CBSE Class 11 Biology Revision Notes Chapter 3 Plant Kingdom

CBSE Class 11 Biology Revision Notes Chapter 3 explain Plant Kingdom through algae, bryophytes, pteridophytes, gymnosperms and angiosperms. For CBSE 2026 Biology, Plant Kingdom builds the classification base for plant groups, life cycles, reproduction and evolutionary trends.

Why are cyanobacteria no longer treated as algae, while Volvox, Marchantia, Selaginella, Pinus and flowering plants stay within the study of Plantae? The NCERT Class 11 Biology chapter Plant Kingdom begins with this shift in classification and shows how plant groups are arranged using structure, reproduction and evolution. Earlier systems used visible features like habit, colour and leaf shape, but modern systems consider natural affinities, evolutionary relationships, cytology and chemical characters.

The chapter then moves through algae bryophytes pteridophytes gymnosperms angiosperms in increasing complexity. Algae are mostly aquatic thalloid plants, bryophytes depend on water for fertilisation, pteridophytes introduce vascular tissues, gymnosperms form naked seeds and angiosperms enclose seeds inside fruits. This sequence helps students connect plant body organisation, dominant life cycle stage, spores, seeds and reproductive structures.

Key Takeaways

• Algal photosynthesis: Algae carry out at least half of the total carbon dioxide fixation on earth.
• Bryophyte reproduction: Bryophytes can live on soil but need water for sexual reproduction.
• Vascular milestone: Pteridophytes are the first terrestrial plants with xylem and phloem.
• Seed difference: Gymnosperm seeds remain naked, while angiosperm seeds are enclosed in fruits.

CBSE Class 11 Biology Revision Notes Chapter 3 Structure 2026

Classification Systems Used in Plant Kingdom

The NCERT Class 11 Biology chapter Plant Kingdom explains that plant classification has changed from artificial systems to phylogenetic systems. Modern classification uses evolutionary relationships instead of only external features.

Artificial systems used a few visible characters such as habit, colour, leaf number or androecium structure. Natural and phylogenetic systems use broader evidence such as anatomy, embryology, ultrastructure, phytochemistry and ancestry.

Artificial classification

Artificial classification systems use a few superficial characters. The system given by Linnaeus used features such as androecium structure.

These systems can separate closely related species because they give equal weightage to vegetative and sexual characters. Vegetative characters can also change easily due to environment.

Natural classification

Natural classification systems use natural affinities among organisms. They consider external features and internal characters.

George Bentham and Joseph Dalton Hooker gave a natural classification system for flowering plants. This system considered a wider set of characters than artificial systems.

Phylogenetic classification

Phylogenetic classification is based on evolutionary relationships. It assumes that organisms in the same taxon share a common ancestor.

Plant Kingdom class 11 notes also include numerical taxonomy, cytotaxonomy and chemotaxonomy. Numerical taxonomy uses many observable characters, cytotaxonomy uses chromosome data and chemotaxonomy uses chemical constituents.

Algae: Simple Thalloid Plants

Algae are chlorophyll-bearing, simple, thalloid, autotrophic and largely aquatic organisms. They may live in freshwater, marine water, moist stones, soil, wood or in association with fungi and animals.

Their body form ranges from colonial Volvox and filamentous Ulothrix to large marine kelps. In class 11 biology chapter 3 plant kingdom notes, algae form the first major plant group under Plantae.

Reproduction in algae

Algae reproduce by vegetative, asexual and sexual methods. Vegetative reproduction occurs by fragmentation.

Asexual reproduction usually occurs through spores, especially motile zoospores. Sexual reproduction occurs through fusion of gametes.

Isogamy, anisogamy and oogamy

Isogamy involves fusion of similar gametes. Ulothrix has flagellated similar gametes, while Spirogyra has non-motile similar gametes.

Anisogamy involves fusion of dissimilar gametes, as seen in Eudorina. Oogamy involves one large non-motile female gamete and one smaller motile male gamete, as seen in Volvox and Fucus.

Economic importance of algae

Economic importance of algae class 11 includes oxygen production, food, hydrocolloids, agar and protein supplements. Algae increase dissolved oxygen and act as primary producers in aquatic food cycles.

Porphyra, Laminaria and Sargassum are used as food. Algin comes from brown algae, carrageen comes from red algae and agar from Gelidium and Gracilaria is used in microbial culture, ice-creams and jellies.

Main Classes of Algae

NCERT divides algae into Chlorophyceae, Phaeophyceae and Rhodophyceae. The basis includes pigments, stored food, cell wall and flagellar characters.

This section is important for plant kingdom class 11 revision notes because many questions ask students to compare green, brown and red algae.

Chlorophyceae

Chlorophyceae are commonly called green algae. They contain chlorophyll a and b, which give them a grass-green colour.

