GSEB Class 11 Biology Solutions Chapter 3 Plant Kingdom

Question 1. What is the basis of the classification of algae?
Answer: Algae are categorized by their color, which depends on the specific pigments present or absent that provide its hue.

• Chlorophyceae → green algae or blue-green algae because of pigments chlorophyll a and b
• Phaeophyceae → brown algae due to pigments chlorophyll a and c, and fucoxanthin.
• Rhodophyceae → Red algae because of phycoerythrin (red colour) and chlorophyll a and d.

Exam Tip: When classifying organisms based on a specific characteristic, always list the key feature and then provide examples for each category to illustrate the differences clearly.

Question 2. When and where does reproduction take place in the life cycle of a liverwort, a moss, a fern, a gymnosperm, and an angiosperm?
Answer:The plant body of a liverwort is thalloid, like Marchantia. Asexual reproduction in liverworts happens through thalli fragmentation or by developing specialized structures called gemmae. The main stage of a moss's life cycle is the gametophyte, comprising two stages: protonema and leafy stage.
Mosses reproduce vegetatively by fragmentation and budding within the secondary protonema. In sexual reproduction, antheridia and archegonia (sex organs) form at the tip of the leafy shoots. After fertilization, the zygote grows into a sporophyte, made up of a foot, seta, and capsule. The capsule holds spores, which are created after meiotic division. Mosses also possess a complex system for spore dispersal. Funaria, Polytrichum, and Sphagnum are typical moss examples.
Pteridophyta covers horsetails and ferns. Most pteridophytes produce similar types of spores, making them homosporous plants. Female gametophytes in these plants stay on the parent sporophyte for different lengths of time. Zygotes develop into young embryos inside the female gametophytes. This occurrence is seen as a key evolutionary step towards the seed habit. Pteridophyta is further divided into four classes: psilopsida, lycopsida, sphenopsida, and pteropsida.
Gymnosperms are heterosporous; they create haploid microspores and megaspores. Both spore types form inside sporangia, carried on sporophylls arranged spirally along an axis to create loose or dense strobili or cones. Strobili with microsporophylls and microsporangia are known as microsporangia or male strobili. Microspores evolve into a very small male gametophytic generation, restricted to just a few cells. This smaller gametophyte is named a pollen-grain. Pollen grains develop within the microsporangia. Cones having megasporophylls with ovules or megasporangia are called microsporangia or female strobili. Male or female cones or strobili can be on the same tree (Pinus) or on distinct trees (Cycas). Ovules are carried on megasporophylls, which may be released to form female cones. The megaspore mother cell undergoes mitotic division to produce four megaspores. One megaspore, held inside the megasporangium (nucellus), grows into a multicellular female gametophyte that holds two or more archegonia or female sex organs. This multicellular female gametophyte also stays within the megasporangium.
Angiosperms are flowering plants where seeds are held within fruits. The male reproductive part in a flower is the stamen, each made of a thin filament with an anther at its end. Anthers generate pollen grains after meiosis. The female reproductive part is the pistil or carpel. A pistil contains an ovary that encloses one to many ovules. Inside the ovules are greatly reduced female gametophytes, called embryo-sacs. Embryo-sacs are haploid. Each embryo sac contains a 3-celled egg structure—one egg cell and two synergids, three antipodal cells, and two polar nuclei. These polar nuclei ultimately combine to form a diploid secondary nucleus. After leaving the anthers, pollen grains travel to the pistil's stigma via wind or other methods. This process is known as pollination.In simple words: Reproduction in different plant groups occurs in various ways and places. Liverworts use fragmentation and gemmae. Mosses use fragmentation, budding, and sexual reproduction with antheridia and archegonia on leafy shoots. Ferns have sporangia producing spores. Gymnosperms use cones with microspores and megaspores, leading to pollen and ovules. Angiosperms use flowers, where stamens produce pollen and pistils contain ovules, leading to pollination and seed formation inside fruits.

Exam Tip: For each plant group, remember the key reproductive structures (e.g., gemmae, archegonia, sporangia, cones, flowers) and their location (e.g., thalli, leafy shoots, sporophylls, ovaries).

