporophyllus appears like leaf.
(c) In spite of the presence of pollen tubes, male gametes are flagellate.
(d) Leaf base is persistent.
(e) Circinate ptysix; which is similar as in Pteridophytes. 

Heterospory in pteridophytes leads to development of two different kinds of spores, i.e. microspores and megaspores. This is similar to higher plants in which male gametes are much smaller than female gametes. Another important feature is in situ development of embryo; which is similar to development of embryo in higher plants. Development of embryo inside the female gametophyte enables it to take nutrition from the female 
gametophyte. This is beneficial for proper development of embryo and give certain survival bene fits to the embryo. Thus, it can be said that heterospory in pteridophytes is a precursor to seed habit in gymnosperm.

. Fern (pteridophytes) exhibit haplo-diplontic condition. In this condition; both the gametophytic and sporophytic phases are multicellular. The diploid sporophyte is represented by a dominant, independent, photosynthetic, vascular plant body. The haploid gametophyte is also independent but it lives for a shorter duration than the sporophyte generation. The following figure shows the life cycle of plant showing haplodiplontic
condition.
 

Nature of Fern Prothallus:
The prothallus represents the haploid gametophytic generation. This is multicellular, ndependent, photosynthetic form which lives for a short duration. The prothallus needs cool, damp and shady place to grow. Due to its requirement of water for fertilization, pteridophytes are restricted to narrow geographical regions. 

Male gametophyte of pteridophyte	Male gametophyte of gymnosperm
(i) Distinct male gametophyte may not be present.	(i) Distinct male gametophyte is always present.
(ii) Antheridium is present.	(ii) Antheridium is absent.
(iii) Male gametes are flagellated.	(iii) Male gametes may or may not be flagellated
(iv) Male gametes need water as a medium to swim up to the female gamete.	(iv) Male gametes reach the female gamete through pollen tube. Water is not required for this purpose.

Mycorrhiza: It is a symbiotic association between a fungus and the roots of a vascular plant. Mycorrhiza is found in some genus of gymnosperms; like Pinus.
Coralloid Roots: These roots too show symbiotic association but in this case, the association is with nitrogen fixing cyanobacteria. Many nodules are formed in the roots giving them coralloid appearance. Examples are Cycas and plants of leguminoceae.
 

Mannitol is the reserve food material in Phaeophyceae or Brown Algae.
 

(a) Volvox, Spirogyra
(b) Fucus
(c) Polysiphonia
 

Rhizome

(a) Ectocarpus, Polysiphonia
(b) Fucus

Antheridium, Archegonium

(c) Monera

(c) Anisogamy 

Size of gametes is dissimilar and hence term ‘Anisogamy’ is used. 

Ans. (c) Phaeophyceae

Ans. (d) Bryophytes
Plants from monocots and gymnosperms do not need water for fertilization. Byrophytes and pteridophytes need water for fertilization. But
pteridophytes have true roots. Hence, ‘d’ is the correct option. 

Ans. (c) A gametophyte free living structure formed in pteridophytes

Ans. (d) Gymnosperms
Cones are salient features of gymnosperms. Moreover, gymnosperms are well adapted to extreme conditions. 

Ans. (b) 7 cells and 8 nuclei
The seven cells are; one egg cell, two synergids, three antipodal cells and one secondary nucleus. The secondary nucleus contains two nuclei; while the other cells contain one nucleus each.

Ans. (c) 54
Endosperm is formed after fusion between a haploid male gamete and diploid secondary nucleus. Thus, endosperm has triploid nucleus; which will have three times the number of chromosomes as in a haploid nucleus. 

Ans. (a) Haploid and is found in mosses
 

Ans. (d) Gymnosperm
Redwood trees is a Gymnosperm which have earned many sobriquets; like tallest tree, oldest tree, largest by trunk volume, etc. 
 

In bryophytes, the dominant phase is represented by  gametophytic plant. The gametophyte is independent, photosynthetic, thalloid phase. Antheridia and archegonia are formed on the gametophye. These organs are multicellular. These organs bear the respective gametes, viz. male and female. The antheridium produces biflagellate antherozoids. The archegonium is flask-shaped. It produces a single egg.

Transfer of antherozoids to the archegonium take place through water. Flagella in the a ntherozoids facilitate motility. Zygote is formed after fertilization. But the zygote does not undergo meiosis immediately after fertilization. It develops into a multicellular body called sporophyte.
The sporophyte in bryophytes is much smaller and is not independent but attached to the gametophyte. It gets nutrition from the gametophyte. It is clear that the gametophyte is dominant phase in the life cycle of  a bryophyte in every aspect. Gametophyte is  independent and photosynthetic. It is much larger in size compared to the sporophyte.  
On the other hand, the sporophyte is not free-living but remains attached to the gametophyte so that it can get nutrition. 

Both pteridophyte and bryophyte show haplo-diplontic life cycle. While the diploid phase is not independent in bryophytes, it is independent in pteridophytes. Moreover, the  sporophyte is more conspicuous in pteridophytes than in bryophytes. Sporophyte is the dominant phase in life cycle of pteridophyte.
The given figure shows the haplo-diplontic life cycle. 

Sporophyte: The sporophyte is well developed plant body.
It is differentiated into true roots, stem and leaves. Vascular tissue is well developed in these parts of the plant. The sporophyte bears the sporangia. Sporangia are subtended by leaf-like appendages called sporophylls. 

Formation of Spores: The spore mother cells in the sporangia undergo reduction division to produce spores.

Germination of Spores: Spores germinate to produce the gametophyte.

Gametophyte: Gametophyte is small but multicellular. It is free-living and usually photosynthetic. It is called prothallus. It bears antheridia and archegonia which produce male and female gametes. Transfer of male gamete takes place through pollen tube and then fertilization takes place. 

Both pteridophyte and bryophyte show haplo-diplontic life cycle. While the diploid phase is not independent in bryophytes, it is independent in pteridophytes. Moreover, the  sporophyte is more conspicuous in pteridophytes than in bryophytes. Sporophyte is the dominant phase in life cycle of pteridophyte.
The given figure shows the haplo-diplontic life cycle. 

Sporophyte: The sporophyte is well developed plant body.
It is differentiated into true roots, stem and leaves. Vascular tissue is well developed in these parts of the plant. The sporophyte bears the sporangia. Sporangia are subtended by leaf-like appendages called sporophylls. 

Formation of Spores: The spore mother cells in the sporangia undergo reduction division to produce spores.

Germination of Spores: Spores germinate to produce the gametophyte.

Gametophyte: Gametophyte is small but multicellular. It is free-living and usually photosynthetic. It is called prothallus. It bears antheridia and archegonia which produce male and female gametes. Transfer of male gamete takes place through pollen tube and then fertilization takes place. 

Ans. Option ‘b’ is the correct option, i.e. both will die.
Symbiosis: This is defined as a relationship between two organisms in which both the organisms get benefit from each other. There can be many examples of symbiotic relationship in which removal of one may not result in death of another partner. For example; in case of symbiotic relationship between a bird and a buffalo, the worms and insects on buffalo’s back are not the only source of food for the bird. Similarly, there can
be some other ways for the buffalo to get rid of those pests.
But in case of lichen; both the fungal and algal components depend on each other for their basic needs. In this case, alga is the only source of food for the fungal component. 
Similarly, fungus is the only source of water and minerals for the alga. They have no alternative means to fulfill their need and hence in case of removal of any one partner, another partner would die. 
 
Since it is a relationship of mutual benefit hence it will still be called symbiosis. 