Their stored food is starch and most members have pyrenoids in chloroplasts. Common examples are Chlamydomonas, Volvox, Ulothrix, Spirogyra and Chara.

Phaeophyceae

Phaeophyceae are commonly called brown algae and are mainly marine. Their colour depends on the xanthophyll pigment fucoxanthin.

They store food as laminarin or mannitol. Common examples are Ectocarpus, Dictyota, Laminaria, Sargassum and Fucus.

Rhodophyceae

Rhodophyceae are commonly called red algae because of the pigment r-phycoerythrin. Most red algae are marine and are found more in warmer areas.

They store food as floridean starch. Common examples are Polysiphonia, Porphyra, Gracilaria and Gelidium.

Bryophytes: Amphibians of the Plant Kingdom

Bryophytes are called amphibians of the plant kingdom because they live on soil but need water for sexual reproduction. They usually grow in damp, humid and shaded places.

Their plant body is more differentiated than algae but lacks true roots, stems and leaves. They have rhizoids and may show root-like, stem-like or leaf-like structures.

Main plant body of bryophytes

The main plant body of bryophytes is haploid and gametophyte. It produces male and female gametes.

The male sex organ is antheridium and the female sex organ is archegonium. Water carries antherozoids to the archegonium for fertilisation.

Sporophyte in bryophytes

The zygote develops into a multicellular sporophyte. The sporophyte remains attached to the photosynthetic gametophyte and gets nourishment from it.

Some sporophyte cells undergo meiosis and produce haploid spores. These spores germinate to form gametophytes.

Importance of bryophytes

Bryophytes help in plant succession on bare rocks and soil. Mosses with lichens are among the first organisms to colonise rocks.

Sphagnum provides peat, which is used as fuel and packing material. Mosses also reduce soil erosion by forming dense mats on soil.

Liverworts and Mosses

Bryophytes are divided into liverworts and mosses. Both groups need water for fertilisation, but their body form and reproduction show clear differences.

This comparison often appears in class 11 biology chapter 3 notes because NCERT gives Marchantia, Funaria and Sphagnum as key examples.

Liverworts

Liverworts usually grow in moist, shady habitats such as stream banks, damp soil and bark of trees. Marchantia is a common example.

The plant body of a liverwort is thalloid and dorsiventral. Asexual reproduction occurs by fragmentation or by gemmae formed in gemma cups.

Mosses

The moss gametophyte has two stages: protonema and leafy stage. Protonema develops directly from a spore.

The leafy stage develops from secondary protonema as a lateral bud. Common examples are Funaria, Polytrichum and Sphagnum.

Pteridophytes: First Vascular Land Plants

Pteridophytes are the first terrestrial plants to possess vascular tissues, xylem and phloem. They include horsetails and ferns.

The main plant body is a sporophyte differentiated into true root, stem and leaves. This makes pteridophytes more advanced than bryophytes in body organisation.

Sporophyte and sporangia

The pteridophyte sporophyte bears sporangia on leaf-like structures called sporophylls. In some plants, sporophylls form strobili or cones.

Sporangia produce spores by meiosis in spore mother cells. These spores germinate into small, multicellular, free-living gametophytes called prothallus.

Need for water in fertilisation

Pteridophyte gametophytes require cool, damp and shady places. Water is required for the transfer of antherozoids to archegonium.

Fusion of male gamete with egg forms the zygote. The zygote develops into the dominant sporophyte.

Homospory and heterospory

Homosporous pteridophytes produce one kind of spore. Most pteridophytes are homosporous.

Heterosporous pteridophytes produce two kinds of spores: microspores and megaspores. Selaginella and Salvinia are examples.

Heterospory and Seed Habit

Heterospory class 11 biology is important because it is linked with the evolution of seed habit. Heterospory means production of microspores and megaspores by the same plant group.

Microspores give rise to male gametophytes, while megaspores give rise to female gametophytes. In Selaginella and Salvinia, the female gametophyte remains on the parent sporophyte for some time.

Significance of heterospory

Heterospory is considered a precursor to the seed habit. This is because the female gametophyte is retained on the parent sporophyte.

The zygote develops into a young embryo inside the female gametophyte. This shows an evolutionary step towards seed formation.

Classes of pteridophytes

Pteridophytes are classified into four classes.

1. Psilopsida: Psilotum
2. Lycopsida: Selaginella, Lycopodium
3. Sphenopsida: Equisetum
4. Pteropsida: Dryopteris, Pteris, Adiantum

Gymnosperms: Plants with Naked Seeds

Gymnosperms are plants in which ovules are not enclosed by an ovary wall. Their seeds remain exposed before and after fertilisation.

The word gymnosperm comes from gymnos meaning naked and sperma meaning seed. Common examples include Cycas, Pinus, Cedrus and Ginkgo.

Plant body of gymnosperms

Gymnosperms include shrubs, medium-sized trees and tall trees. Sequoia is one of the tallest tree species.