Question 3. Name three groups of plants that bear archegonia. Briefly describe the life cycle of any one of them.
Answer: Bryophytes, pteridophytes, and gymnosperms all possess distinct archegonia.
The life cycle of gymnosperms:
Gymnosperms are heterosporous plants. They create haploid microspores and megaspores. Both types of spores form inside sporangia, which are carried on sporophylls. These sporophylls are organized spirally along a central axis to form loose or dense strobili (cones). Strobili that have microsporophylls and microsporangia are named microsporangia or male strobili. Microspores mature into a male gametophyte generation, which is significantly smaller and includes only a few cells. This smaller gametophyte is known as a pollen grain. Pollen grain development occurs within the microsporangia.
Cones that bear megasporophylls with ovules or megasporangia are called microsporangia or female strobili. Male or female cones or strobili can be found on the same tree (like Pinus). However, in Cycas, male cones and megasporophylls appear on different trees. A megaspore mother cell develops from one of the nucellus cells. The nucellus is protected by outer layers, and this entire complex structure is known as an ovule. Ovules are carried on megasporophylls, which may be released to form female cones. The megaspore mother cell undergoes mitotic division to produce four megaspores. One megaspore, held inside the megasporangium (nucellus), grows into a multicellular female gametophyte that holds two or more archegonia or female sex organs. This multicellular female gametophyte also stays within the megasporangium.In simple words: Bryophytes, pteridophytes, and gymnosperms all have archegonia. For gymnosperms, they make two kinds of spores, micro and mega, in cones. Microspores become pollen grains, and megaspores become female gametophytes inside ovules, which are protected. Some trees have both male and female cones, while others have them on separate trees.

Exam Tip: When asked to describe a life cycle, always mention the spore types, the structures where they are produced, and how they develop into gametophytes and sporophytes, along with any relevant examples.

Question 4. Mention the ploidy of the following: protonemal cell of a moss, primary endosperm nucleus in dicot; leaf ceil of a moss; prothallus cell of a fern; gemma cell in Marchantia; meristem ceil of monocot; ovum of a liverwort, and zygote of a fern.
Answer:(1) Protonemal cell of a moss: \(n\) (haploid). The initial stage is the protonema stage, which directly grows from a spore. This stage is creeping, green, branched, and often filamentous.
(2) Primary endosperm nucleus in dicot: \(3n\) (triploid). Pollen tubes go into the embryo-sac, where the two male gametes are released. One male gamete combines with the egg cell to create a zygote (syngamy). The other male gamete merges with the diploid secondary nucleus or two haploid polar nuclei (triple fusion) to form the triploid primary endosperm nucleus (PEN). The zygote then grows into an embryo (with one or two cotyledons), and the PEN transforms into endosperm, which gives food to the growing embryo.
(3) Leaf cell of a moss: \(n\) (haploid). The second phase is the leafy stage, which grows from the secondary protonema as a side bud. These cells have upright, thin stems carrying spirally placed leaves. They connect to the soil using multicellular, branched rhizoids. This phase also holds the sex organs.
(4) Prothallus cell of a fern: \(n\) (haploid). Sporangia generate spores through meiosis in spore mother cells. These spores sprout, leading to small, often unseen, yet multicellular, free-living, mostly photosynthetic thalloid gametophytes, also known as prothallus. These gametophytes need cool, moist, shady areas to thrive. The gametophyte contains male and female sex organs, called antheridia and archegonia, respectively.
(5) Gemma cell in Marchantia: \(n\) (haploid). Gemmae are green, multicellular asexual buds that grow in small cup-shaped structures on the thalli, called gemma cups. These gemmae detach from the parent plant and sprout to create new individuals. During sexual reproduction, male and female sex organs appear on the same or different thalli. The sporophyte develops into a foot, seta, and capsule (e.g., Marchantid). After meiosis, spores form within the capsule. These spores then sprout to create free-living gametophytes.
(6) Meristem cell of monocot: \(2n\) (diploid). Meristem tissue is a simple tissue, composed of young (undifferentiated) cells. The cells are small and roughly spherical. Their cell wall is thin. Intercellular spaces are very small or might be absent. Crystals and other cell inclusions are not present. Metabolic activities within these cells are quite high. The cell has the ability to undergo repeated divisions.
(7) Ovum of a liverwort: \(n\) (haploid). Asexual reproduction in liverworts happens through fragmentation or by forming special structures called gemmae. Gemmae are green, multicellular asexual buds that grow in small cup-like structures on the thallus, named gemma cups. These gemmae separate from the parent body and sprout to create new individuals. During sexual reproduction, male and female sex organs appear on either the same or different thalli. The sporophyte differentiates into a foot, seta, and capsule. After meiosis, spores are formed within the capsule. These spores then sprout to become free-living gametophytes.
(8) Zygote of a fern: \(2n\) (diploid). The joining of a male gamete with the egg cell inside the archegonium results in zygote formation. The zygote then produces a multicellular, well-developed sporophyte, which is the main phase of pteridophytes. In most pteridophytes, all spores are of similar types; such plants are known as homosporous. Megaspores and microspores sprout and develop into female and male gametophytes, respectively. Female gametophytes in these plants remain on the parent sporophyte for differing durations. The growth of zygotes into young embryos happens inside the female gametophytes. This event is viewed as a crucial step in evolution, leading towards the seed habit.In simple words: The ploidy (number of chromosome sets) for each part is: moss protonema, moss leaf cell, fern prothallus cell, Marchantia gemma cell, and liverwort ovum are all haploid (\(n\)). The dicot primary endosperm nucleus is triploid (\(3n\)). The monocot meristem cell and fern zygote are diploid (\(2n\)).