In angiosperms; one of the male gamete fuses with the female gamete. Additionally, another male gamete fuses with the secondary nucleus. Fusion between male and female gametes results in formation of the zygote. Apart from that, fusion between another male gamete and the secondary nucleus results in formation of the primary endosperm nucleus (PEN). Since, two instances of fusion of nuclei take place hence it is called double fertilization. Two following figure shows double fertilization:  

(a) Liverwort 

(b) Funaria, Gametophyte and sporophyte 

(c) Alternation of generation in Angiosperm 

Algae are classified into three main classes – Chlorophyceae, Phaeophyceae, and Rhodophyceae. These divisions are based on the following factors:

(a) Major photosynthetic pigments present

(b) Form of stored food

(c) Cell wall composition

(d) Number of flagella and position of insertion

Class I – Chlorophyceae

Common name – Green algae

Major pigments – Chlorophylls a and b

Stored food – Starch

Cell wall composition – Cellulose

Flagella number and position – 2-8; equal and apical

Class II – Phaeophyceae

Common name– Brown algae

Major pigments – Chlorophylls a and c, and fucoxanthin

Stored food – Mannitol and laminarin

Cell wall composition – Cellulose and algin

Flagella number and position – 2; unequal and lateral

Class III­ – Rhodophyceae

Common name – Red algae

Major pigments – Chlorophylls a and d, and phycoerythrin

Stored food –­ Floridean starch

Cell wall – Cellulose, pectin, and polysulphate esters

Flagella number – Absent

Liverwort – In liverworts, the main plant-body is haploid (gametophytic). It bears the male and female sex organs which produce gametes. These gametes fuse to form a zygote. The zygote develops on the gametophytic plant-body to form a sporophyte. The sporophyte is differentiated into the foot, seta, and capsule. Many haploid spores are produced as a result of the reduction division taking place inside the capsule.

Moss – In mosses, the primary protonema (developed in the first stage) develops into the secondary protonema. Both these stages are haploid or gametophytic. The secondary protonema bears the sex organs which produce gametes. These gametes fuse to form a zygote. The zygote develops into a sporophyte. Many spores are formed as a result of the reduction division taking place in the capsule of this sporophyte.

Fern – In ferns, the main plant-body is sporophytic. Its leaves are known as sporophylls and these bear the sporangia. Reduction division takes place in these sporangia, thereby producing many spores.

Gymnosperm – In gymnosperms, the main plant-body is sporophytic. They bear two types of leaves – microsporophylls and megasporophylls. Reduction division takes place in the microsporangia present on the microsporophylls (producing pollen grains) and on the megasporangia present on the megasporophylls (producing megaspores).

Angiosperm – In angiosperms, the main plant-body is sporophytic and bears flowers. The male sex organ in the flower is the stamen, while the female sex organ is the pistil. Reduction division takes place in the anthers of the stamen (producing haploid pollen grains) and in the ovary of the pistil (producing eggs).

Archegonium is the female sex organ that produces the female gamete or egg. It is present in the life cycles of bryophytes, pteridophytes, and gymnosperms.

Life cycle of a fern (Dryopteris)

Dryopteris is a common fern with pinnately-compound leaves. The main plant-body is sporophytic. Many sporangia are borne on the lower surfaces of its mature leaves. Each sporangium has spore mother cells which undergo meiosis to produce haploid spores. On maturing, these spores dehisce and germinate to give rise to a heart-shaped gametophyte called prothallus.The prothallus bears the male and female sex organs called antheridia and archegonia respectively. The antheridia produce sperms that swim in water to reach the archegonia. The egg is produced by the archegonia. As a result of fertilisation, a zygote is formed. The zygote forms an embryo, which in turn develops into a new sporophyte. The young plant comes out of the archegonium

(a) Protonemal cell of a moss – Haploid

(b) Primary endosperm nucleus in a dicot – Triploid

(c) Leaf cell of a moss – Haploid

(d) Prothallus of a fern – Haploid

(e) Gemma cell in Marchantia – Haploid

(f) Meristem cell of a monocot – Diploid

(g) Ovum of a liverwort – Haploid

(h) Zygote of a fern – Diploid

Economic importance of algae

Algae have diverse economic uses. They perform half of the total carbon dioxide-fixation on earth by photosynthesis, acting as the primary producers in aquatic habitats.

(a) Food source: Many species of marine algae such as Porphyra, Sargassum, and Laminaria are edible. Chlorella and Spirulina are rich in proteins. Thus, they are used as food supplements.

(b) Commercial importance: Agar is used in the preparation of jellies and ice-cream. It is obtained from Gelidium and Gracilaria. Carrageenin is used as an emulsifier in chocolates, paints, and toothpastes. It is obtained from the red algae.

(c) Medicines: Many red algae such as Corallina are used in treating worm infections.

Economic importance of gymnosperms

(a) Construction purposes: Many conifers such as pine, cedar, etc., are sources of the soft wood used in construction and packing.

(b) Medicinal uses: An anticancer drug Taxol is obtained from Taxus. Many species of Ephedra produce ephedrine, which can be used in the treatment of asthma and bronchitis.

(c) Food source: The seeds of Pinus gerardiana (known as chilgoza) are edible.

(d) Source of resins: Resins are used commercially for manufacturing sealing waxes and water-proof paints. A type of resin known as turpentine is obtained from various species of Pinus.

Gymnosperms and angiosperms are seed-producing plants with diplontic life cycles.

In gymnosperms, the sporophylls are aggregated to form compact cones. The microsporophylls are broad and are not distinguished into filaments and anthers. The megasporophylls are woody and lack the ovary, style, and stigma, because of which the ovules lie exposed. The female gametophyte consists of archegonia. The fertilisation process involves the fusion of a male gamete with the female gamete. Their endosperm is haploid. The produced seeds are naked as there is no fruit formation.

Angiosperms are also known as flowering plants. They have sporophylls that aggregate to form flowers with the perianth. The microsporophylls consist of stamens containing pollen sacs. These sacs bear the male gametes called pollen grains. The megasporophylls are delicate and rolled, forming carpels that contain the ovary, style, and stigma. The ovules are present inside the ovary. The archegonium is replaced by an egg apparatus. Two male gametes enter the egg apparatus at the time of fertilisation. One male gamete fertilises the egg and the other fuses with the diploid secondary nucleus to form an endosperm. The resulting endosperm is thus triploid. In addition, in angiosperms, the development of seeds takes place inside the fruits.

Heterospory is a phenomenon in which two kinds of spores are borne by the same plant. These spores differ in size. The smaller one is known as microspore and the larger one is known as megaspore. The microspore germinates to form the male gametophyte and the megaspore germinates to form the female gametophyte. The male gametophyte releases the male gametes and these reach the female gametophyte to fuse with the egg. The development of the zygote takes place inside the female gametophyte.

This retention and germination of the megaspore within the megasporangium ensures proper development of the zygote. The zygote develops into the future sporophyte. The evolution of the seed habit is related to the retention of the megaspore.

Heterospory is thus considered an important step in evolution as it is a precursor to the seed habit.

Heterospory evolved first in pteridophytes such as Selaginella and Salvinia.

(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.

(i) Red algae and brown algae

(ii) Liverworts and moss

(iii) Homosporous and heterosporous pteridophyte

(iv) Syngamy and triple fusion

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

Match the followings (column I with column II)

Answer 11:

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.

Bryophytes need water for at least one stage of their life cycle. This is similar to Amphibians which also need water to lay eggs and their tadpoles develop in water. Hence, bryophytes are called the amphibians of the plant kingdom.