Roots are usually tap roots. Pinus has mycorrhizal roots, while Cycas has coralloid roots associated with nitrogen-fixing cyanobacteria.

Leaves and adaptation

Gymnosperm leaves are adapted to withstand extremes of temperature, humidity and wind. In conifers, needle-like leaves reduce surface area.

Thick cuticle and sunken stomata reduce water loss. These features help gymnosperms survive in dry or cold conditions.

Reproduction in gymnosperms

Gymnosperms are heterosporous. They produce microspores and megaspores in microsporangia and megasporangia.

Male cones bear microsporophylls and microsporangia. Female cones bear megasporophylls with ovules.

Pollen grains are carried by air currents to the ovules. After fertilisation, the zygote forms an embryo and ovules develop into naked seeds.

Angiosperms: Flowering Plants with Enclosed Seeds

Angiosperms are flowering plants in which pollen grains and ovules develop in flowers. Their seeds are enclosed inside fruits.

They form an exceptionally large plant group found in many habitats. Their size ranges from the smallest Wolffia to tall Eucalyptus trees over 100 metres.

Importance of angiosperms

Angiosperms provide food, fodder, fuel, medicines and many commercial products. They are the most familiar group of plants in daily life.

The NCERT Class 11 Biology chapter Plant Kingdom divides angiosperms into dicotyledons and monocotyledons. This classification is introduced after gymnosperms.

Dicotyledons and monocotyledons

Dicotyledons have two cotyledons in the seed. Monocotyledons have one cotyledon in the seed.

This distinction helps classify flowering plants. It also connects Plant Kingdom with later chapters on plant morphology and anatomy.

Gymnosperms and Angiosperms Difference

Gymnosperms and angiosperms both produce seeds, but their seed covering is different. This is the main point behind gymnosperms and angiosperms difference in NCERT exercises.

Gymnosperms have exposed ovules and naked seeds. Angiosperms have ovules inside flowers and seeds enclosed within fruits.

Important Terms in Plant Kingdom

The Plant Kingdom chapter uses terms from classification, life cycles and reproduction. These terms are useful for short answers and NCERT exercise questions.

Thallus

Thallus is an undifferentiated plant body that is not divided into true root, stem and leaves.

Pyrenoid

Pyrenoid is a storage body found in chloroplasts of many green algae. It contains protein besides starch.

Rhizoid

Rhizoids are root-like structures that attach bryophytes to the substratum.

Gametophyte

Gametophyte is the haploid phase that produces gametes. It is dominant in bryophytes.

Sporophyte

Sporophyte is the diploid phase that produces spores by meiosis. It is dominant in pteridophytes, gymnosperms and angiosperms.

Protonema

Protonema is the first stage of the moss gametophyte. It develops directly from a spore.

Prothallus

Prothallus is the small, multicellular gametophyte of pteridophytes.

Sporophyll

Sporophyll is a leaf-like structure that bears sporangia.

NCERT-Style Questions from Plant Kingdom

Exercise questions from Plant Kingdom often ask for classification basis, life cycle stages, ploidy and differences between plant groups. Strong answers use the correct plant group, reproductive structure and example.

Q1. What is the basis of classification of algae?

Algae are classified mainly on pigments, stored food, cell wall and flagellar characters.

Explanation:

Chlorophyceae have chlorophyll a and b and store starch. Phaeophyceae contain fucoxanthin and store laminarin or mannitol.

Fact:

Rhodophyceae contain r-phycoerythrin and store floridean starch.

Q2. Why are bryophytes called amphibians of the plant kingdom?

Bryophytes are called amphibians of the plant kingdom because they live on soil but need water for sexual reproduction.

Explanation:

Their antherozoids need water to reach the archegonium. Fertilisation occurs only when water is available.

Example:

Marchantia, Funaria and Sphagnum are bryophytes.

Q3. What is heterospory?

Heterospory is the production of two kinds of spores: microspores and megaspores.

Explanation:

Microspores form male gametophytes, while megaspores form female gametophytes. This condition is seen in Selaginella and Salvinia.

Fact:

Heterospory is considered a precursor to seed habit.

Q4. Why are gymnosperms called naked-seeded plants?

Gymnosperms are called naked-seeded plants because their ovules are not enclosed by an ovary wall.

Explanation:

Their seeds remain exposed before and after fertilisation. The ovules are borne on megasporophylls, which may form female cones.

Example:

Pinus, Cycas and Ginkgo are gymnosperms.

Q5. How are liverworts different from mosses?

Liverworts usually have a thalloid, dorsiventral body, while mosses have protonema and leafy stages.

Explanation:

Marchantia reproduces asexually through gemmae in gemma cups. Funaria has a leafy gametophyte and a more elaborate sporophyte.

Fact:

Both liverworts and mosses belong to bryophytes.

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