Exam Tip: Remember that gametophytic stages are typically haploid (\(n\)), while sporophytic stages and zygotes are diploid (\(2n\)). The primary endosperm nucleus in angiosperms is a unique triploid (\(3n\)) structure.

Question 5. Write a note on the economic importance of algae and gymnosperms.
Answer:Economic importance of Algae:
Algae benefit people in many ways. At least half of all carbon dioxide absorbed on Earth is done by algae via photosynthesis. Because they perform photosynthesis, they raise the amount of dissolved oxygen nearby. They are extremely vital as main producers of energy-filled compounds, forming the base of food chains for all water animals.
Many types of Porphyra, Laminaria, and Sargassum are among the 70 marine algal species eaten as food. Some marine brown and red algae generate large quantities of hydrocolloids (water-retaining substances), such as algin (from brown algae) and carrageen (from red algae), which are used commercially. Agar, a commercial substance derived from Gelidium and Gracilaria, helps grow microbes and is used in ice creams and jellies. Chlorella and Spirulina are single-celled algae, full of proteins, and serve as food supplements, even for astronauts.
Economic Importance of Gymnosperms:
Gymnosperm plants find extensive use as ornamentals. Conifers frequently appear in formal gardens and are suitable for bonsai. Yews and junipers, as low-growing plants, are often grown for ground cover. Conifers make good windbreaks, especially evergreen types. Turpentine and resin come from conifer resins. Copal, a hardened resin from a kauri tree, is employed to produce paints and varnishes. Balsam and dammar resin are utilized for making mounting media for microscope slides. Resins also have medicinal benefits.
Fossilized conifer resin is used to create amber. Commercially valuable oils are extracted from conifers like junipers, pines, hemlock, fir, spruces, and arborvitae. These oils function as air fresheners, disinfectants, and scents in soaps and cosmetics. Seeds frequently serve as food sources. Pine seeds are a treat, eaten plain or used to decorate baked goods. Ginkgo and cycad seeds might be toxic unless made safe. Juniper "berries" are employed as flavouring. Most plywood originates from gymnosperms.In simple words: Algae are important because they produce oxygen, form the base of aquatic food chains, and give us food items like seaweeds, agar, and protein supplements. Gymnosperms are important for ornamental use, windbreaks, and provide turpentine, resins, oils for various products, and some seeds for food.

Exam Tip: When discussing economic importance, categorize the benefits into ecological (e.g., oxygen production, food chain base) and commercial (e.g., food, industrial products, medicinal uses) categories for a complete answer.

Question 6. Both gymnosperms and angiosperms bear seeds, then why are they classified separately?
Answer: Gymnosperms and angiosperms are categorized separately because gymnosperm sporophylls gather to form cones, while angiosperm sporophylls gather to form a flower. In gymnosperms, a seed grows openly on the megasporophyll, and no fruit develops. However, in angiosperms, seeds develop inside the ovary, which ripens into a fruit. Gymnosperm ovules are visible on the megasporophylls, whereas angiosperm ovules are contained within the ovary, thus hidden. A gymnosperm ovule has three layers of integuments with a wide micropyle, while an angiosperm ovule has one or two thin integuments with a narrow micropyle. In gymnosperms, pollen grains directly access the ovule and settle on the nucleus, whereas in angiosperms, pollen grains arrive at the stigma, which is the specific receiving part.In simple words: They are separate because gymnosperm seeds are exposed on cones and never form fruits, while angiosperm seeds are enclosed within an ovary that develops into a fruit. Also, their ovule structures and how pollen reaches them are different.