Structure	Pteridophyte	Gymnosperm	Angiosperm
Main reproductive part	Gametophyte bears antheridia and archegonia	Microsporophylls andmegasporophylls represent the gametophyte.	Flower bear antheridium an gynoecium.
Male reproductive part	Antheridia produce the malegamete.	The male cone is highlyreduced in size.	Antheridia are composed of an anther and a slender stalk. Anther produces the pollen grains, i.e. male gametes.
Female reproductive part	Archegonia produce the female gamete.	The megasporophyll is large in size and is easily apparent as the female cone.	The gynoecium contains the ovary, style and stigma. Fertilised egg develops inside the ovary and eventually seeds are produced.

Heterospory involves formation of two types of spores. Microspores are smaller in size and megaspores are much larger in size. In some Pteridophytes, the microspores and megaspore germinate to give rise to male and female gametophytes respectively. Finally, the zygote develops inside the female gametophyte. From evolutionary perspective, this is a precursor of seed habit in higher plants. Seeds have  enabled gymnosperms and angiosperms to tide over long p e r i o d s  of unfavourable conditions. Seeds have also enabled them to spread to wider geographical area through seed dispersal. It has indeed helped these plants in further evolution.
 

In case of Selaginella, the development of zygote into embryo takes place within the female gametophyte. This female gametophyte is retained on the parent plant for variable periods .  This is considered as a precursor of seed habit because advanced version of this phenomenon is seen in higher plants; like gymnosperms and angiosperms.  

But unlike seeds in higher plants; the embryo in Selaginella needs to quickly develop to begin the new generation. However, there could be temporary suspension of embryo growth; which is similar to seed dormancy in higher plants. 
 
 

Cycas is considered as a living fossil because it is the only living species in the family Cycadaceae. All other species of this family are now extinct. This plant is often considered as the plant of the Old World; which means it is found only at those places which can be associated with some of the oldest rocks in the world. Due to these reasons; it is called as the ‘relic of the past’. Moreover, Cycas shows more resemblance with Pteridophytes than Gymnosperms. This shows phylogenetic relationship between Pteridophytes and Gymnosperms. Some of the characters of Cycas which indicate towards this are as follows: 
(a) Seeds are shed when the embryo is still mature. In other gymnosperms; seeds are shed only when the embryo is mature.
(b) The megasporophyllus appears like leaf.
(c) In spite of the presence of pollen tubes, male gametes are flagellate.
(d) Leaf base is persistent.
(e) Circinate ptysix; which is similar as in Pteridophytes. 

Heterospory in pteridophytes leads to development of two different kinds of spores, i.e. microspores and megaspores. This is similar to higher plants in which male gametes are much smaller than female gametes. Another important feature is in situ development of embryo; which is similar to development of embryo in higher plants. Development of embryo inside the female gametophyte enables it to take nutrition from the female 
gametophyte. This is beneficial for proper development of embryo and give certain survival bene fits to the embryo. Thus, it can be said that heterospory in pteridophytes is a precursor to seed habit in gymnosperm.

. Fern (pteridophytes) exhibit haplo-diplontic condition. In this condition; both the gametophytic and sporophytic phases are multicellular. The diploid sporophyte is represented by a dominant, independent, photosynthetic, vascular plant body. The haploid gametophyte is also independent but it lives for a shorter duration than the sporophyte generation. The following figure shows the life cycle of plant showing haplodiplontic
condition.
 

Nature of Fern Prothallus:
The prothallus represents the haploid gametophytic generation. This is multicellular, ndependent, photosynthetic form which lives for a short duration. The prothallus needs cool, damp and shady place to grow. Due to its requirement of water for fertilization, pteridophytes are restricted to narrow geographical regions. 

Male gametophyte of pteridophyte	Male gametophyte of gymnosperm
(i) Distinct male gametophyte may not be present.	(i) Distinct male gametophyte is always present.
(ii) Antheridium is present.	(ii) Antheridium is absent.
(iii) Male gametes are flagellated.	(iii) Male gametes may or may not be flagellated
(iv) Male gametes need water as a medium to swim up to the female gamete.	(iv) Male gametes reach the female gamete through pollen tube. Water is not required for this purpose.

Mycorrhiza: It is a symbiotic association between a fungus and the roots of a vascular plant. Mycorrhiza is found in some genus of gymnosperms; like Pinus.
Coralloid Roots: These roots too show symbiotic association but in this case, the association is with nitrogen fixing cyanobacteria. Many nodules are formed in the roots giving them coralloid appearance. Examples are Cycas and plants of leguminoceae.
 

Mannitol is the reserve food material in Phaeophyceae or Brown Algae.
 

(a) Volvox, Spirogyra
(b) Fucus
(c) Polysiphonia
 

Rhizome

(a) Ectocarpus, Polysiphonia
(b) Fucus

Antheridium, Archegonium

(c) Monera

(c) Anisogamy 

Size of gametes is dissimilar and hence term ‘Anisogamy’ is used. 

Ans. (c) Phaeophyceae

Ans. (d) Bryophytes
Plants from monocots and gymnosperms do not need water for fertilization. Byrophytes and pteridophytes need water for fertilization. But
pteridophytes have true roots. Hence, ‘d’ is the correct option. 

Ans. (c) A gametophyte free living structure formed in pteridophytes

Ans. (d) Gymnosperms
Cones are salient features of gymnosperms. Moreover, gymnosperms are well adapted to extreme conditions. 

Ans. (b) 7 cells and 8 nuclei
The seven cells are; one egg cell, two synergids, three antipodal cells and one secondary nucleus. The secondary nucleus contains two nuclei; while the other cells contain one nucleus each.

Ans. (c) 54
Endosperm is formed after fusion between a haploid male gamete and diploid secondary nucleus. Thus, endosperm has triploid nucleus; which will have three times the number of chromosomes as in a haploid nucleus. 

Ans. (a) Haploid and is found in mosses
 

Ans. (d) Gymnosperm
Redwood trees is a Gymnosperm which have earned many sobriquets; like tallest tree, oldest tree, largest by trunk volume, etc. 
 

In bryophytes, the dominant phase is represented by  gametophytic plant. The gametophyte is independent, photosynthetic, thalloid phase. Antheridia and archegonia are formed on the gametophye. These organs are multicellular. These organs bear the respective gametes, viz. male and female. The antheridium produces biflagellate antherozoids. The archegonium is flask-shaped. It produces a single egg.

Transfer of antherozoids to the archegonium take place through water. Flagella in the a ntherozoids facilitate motility. Zygote is formed after fertilization. But the zygote does not undergo meiosis immediately after fertilization. It develops into a multicellular body called sporophyte.
The sporophyte in bryophytes is much smaller and is not independent but attached to the gametophyte. It gets nutrition from the gametophyte. It is clear that the gametophyte is dominant phase in the life cycle of  a bryophyte in every aspect. Gametophyte is  independent and photosynthetic. It is much larger in size compared to the sporophyte.  
On the other hand, the sporophyte is not free-living but remains attached to the gametophyte so that it can get nutrition. 

Both pteridophyte and bryophyte show haplo-diplontic life cycle. While the diploid phase is not independent in bryophytes, it is independent in pteridophytes. Moreover, the  sporophyte is more conspicuous in pteridophytes than in bryophytes. Sporophyte is the dominant phase in life cycle of pteridophyte.
The given figure shows the haplo-diplontic life cycle. 

Sporophyte: The sporophyte is well developed plant body.
It is differentiated into true roots, stem and leaves. Vascular tissue is well developed in these parts of the plant. The sporophyte bears the sporangia. Sporangia are subtended by leaf-like appendages called sporophylls. 

Formation of Spores: The spore mother cells in the sporangia undergo reduction division to produce spores.

Germination of Spores: Spores germinate to produce the gametophyte.

Gametophyte: Gametophyte is small but multicellular. It is free-living and usually photosynthetic. It is called prothallus. It bears antheridia and archegonia which produce male and female gametes. Transfer of male gamete takes place through pollen tube and then fertilization takes place. 

Both pteridophyte and bryophyte show haplo-diplontic life cycle. While the diploid phase is not independent in bryophytes, it is independent in pteridophytes. Moreover, the  sporophyte is more conspicuous in pteridophytes than in bryophytes. Sporophyte is the dominant phase in life cycle of pteridophyte.
The given figure shows the haplo-diplontic life cycle. 

Sporophyte: The sporophyte is well developed plant body.
It is differentiated into true roots, stem and leaves. Vascular tissue is well developed in these parts of the plant. The sporophyte bears the sporangia. Sporangia are subtended by leaf-like appendages called sporophylls. 

Formation of Spores: The spore mother cells in the sporangia undergo reduction division to produce spores.

Germination of Spores: Spores germinate to produce the gametophyte.

Gametophyte: Gametophyte is small but multicellular. It is free-living and usually photosynthetic. It is called prothallus. It bears antheridia and archegonia which produce male and female gametes. Transfer of male gamete takes place through pollen tube and then fertilization takes place. 

Ans. Option ‘b’ is the correct option, i.e. both will die.
Symbiosis: This is defined as a relationship between two organisms in which both the organisms get benefit from each other. There can be many examples of symbiotic relationship in which removal of one may not result in death of another partner. For example; in case of symbiotic relationship between a bird and a buffalo, the worms and insects on buffalo’s back are not the only source of food for the bird. Similarly, there can
be some other ways for the buffalo to get rid of those pests.
But in case of lichen; both the fungal and algal components depend on each other for their basic needs. In this case, alga is the only source of food for the fungal component. 
Similarly, fungus is the only source of water and minerals for the alga. They have no alternative means to fulfill their need and hence in case of removal of any one partner, another partner would die. 
 
Since it is a relationship of mutual benefit hence it will still be called symbiosis. 

In angiosperms; one of the male gamete fuses with the female gamete. Additionally, another male gamete fuses with the secondary nucleus. Fusion between male and female gametes results in formation of the zygote. Apart from that, fusion between another male gamete and the secondary nucleus results in formation of the primary endosperm nucleus (PEN). Since, two instances of fusion of nuclei take place hence it is called double fertilization. Two following figure shows double fertilization:  

(a) Liverwort 

(b) Funaria, Gametophyte and sporophyte 

(c) Alternation of generation in Angiosperm 

Algae are classified into three main classes – Chlorophyceae, Phaeophyceae, and Rhodophyceae. These divisions are based on the following factors:

(a) Major photosynthetic pigments present

(b) Form of stored food

(c) Cell wall composition

(d) Number of flagella and position of insertion

Class I – Chlorophyceae

Common name – Green algae

Major pigments – Chlorophylls a and b

Stored food – Starch

Cell wall composition – Cellulose

Flagella number and position – 2-8; equal and apical

Class II – Phaeophyceae

Common name– Brown algae

Major pigments – Chlorophylls a and c, and fucoxanthin

Stored food – Mannitol and laminarin

Cell wall composition – Cellulose and algin

Flagella number and position – 2; unequal and lateral

Class III­ – Rhodophyceae

Common name – Red algae

Major pigments – Chlorophylls a and d, and phycoerythrin

Stored food –­ Floridean starch

Cell wall – Cellulose, pectin, and polysulphate esters

Flagella number – Absent

Liverwort – In liverworts, the main plant-body is haploid (gametophytic). It bears the male and female sex organs which produce gametes. These gametes fuse to form a zygote. The zygote develops on the gametophytic plant-body to form a sporophyte. The sporophyte is differentiated into the foot, seta, and capsule. Many haploid spores are produced as a result of the reduction division taking place inside the capsule.

Moss – In mosses, the primary protonema (developed in the first stage) develops into the secondary protonema. Both these stages are haploid or gametophytic. The secondary protonema bears the sex organs which produce gametes. These gametes fuse to form a zygote. The zygote develops into a sporophyte. Many spores are formed as a result of the reduction division taking place in the capsule of this sporophyte.

Fern – In ferns, the main plant-body is sporophytic. Its leaves are known as sporophylls and these bear the sporangia. Reduction division takes place in these sporangia, thereby producing many spores.

Gymnosperm – In gymnosperms, the main plant-body is sporophytic. They bear two types of leaves – microsporophylls and megasporophylls. Reduction division takes place in the microsporangia present on the microsporophylls (producing pollen grains) and on the megasporangia present on the megasporophylls (producing megaspores).

Angiosperm – In angiosperms, the main plant-body is sporophytic and bears flowers. The male sex organ in the flower is the stamen, while the female sex organ is the pistil. Reduction division takes place in the anthers of the stamen (producing haploid pollen grains) and in the ovary of the pistil (producing eggs).

Archegonium is the female sex organ that produces the female gamete or egg. It is present in the life cycles of bryophytes, pteridophytes, and gymnosperms.

Life cycle of a fern (Dryopteris)

Dryopteris is a common fern with pinnately-compound leaves. The main plant-body is sporophytic. Many sporangia are borne on the lower surfaces of its mature leaves. Each sporangium has spore mother cells which undergo meiosis to produce haploid spores. On maturing, these spores dehisce and germinate to give rise to a heart-shaped gametophyte called prothallus.The prothallus bears the male and female sex organs called antheridia and archegonia respectively. The antheridia produce sperms that swim in water to reach the archegonia. The egg is produced by the archegonia. As a result of fertilisation, a zygote is formed. The zygote forms an embryo, which in turn develops into a new sporophyte. The young plant comes out of the archegonium

(a) Protonemal cell of a moss – Haploid

(b) Primary endosperm nucleus in a dicot – Triploid

(c) Leaf cell of a moss – Haploid

(d) Prothallus of a fern – Haploid

(e) Gemma cell in Marchantia – Haploid

(f) Meristem cell of a monocot – Diploid

(g) Ovum of a liverwort – Haploid

(h) Zygote of a fern – Diploid

Economic importance of algae

Algae have diverse economic uses. They perform half of the total carbon dioxide-fixation on earth by photosynthesis, acting as the primary producers in aquatic habitats.

(a) Food source: Many species of marine algae such as Porphyra, Sargassum, and Laminaria are edible. Chlorella and Spirulina are rich in proteins. Thus, they are used as food supplements.

(b) Commercial importance: Agar is used in the preparation of jellies and ice-cream. It is obtained from Gelidium and Gracilaria. Carrageenin is used as an emulsifier in chocolates, paints, and toothpastes. It is obtained from the red algae.

(c) Medicines: Many red algae such as Corallina are used in treating worm infections.

Economic importance of gymnosperms

(a) Construction purposes: Many conifers such as pine, cedar, etc., are sources of the soft wood used in construction and packing.

(b) Medicinal uses: An anticancer drug Taxol is obtained from Taxus. Many species of Ephedra produce ephedrine, which can be used in the treatment of asthma and bronchitis.

(c) Food source: The seeds of Pinus gerardiana (known as chilgoza) are edible.