Exam Tip: Focus on the fundamental differences in reproductive structures and seed protection (exposed vs. enclosed in an ovary/fruit) when differentiating between gymnosperms and angiosperms.

Question 7. What is heterospory? Briefly comment on its significance. Give two examples.
Answer: Pteridophytes create two types of spores. This occurrence is known as heterospory. Microspores are small male gametophytes, while megaspores are larger female gametophytes. The growth of zygotes into embryos happens inside the female gametophytes. This process serves as a step towards the seed habit, viewed as a crucial point in plant evolution. Examples include Selaginella and Salvinia.In simple words: Heterospory means producing two different sizes of spores: small ones (microspores) that become male gametophytes, and large ones (megaspores) that become female gametophytes. This is important because it's a step towards how seeds develop. Selaginella and Salvinia are examples.

Exam Tip: When defining biological terms like heterospory, always provide a clear definition, explain its significance (e.g., evolutionary implications), and give relevant examples.

Question 8. Explain briefly the following terms with a suitable example:
(1) Protoneuia
(2) Antheridium
(3) Archegonium
(4) Diplontic
(5) Sporophyll
(6) Isogamy
Answer:(1) Protonema: The main stage in a moss's life cycle is the gametophyte, which has two stages. The initial stage is the protonema, growing directly from a spore. It is a creeping, green, branched, and often filamentous stage.
(2) Antheridium: Bryophyte sex organs are multicellular. The male sex organ is known as antheridium.
(3) Archegonium: The female sex organ is named archegonium.
(4) Diplontic: This type involves the diploid sporophyte as the main, photosynthetic, independent phase of the plant. The gametophytic phase is shown by single to few-celled haploid gametophytes. This life cycle is termed diplontic. All plants that produce seeds, such as gymnosperms and angiosperms, follow this growth pattern.
(5) Sporophyll: The sporophyte holds sporangia that are supported by leaf-like structures called sporophylls.
(6) Isogamy: Sexual reproduction happens when two gametes fuse. These gametes might be flagellated and similar in size (like in Chlamydomonas) or non-flagellated (not moving) but still similar in size (like in Spirogyra). This type of reproduction is called isogamous.In simple words: Protonema is the early, filamentous stage of a moss. Antheridium is the male sex organ, and archegonium is the female sex organ in lower plants. Diplontic describes a life cycle where the diploid stage is dominant, as in humans and seed plants. A sporophyll is a leaf that carries spores. Isogamy is when two fusing gametes are identical in size and shape.

Exam Tip: For definitions, always state what the term is, what it does or represents, and provide a clear example if applicable. Ensure your examples are specific and correct.