(d) Source of resins: Resins are used commercially for manufacturing sealing waxes and water-proof paints. A type of resin known as turpentine is obtained from various species of Pinus.

Gymnosperms and angiosperms are seed-producing plants with diplontic life cycles.

In gymnosperms, the sporophylls are aggregated to form compact cones. The microsporophylls are broad and are not distinguished into filaments and anthers. The megasporophylls are woody and lack the ovary, style, and stigma, because of which the ovules lie exposed. The female gametophyte consists of archegonia. The fertilisation process involves the fusion of a male gamete with the female gamete. Their endosperm is haploid. The produced seeds are naked as there is no fruit formation.

Angiosperms are also known as flowering plants. They have sporophylls that aggregate to form flowers with the perianth. The microsporophylls consist of stamens containing pollen sacs. These sacs bear the male gametes called pollen grains. The megasporophylls are delicate and rolled, forming carpels that contain the ovary, style, and stigma. The ovules are present inside the ovary. The archegonium is replaced by an egg apparatus. Two male gametes enter the egg apparatus at the time of fertilisation. One male gamete fertilises the egg and the other fuses with the diploid secondary nucleus to form an endosperm. The resulting endosperm is thus triploid. In addition, in angiosperms, the development of seeds takes place inside the fruits.

Heterospory is a phenomenon in which two kinds of spores are borne by the same plant. These spores differ in size. The smaller one is known as microspore and the larger one is known as megaspore. The microspore germinates to form the male gametophyte and the megaspore germinates to form the female gametophyte. The male gametophyte releases the male gametes and these reach the female gametophyte to fuse with the egg. The development of the zygote takes place inside the female gametophyte.

This retention and germination of the megaspore within the megasporangium ensures proper development of the zygote. The zygote develops into the future sporophyte. The evolution of the seed habit is related to the retention of the megaspore.

Heterospory is thus considered an important step in evolution as it is a precursor to the seed habit.

Heterospory evolved first in pteridophytes such as Selaginella and Salvinia.

(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.

(i) Red algae and brown algae

(ii) Liverworts and moss

(iii) Homosporous and heterosporous pteridophyte

(iv) Syngamy and triple fusion

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

Match the followings (column I with column II)

Answer 11:

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.

Bryophytes need water for at least one stage of their life cycle. This is similar to Amphibians which also need water to lay eggs and their tadpoles develop in water. Hence, bryophytes are called the amphibians of the plant kingdom.

Structure	Pteridophyte	Gymnosperm	Angiosperm
Main reproductive part	Gametophyte bears antheridia and archegonia	Microsporophylls andmegasporophylls represent the gametophyte.	Flower bear antheridium an gynoecium.
Male reproductive part	Antheridia produce the malegamete.	The male cone is highlyreduced in size.	Antheridia are composed of an anther and a slender stalk. Anther produces the pollen grains, i.e. male gametes.
Female reproductive part	Archegonia produce the female gamete.	The megasporophyll is large in size and is easily apparent as the female cone.	The gynoecium contains the ovary, style and stigma. Fertilised egg develops inside the ovary and eventually seeds are produced.

Heterospory involves formation of two types of spores. Microspores are smaller in size and megaspores are much larger in size. In some Pteridophytes, the microspores and megaspore germinate to give rise to male and female gametophytes respectively. Finally, the zygote develops inside the female gametophyte. From evolutionary perspective, this is a precursor of seed habit in higher plants. Seeds have  enabled gymnosperms and angiosperms to tide over long p e r i o d s  of unfavourable conditions. Seeds have also enabled them to spread to wider geographical area through seed dispersal. It has indeed helped these plants in further evolution.
 

In case of Selaginella, the development of zygote into embryo takes place within the female gametophyte. This female gametophyte is retained on the parent plant for variable periods .  This is considered as a precursor of seed habit because advanced version of this phenomenon is seen in higher plants; like gymnosperms and angiosperms.  

But unlike seeds in higher plants; the embryo in Selaginella needs to quickly develop to begin the new generation. However, there could be temporary suspension of embryo growth; which is similar to seed dormancy in higher plants. 
 
 

Cycas is considered as a living fossil because it is the only living species in the family Cycadaceae. All other species of this family are now extinct. This plant is often considered as the plant of the Old World; which means it is found only at those places which can be associated with some of the oldest rocks in the world. Due to these reasons; it is called as the ‘relic of the past’. Moreover, Cycas shows more resemblance with Pteridophytes than Gymnosperms. This shows phylogenetic relationship between Pteridophytes and Gymnosperms. Some of the characters of Cycas which indicate towards this are as follows: 
(a) Seeds are shed when the embryo is still mature. In other gymnosperms; seeds are shed only when the embryo is mature.
(b) The megasporophyllus appears like leaf.
(c) In spite of the presence of pollen tubes, male gametes are flagellate.
(d) Leaf base is persistent.
(e) Circinate ptysix; which is similar as in Pteridophytes. 

Heterospory in pteridophytes leads to development of two different kinds of spores, i.e. microspores and megaspores. This is similar to higher plants in which male gametes are much smaller than female gametes. Another important feature is in situ development of embryo; which is similar to development of embryo in higher plants. Development of embryo inside the female gametophyte enables it to take nutrition from the female 
gametophyte. This is beneficial for proper development of embryo and give certain survival bene fits to the embryo. Thus, it can be said that heterospory in pteridophytes is a precursor to seed habit in gymnosperm.

. Fern (pteridophytes) exhibit haplo-diplontic condition. In this condition; both the gametophytic and sporophytic phases are multicellular. The diploid sporophyte is represented by a dominant, independent, photosynthetic, vascular plant body. The haploid gametophyte is also independent but it lives for a shorter duration than the sporophyte generation. The following figure shows the life cycle of plant showing haplodiplontic
condition.
 

Nature of Fern Prothallus:
The prothallus represents the haploid gametophytic generation. This is multicellular, ndependent, photosynthetic form which lives for a short duration. The prothallus needs cool, damp and shady place to grow. Due to its requirement of water for fertilization, pteridophytes are restricted to narrow geographical regions. 

Male gametophyte of pteridophyte	Male gametophyte of gymnosperm
(i) Distinct male gametophyte may not be present.	(i) Distinct male gametophyte is always present.
(ii) Antheridium is present.	(ii) Antheridium is absent.
(iii) Male gametes are flagellated.	(iii) Male gametes may or may not be flagellated
(iv) Male gametes need water as a medium to swim up to the female gamete.	(iv) Male gametes reach the female gamete through pollen tube. Water is not required for this purpose.

Mycorrhiza: It is a symbiotic association between a fungus and the roots of a vascular plant. Mycorrhiza is found in some genus of gymnosperms; like Pinus.
Coralloid Roots: These roots too show symbiotic association but in this case, the association is with nitrogen fixing cyanobacteria. Many nodules are formed in the roots giving them coralloid appearance. Examples are Cycas and plants of leguminoceae.
 

Mannitol is the reserve food material in Phaeophyceae or Brown Algae.
 

(a) Volvox, Spirogyra
(b) Fucus
(c) Polysiphonia
 

Rhizome

(a) Ectocarpus, Polysiphonia
(b) Fucus

Antheridium, Archegonium

(c) Monera

(c) Anisogamy 

Size of gametes is dissimilar and hence term ‘Anisogamy’ is used. 

Ans. (c) Phaeophyceae

Ans. (d) Bryophytes
Plants from monocots and gymnosperms do not need water for fertilization. Byrophytes and pteridophytes need water for fertilization. But
pteridophytes have true roots. Hence, ‘d’ is the correct option. 

Ans. (c) A gametophyte free living structure formed in pteridophytes

Ans. (d) Gymnosperms
Cones are salient features of gymnosperms. Moreover, gymnosperms are well adapted to extreme conditions. 

Ans. (b) 7 cells and 8 nuclei
The seven cells are; one egg cell, two synergids, three antipodal cells and one secondary nucleus. The secondary nucleus contains two nuclei; while the other cells contain one nucleus each.

Ans. (c) 54
Endosperm is formed after fusion between a haploid male gamete and diploid secondary nucleus. Thus, endosperm has triploid nucleus; which will have three times the number of chromosomes as in a haploid nucleus. 

Ans. (a) Haploid and is found in mosses
 

Ans. (d) Gymnosperm
Redwood trees is a Gymnosperm which have earned many sobriquets; like tallest tree, oldest tree, largest by trunk volume, etc. 
 

In bryophytes, the dominant phase is represented by  gametophytic plant. The gametophyte is independent, photosynthetic, thalloid phase. Antheridia and archegonia are formed on the gametophye. These organs are multicellular. These organs bear the respective gametes, viz. male and female. The antheridium produces biflagellate antherozoids. The archegonium is flask-shaped. It produces a single egg.

Transfer of antherozoids to the archegonium take place through water. Flagella in the a ntherozoids facilitate motility. Zygote is formed after fertilization. But the zygote does not undergo meiosis immediately after fertilization. It develops into a multicellular body called sporophyte.
The sporophyte in bryophytes is much smaller and is not independent but attached to the gametophyte. It gets nutrition from the gametophyte. It is clear that the gametophyte is dominant phase in the life cycle of  a bryophyte in every aspect. Gametophyte is  independent and photosynthetic. It is much larger in size compared to the sporophyte.  
On the other hand, the sporophyte is not free-living but remains attached to the gametophyte so that it can get nutrition. 

Both pteridophyte and bryophyte show haplo-diplontic life cycle. While the diploid phase is not independent in bryophytes, it is independent in pteridophytes. Moreover, the  sporophyte is more conspicuous in pteridophytes than in bryophytes. Sporophyte is the dominant phase in life cycle of pteridophyte.
The given figure shows the haplo-diplontic life cycle. 

Sporophyte: The sporophyte is well developed plant body.
It is differentiated into true roots, stem and leaves. Vascular tissue is well developed in these parts of the plant. The sporophyte bears the sporangia. Sporangia are subtended by leaf-like appendages called sporophylls. 

Formation of Spores: The spore mother cells in the sporangia undergo reduction division to produce spores.

Germination of Spores: Spores germinate to produce the gametophyte.

Gametophyte: Gametophyte is small but multicellular. It is free-living and usually photosynthetic. It is called prothallus. It bears antheridia and archegonia which produce male and female gametes. Transfer of male gamete takes place through pollen tube and then fertilization takes place. 

Both pteridophyte and bryophyte show haplo-diplontic life cycle. While the diploid phase is not independent in bryophytes, it is independent in pteridophytes. Moreover, the  sporophyte is more conspicuous in pteridophytes than in bryophytes. Sporophyte is the dominant phase in life cycle of pteridophyte.
The given figure shows the haplo-diplontic life cycle. 

Sporophyte: The sporophyte is well developed plant body.
It is differentiated into true roots, stem and leaves. Vascular tissue is well developed in these parts of the plant. The sporophyte bears the sporangia. Sporangia are subtended by leaf-like appendages called sporophylls. 

Formation of Spores: The spore mother cells in the sporangia undergo reduction division to produce spores.

Germination of Spores: Spores germinate to produce the gametophyte.

Gametophyte: Gametophyte is small but multicellular. It is free-living and usually photosynthetic. It is called prothallus. It bears antheridia and archegonia which produce male and female gametes. Transfer of male gamete takes place through pollen tube and then fertilization takes place. 

Ans. Option ‘b’ is the correct option, i.e. both will die.
Symbiosis: This is defined as a relationship between two organisms in which both the organisms get benefit from each other. There can be many examples of symbiotic relationship in which removal of one may not result in death of another partner. For example; in case of symbiotic relationship between a bird and a buffalo, the worms and insects on buffalo’s back are not the only source of food for the bird. Similarly, there can
be some other ways for the buffalo to get rid of those pests.
But in case of lichen; both the fungal and algal components depend on each other for their basic needs. In this case, alga is the only source of food for the fungal component. 
Similarly, fungus is the only source of water and minerals for the alga. They have no alternative means to fulfill their need and hence in case of removal of any one partner, another partner would die. 
 
Since it is a relationship of mutual benefit hence it will still be called symbiosis. 

In angiosperms; one of the male gamete fuses with the female gamete. Additionally, another male gamete fuses with the secondary nucleus. Fusion between male and female gametes results in formation of the zygote. Apart from that, fusion between another male gamete and the secondary nucleus results in formation of the primary endosperm nucleus (PEN). Since, two instances of fusion of nuclei take place hence it is called double fertilization. Two following figure shows double fertilization:  

(a) Liverwort 

(b) Funaria, Gametophyte and sporophyte 

(c) Alternation of generation in Angiosperm 

Algae are classified into three main classes – Chlorophyceae, Phaeophyceae, and Rhodophyceae. These divisions are based on the following factors:

(a) Major photosynthetic pigments present

(b) Form of stored food

(c) Cell wall composition

(d) Number of flagella and position of insertion

Class I – Chlorophyceae

Common name – Green algae

Major pigments – Chlorophylls a and b

Stored food – Starch

Cell wall composition – Cellulose

Flagella number and position – 2-8; equal and apical

Class II – Phaeophyceae

Common name– Brown algae

Major pigments – Chlorophylls a and c, and fucoxanthin

Stored food – Mannitol and laminarin

Cell wall composition – Cellulose and algin

Flagella number and position – 2; unequal and lateral

Class III­ – Rhodophyceae

Common name – Red algae

Major pigments – Chlorophylls a and d, and phycoerythrin

Stored food –­ Floridean starch

Cell wall – Cellulose, pectin, and polysulphate esters

Flagella number – Absent

Liverwort – In liverworts, the main plant-body is haploid (gametophytic). It bears the male and female sex organs which produce gametes. These gametes fuse to form a zygote. The zygote develops on the gametophytic plant-body to form a sporophyte. The sporophyte is differentiated into the foot, seta, and capsule. Many haploid spores are produced as a result of the reduction division taking place inside the capsule.

Moss – In mosses, the primary protonema (developed in the first stage) develops into the secondary protonema. Both these stages are haploid or gametophytic. The secondary protonema bears the sex organs which produce gametes. These gametes fuse to form a zygote. The zygote develops into a sporophyte. Many spores are formed as a result of the reduction division taking place in the capsule of this sporophyte.

Fern – In ferns, the main plant-body is sporophytic. Its leaves are known as sporophylls and these bear the sporangia. Reduction division takes place in these sporangia, thereby producing many spores.

Gymnosperm – In gymnosperms, the main plant-body is sporophytic. They bear two types of leaves – microsporophylls and megasporophylls. Reduction division takes place in the microsporangia present on the microsporophylls (producing pollen grains) and on the megasporangia present on the megasporophylls (producing megaspores).

Angiosperm – In angiosperms, the main plant-body is sporophytic and bears flowers. The male sex organ in the flower is the stamen, while the female sex organ is the pistil. Reduction division takes place in the anthers of the stamen (producing haploid pollen grains) and in the ovary of the pistil (producing eggs).