Question 9. Differentiate between the following:
1. Red algae and Brown algae
2. Liverworts and Moss
3. Homosporous and Heterosporous pteridophyte
4. Syngamy and Triple fusion.
Answer:1. Red algae and Brown algae:
Red Algae:
1. Mostly marine, they include various seaweeds. A small number, however, live in freshwater (e.g., Batrachospermum). 2. Their size varies from microscopic to about half a meter. Their plant body can be unicellular (e.g., Porphyridium), filamentous (e.g., Steriocystis), or a sheet of cells (e.g., Porphyra Chondrus). 3. Their cell walls contain sulfated mucopolysaccharides, known as Phycocolloids, along with cellulose and pectic substances. Key hydrocolloids from red algae include agar, carrageenin, and porphyrin. 4. Some red algae gather calcium carbonate from seawater, which they deposit on their walls. They look like coral and are named coralline algae (e.g., Corallina). 5. The stored food in red algae is Floridian starch, which is somewhat like glycogen. 6. Red algae do not have flagellated or motile cells. 7. Some red algae show an alternation of haploid and diploid generations during their life cycle. 8. Sexual reproduction happens via various non-motile spores such as neutral spores, monospores, carpospores, and tetraspores.
Brown Algae:
1. These are all marine plants, mostly found in colder seas. Sargassum is an exception, growing in warmer waters. 2. Unlike red or green algae, brown algae do not have a unicellular form. Some are the largest sea plants, reaching 40-60 meters in length (e.g., Macrocystis). They can be branched, filamentous (e.g., Ectocarpus), or flat ribbon-shaped (e.g., Sargassum, Laminaria, Fucus). 3. The plant structure of bigger forms often separates into a holdfast, stipe, and lamina. 4. Brown algae are typically found attached by their holdfast. A few, like Sargassum and Fucus, float freely. 5. Their reserve food consists of carbohydrates like laminarin and lipid. 6. Vegetative reproduction happens through fragmentation and special propagules called nests of cells. 7. An alternation of haploid and diploid generations takes place in some algae during their life cycles. In some types, both generations appear similar in structure. 8. Sexual reproduction ranges from isogamy, anisogamy, to oogamy. In isogamy and anisogamy, both gametes are motile and have heterokont flagella.
2. Liverworts and Moss:
Liverworts:
1. They show dorsiventral symmetry. 2. They are usually thalloid, seldom leafy, with two-way branching. 3. Their rhizoids are single-celled. 4. Scales are frequently found. 5. No filamentous stage exists. 6. The sporophyte has very little tissue that performs photosynthesis. 7. A central columella is not present inside the capsule. 8. Elaters are found in the capsule to help spread spores, but peristome teeth are missing.
Mosses:
1. They have radial symmetry. 2. They are typically leafy, with side branching. 3. Their rhizoids are multicellular. 4. Scales are not present. 5. A filamentous protonema stage is always found. 6. The sporophyte has plenty of photosynthetic capacity. 7. A central columella is found inside the capsule. 8. Elaters are not present, but peristome teeth are in the capsule to help with spore dispersal.
3. Homosporous and Heterosporous pteridophyte:
Homosporous:
After formation, the zygote creates a multicellular, well-developed sporophyte that becomes the main phase of pteridophytes. In most pteridophytes, all spores are of similar types; such plants are named homosporous.
Heterosporous:
Genera such as Selaginella and Salvinia, which generate two kinds of spores—macro (large) and micro (small)—are known as heterosporous.
4. Syngamy and Triple fusion:
Syngamy:
Pollen tubes go into the embryo-sac, releasing two male gametes. One male gamete then combines with the egg cell to form a zygote (Syngamy).
Triple fusion:
The other male gamete merges with the diploid secondary nucleus, or two haploid polar nuclei (triple fusion), to generate the triploid primary endosperm nucleus (PEN).In simple words: This question asks us to compare four pairs of biological terms: Red algae vs. Brown algae, Liverworts vs. Mosses, Homosporous vs. Heterosporous pteridophytes, and Syngamy vs. Triple fusion. Each comparison highlights key differences in their characteristics, life cycles, or reproductive processes.

Exam Tip: When asked to differentiate, create clear distinctions point-by-point for each item. Use contrasting terms and specific biological details to show a thorough understanding.

Question 10. How would you distinguish monocots from dicots?
Answer:

Exam Tip: Use a comparative table format to clearly highlight the distinguishing features between monocots and dicots, making it easy for the examiner to understand your answer.

Question 11. Match the following Column I with Column II
Answer:a. Chlamydomonas - iii. Algae
b. Cycas - iv. Gymnosperm
c. Selaginella - ii. Pteridophyte
d. Sphagnum - i. Moss
In simple words: Chlamydomonas is a type of Algae. Cycas is a Gymnosperm. Selaginella is a Pteridophyte. Sphagnum is a Moss.

Exam Tip: For matching questions, it's helpful to write out the pairs clearly. Double-check each match to ensure it's biologically accurate.

Question 12. Describe the important characteristics of gymnosperms.
Answer: Key features of gymnosperms include:

• Gymnosperms are plants where ovules are not covered by an ovary wall and stay exposed, both before and after fertilization.
• They consist of medium-sized to tall trees and shrubs.
• Roots are typically taproots; some kinds have a fungal link as mycorrhiza (Pinus) in their roots, while others (Cycas) contain N2-fixing cyanobacteria.
• Stems can be unbranched (Cycad) or branched (Pinus, Cedrus).
• Leaves may be simple or compound. In Cycas, pinnate leaves stay on the plant for several years.
• Gymnosperm leaves are well-suited to handle extreme temperatures, humidity, and wind.
• Conifers have needle-like leaves that lessen surface area. Their thick cuticle and sunken stomata also aid in decreasing water loss.

Exam Tip: When describing characteristics, use bullet points for clarity and include details about their reproductive structures, growth habit, root types, and leaf adaptations.