Archegonium is the female sex organ that produces the female gamete or egg. It is present in the life cycles of bryophytes, pteridophytes, and gymnosperms.

Life cycle of a fern (Dryopteris)

Dryopteris is a common fern with pinnately-compound leaves. The main plant-body is sporophytic. Many sporangia are borne on the lower surfaces of its mature leaves. Each sporangium has spore mother cells which undergo meiosis to produce haploid spores. On maturing, these spores dehisce and germinate to give rise to a heart-shaped gametophyte called prothallus.The prothallus bears the male and female sex organs called antheridia and archegonia respectively. The antheridia produce sperms that swim in water to reach the archegonia. The egg is produced by the archegonia. As a result of fertilisation, a zygote is formed. The zygote forms an embryo, which in turn develops into a new sporophyte. The young plant comes out of the archegonium

(a) Protonemal cell of a moss – Haploid

(b) Primary endosperm nucleus in a dicot – Triploid

(c) Leaf cell of a moss – Haploid

(d) Prothallus of a fern – Haploid

(e) Gemma cell in Marchantia – Haploid

(f) Meristem cell of a monocot – Diploid

(g) Ovum of a liverwort – Haploid

(h) Zygote of a fern – Diploid

Economic importance of algae

Algae have diverse economic uses. They perform half of the total carbon dioxide-fixation on earth by photosynthesis, acting as the primary producers in aquatic habitats.

(a) Food source: Many species of marine algae such as Porphyra, Sargassum, and Laminaria are edible. Chlorella and Spirulina are rich in proteins. Thus, they are used as food supplements.

(b) Commercial importance: Agar is used in the preparation of jellies and ice-cream. It is obtained from Gelidium and Gracilaria. Carrageenin is used as an emulsifier in chocolates, paints, and toothpastes. It is obtained from the red algae.

(c) Medicines: Many red algae such as Corallina are used in treating worm infections.

Economic importance of gymnosperms

(a) Construction purposes: Many conifers such as pine, cedar, etc., are sources of the soft wood used in construction and packing.

(b) Medicinal uses: An anticancer drug Taxol is obtained from Taxus. Many species of Ephedra produce ephedrine, which can be used in the treatment of asthma and bronchitis.

(c) Food source: The seeds of Pinus gerardiana (known as chilgoza) are edible.

(d) Source of resins: Resins are used commercially for manufacturing sealing waxes and water-proof paints. A type of resin known as turpentine is obtained from various species of Pinus.

Gymnosperms and angiosperms are seed-producing plants with diplontic life cycles.

In gymnosperms, the sporophylls are aggregated to form compact cones. The microsporophylls are broad and are not distinguished into filaments and anthers. The megasporophylls are woody and lack the ovary, style, and stigma, because of which the ovules lie exposed. The female gametophyte consists of archegonia. The fertilisation process involves the fusion of a male gamete with the female gamete. Their endosperm is haploid. The produced seeds are naked as there is no fruit formation.

Angiosperms are also known as flowering plants. They have sporophylls that aggregate to form flowers with the perianth. The microsporophylls consist of stamens containing pollen sacs. These sacs bear the male gametes called pollen grains. The megasporophylls are delicate and rolled, forming carpels that contain the ovary, style, and stigma. The ovules are present inside the ovary. The archegonium is replaced by an egg apparatus. Two male gametes enter the egg apparatus at the time of fertilisation. One male gamete fertilises the egg and the other fuses with the diploid secondary nucleus to form an endosperm. The resulting endosperm is thus triploid. In addition, in angiosperms, the development of seeds takes place inside the fruits.

Heterospory is a phenomenon in which two kinds of spores are borne by the same plant. These spores differ in size. The smaller one is known as microspore and the larger one is known as megaspore. The microspore germinates to form the male gametophyte and the megaspore germinates to form the female gametophyte. The male gametophyte releases the male gametes and these reach the female gametophyte to fuse with the egg. The development of the zygote takes place inside the female gametophyte.

This retention and germination of the megaspore within the megasporangium ensures proper development of the zygote. The zygote develops into the future sporophyte. The evolution of the seed habit is related to the retention of the megaspore.

Heterospory is thus considered an important step in evolution as it is a precursor to the seed habit.

Heterospory evolved first in pteridophytes such as Selaginella and Salvinia.

(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.

(i) Red algae and brown algae

(ii) Liverworts and moss

(iii) Homosporous and heterosporous pteridophyte

(iv) Syngamy and triple fusion

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

Match the followings (column I with column II)

Answer 11:

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.

Bryophytes need water for at least one stage of their life cycle. This is similar to Amphibians which also need water to lay eggs and their tadpoles develop in water. Hence, bryophytes are called the amphibians of the plant kingdom.

Structure	Pteridophyte	Gymnosperm	Angiosperm
Main reproductive part	Gametophyte bears antheridia and archegonia	Microsporophylls andmegasporophylls represent the gametophyte.	Flower bear antheridium an gynoecium.
Male reproductive part	Antheridia produce the malegamete.	The male cone is highlyreduced in size.	Antheridia are composed of an anther and a slender stalk. Anther produces the pollen grains, i.e. male gametes.
Female reproductive part	Archegonia produce the female gamete.	The megasporophyll is large in size and is easily apparent as the female cone.	The gynoecium contains the ovary, style and stigma. Fertilised egg develops inside the ovary and eventually seeds are produced.

Heterospory involves formation of two types of spores. Microspores are smaller in size and megaspores are much larger in size. In some Pteridophytes, the microspores and megaspore germinate to give rise to male and female gametophytes respectively. Finally, the zygote develops inside the female gametophyte. From evolutionary perspective, this is a precursor of seed habit in higher plants. Seeds have  enabled gymnosperms and angiosperms to tide over long p e r i o d s  of unfavourable conditions. Seeds have also enabled them to spread to wider geographical area through seed dispersal. It has indeed helped these plants in further evolution.
 

In case of Selaginella, the development of zygote into embryo takes place within the female gametophyte. This female gametophyte is retained on the parent plant for variable periods .  This is considered as a precursor of seed habit because advanced version of this phenomenon is seen in higher plants; like gymnosperms and angiosperms.  

But unlike seeds in higher plants; the embryo in Selaginella needs to quickly develop to begin the new generation. However, there could be temporary suspension of embryo growth; which is similar to seed dormancy in higher plants. 
 
 

Cycas is considered as a living fossil because it is the only living species in the family Cycadaceae. All other species of this family are now extinct. This plant is often considered as the plant of the Old World; which means it is found only at those places which can be associated with some of the oldest rocks in the world. Due to these reasons; it is called as the ‘relic of the past’. Moreover, Cycas shows more resemblance with Pteridophytes than Gymnosperms. This shows phylogenetic relationship between Pteridophytes and Gymnosperms. Some of the characters of Cycas which indicate towards this are as follows: 
(a) Seeds are shed when the embryo is still mature. In other gymnosperms; seeds are shed only when the embryo is mature.
(b) The megasporophyllus appears like leaf.
(c) In spite of the presence of pollen tubes, male gametes are flagellate.
(d) Leaf base is persistent.
(e) Circinate ptysix; which is similar as in Pteridophytes. 

Heterospory in pteridophytes leads to development of two different kinds of spores, i.e. microspores and megaspores. This is similar to higher plants in which male gametes are much smaller than female gametes. Another important feature is in situ development of embryo; which is similar to development of embryo in higher plants. Development of embryo inside the female gametophyte enables it to take nutrition from the female 
gametophyte. This is beneficial for proper development of embryo and give certain survival bene fits to the embryo. Thus, it can be said that heterospory in pteridophytes is a precursor to seed habit in gymnosperm.

. Fern (pteridophytes) exhibit haplo-diplontic condition. In this condition; both the gametophytic and sporophytic phases are multicellular. The diploid sporophyte is represented by a dominant, independent, photosynthetic, vascular plant body. The haploid gametophyte is also independent but it lives for a shorter duration than the sporophyte generation. The following figure shows the life cycle of plant showing haplodiplontic
condition.
 

Nature of Fern Prothallus:
The prothallus represents the haploid gametophytic generation. This is multicellular, ndependent, photosynthetic form which lives for a short duration. The prothallus needs cool, damp and shady place to grow. Due to its requirement of water for fertilization, pteridophytes are restricted to narrow geographical regions. 

Male gametophyte of pteridophyte	Male gametophyte of gymnosperm
(i) Distinct male gametophyte may not be present.	(i) Distinct male gametophyte is always present.
(ii) Antheridium is present.	(ii) Antheridium is absent.
(iii) Male gametes are flagellated.	(iii) Male gametes may or may not be flagellated
(iv) Male gametes need water as a medium to swim up to the female gamete.	(iv) Male gametes reach the female gamete through pollen tube. Water is not required for this purpose.

Mycorrhiza: It is a symbiotic association between a fungus and the roots of a vascular plant. Mycorrhiza is found in some genus of gymnosperms; like Pinus.
Coralloid Roots: These roots too show symbiotic association but in this case, the association is with nitrogen fixing cyanobacteria. Many nodules are formed in the roots giving them coralloid appearance. Examples are Cycas and plants of leguminoceae.
 

Mannitol is the reserve food material in Phaeophyceae or Brown Algae.
 

(a) Volvox, Spirogyra
(b) Fucus
(c) Polysiphonia
 

Rhizome

(a) Ectocarpus, Polysiphonia
(b) Fucus

Antheridium, Archegonium

(c) Monera

(c) Anisogamy 

Size of gametes is dissimilar and hence term ‘Anisogamy’ is used. 

Ans. (c) Phaeophyceae

Ans. (d) Bryophytes
Plants from monocots and gymnosperms do not need water for fertilization. Byrophytes and pteridophytes need water for fertilization. But
pteridophytes have true roots. Hence, ‘d’ is the correct option. 

Ans. (c) A gametophyte free living structure formed in pteridophytes

Ans. (d) Gymnosperms
Cones are salient features of gymnosperms. Moreover, gymnosperms are well adapted to extreme conditions. 

Ans. (b) 7 cells and 8 nuclei
The seven cells are; one egg cell, two synergids, three antipodal cells and one secondary nucleus. The secondary nucleus contains two nuclei; while the other cells contain one nucleus each.

Ans. (c) 54
Endosperm is formed after fusion between a haploid male gamete and diploid secondary nucleus. Thus, endosperm has triploid nucleus; which will have three times the number of chromosomes as in a haploid nucleus. 

Ans. (a) Haploid and is found in mosses
 

Ans. (d) Gymnosperm
Redwood trees is a Gymnosperm which have earned many sobriquets; like tallest tree, oldest tree, largest by trunk volume, etc. 
 

In bryophytes, the dominant phase is represented by  gametophytic plant. The gametophyte is independent, photosynthetic, thalloid phase. Antheridia and archegonia are formed on the gametophye. These organs are multicellular. These organs bear the respective gametes, viz. male and female. The antheridium produces biflagellate antherozoids. The archegonium is flask-shaped. It produces a single egg.

Transfer of antherozoids to the archegonium take place through water. Flagella in the a ntherozoids facilitate motility. Zygote is formed after fertilization. But the zygote does not undergo meiosis immediately after fertilization. It develops into a multicellular body called sporophyte.
The sporophyte in bryophytes is much smaller and is not independent but attached to the gametophyte. It gets nutrition from the gametophyte. It is clear that the gametophyte is dominant phase in the life cycle of  a bryophyte in every aspect. Gametophyte is  independent and photosynthetic. It is much larger in size compared to the sporophyte.  
On the other hand, the sporophyte is not free-living but remains attached to the gametophyte so that it can get nutrition. 

Both pteridophyte and bryophyte show haplo-diplontic life cycle. While the diploid phase is not independent in bryophytes, it is independent in pteridophytes. Moreover, the  sporophyte is more conspicuous in pteridophytes than in bryophytes. Sporophyte is the dominant phase in life cycle of pteridophyte.
The given figure shows the haplo-diplontic life cycle. 

Sporophyte: The sporophyte is well developed plant body.
It is differentiated into true roots, stem and leaves. Vascular tissue is well developed in these parts of the plant. The sporophyte bears the sporangia. Sporangia are subtended by leaf-like appendages called sporophylls. 

Formation of Spores: The spore mother cells in the sporangia undergo reduction division to produce spores.

Germination of Spores: Spores germinate to produce the gametophyte.

Gametophyte: Gametophyte is small but multicellular. It is free-living and usually photosynthetic. It is called prothallus. It bears antheridia and archegonia which produce male and female gametes. Transfer of male gamete takes place through pollen tube and then fertilization takes place. 

Both pteridophyte and bryophyte show haplo-diplontic life cycle. While the diploid phase is not independent in bryophytes, it is independent in pteridophytes. Moreover, the  sporophyte is more conspicuous in pteridophytes than in bryophytes. Sporophyte is the dominant phase in life cycle of pteridophyte.
The given figure shows the haplo-diplontic life cycle. 

Sporophyte: The sporophyte is well developed plant body.
It is differentiated into true roots, stem and leaves. Vascular tissue is well developed in these parts of the plant. The sporophyte bears the sporangia. Sporangia are subtended by leaf-like appendages called sporophylls. 

Formation of Spores: The spore mother cells in the sporangia undergo reduction division to produce spores.

Germination of Spores: Spores germinate to produce the gametophyte.

Gametophyte: Gametophyte is small but multicellular. It is free-living and usually photosynthetic. It is called prothallus. It bears antheridia and archegonia which produce male and female gametes. Transfer of male gamete takes place through pollen tube and then fertilization takes place. 

Ans. Option ‘b’ is the correct option, i.e. both will die.
Symbiosis: This is defined as a relationship between two organisms in which both the organisms get benefit from each other. There can be many examples of symbiotic relationship in which removal of one may not result in death of another partner. For example; in case of symbiotic relationship between a bird and a buffalo, the worms and insects on buffalo’s back are not the only source of food for the bird. Similarly, there can
be some other ways for the buffalo to get rid of those pests.
But in case of lichen; both the fungal and algal components depend on each other for their basic needs. In this case, alga is the only source of food for the fungal component. 
Similarly, fungus is the only source of water and minerals for the alga. They have no alternative means to fulfill their need and hence in case of removal of any one partner, another partner would die. 
 
Since it is a relationship of mutual benefit hence it will still be called symbiosis. 

In angiosperms; one of the male gamete fuses with the female gamete. Additionally, another male gamete fuses with the secondary nucleus. Fusion between male and female gametes results in formation of the zygote. Apart from that, fusion between another male gamete and the secondary nucleus results in formation of the primary endosperm nucleus (PEN). Since, two instances of fusion of nuclei take place hence it is called double fertilization. Two following figure shows double fertilization:  

(a) Liverwort 

(b) Funaria, Gametophyte and sporophyte 

(c) Alternation of generation in Angiosperm