CBSE Class 11 Biology Revision Notes Chapter 3

CBSE Class 11 Biology Revision Notes Chapter 3 – Plant Kingdom

Chapter 3 of Class 11 Biology introduces students to the Plant Kingdom and the different ways in which it is classified into different categories. Since this chapter can be a little challenging given all the technical terms that students will need to know and memorise, Extramarks offers concise Revision Notes for this chapter that summarise all the important topics covered in the chapter. Students can access these at any time from the Extramarks’ website.

Access Class 11 Biology Chapter 3 – Plant Kingdom

In the previous chapter, students learned that Whittaker divided living organisms into five kingdoms based on cell framework difficulty (prokaryotic and eukaryotic), body specificity (unicellular and multicellular), and method of nutrients (autotrophs and heterotrophs). These five kingdoms were Monera, Protista, Fungi, Plantae and Animalia.

In this chapter, they will learn about how the Plant Kingdom is further divided into 5 categories namely algae, bryophytes, pteridophytes, gymnosperms, and angiosperms. 

Classification of the Plant Kingdom:

All categorisation systems, from Aristotle to the twentieth century, can be grouped into three categories:

• Artificial Intelligence

The classification in this system is based on a few morphological characteristics. Theophrastus, Pliny, and Linnaeus employed a made-up categorisation system.

• System of Nature

The categorisation under this method is based on all of the linked traits. Externally and inside. Bentham and Hooker, Adanson, and Candolle utilised a natural categorisation system.

• System of Phylogeny

Plant classification is based on evolutionary relationships. Eichler, Blessy, Whittaker, Engler, Prantl, and Hutchinson were the first to apply phylogeny for categorisation.

3.1 ALGAE:

• Phycology is the branch of biology that studies algae.

Phycos=seaweed

Logos=study

• Fritch was the founder of phycology.
• The father of Indian phycology is M.O.P.Iyengar.
• Thallophytes are pigmented algal members.

Habitat:

Hydrophytes are plants that live in water. In an aquatic environment:

• Freshwater (Spirogyra) and marine (Sargassum). 
• Floating- Chlamydomonas, Spirogyra.
• Benthophytes are plants that stay attached to the soil at the bottom of their habitat. Chara, for example (stoneworts).
• Xerophytes: They live in the desert.
• Mesophytes thrive in medium-sized environments.
• Epizoic growth on animal bodies (Trichophillus).
• Lithophytes are plants that grow on rocks.
• Halophytes are plants that flourish in saline environments.
• Terrestrials with moist soil (Fritschiella).

Plant Body:

• A haploid gametophyte is the vegetative plant body of algae.
• They can be single-celled, flagellated (Chlamydomonas), or not (Chlorella)

Multicellular:

1. Coenobium is a colony with a predetermined number of cells and a predetermined division of labour. One of the examples is Volvox.
2. Aggregation-indefinite colony. E.g., Tetraspora 
3. Filamentous-unbranched.E.g.: Ulothrix 
4. Filamentous branches. E.g., Cladophora 
5. Siphonous- multinucleate. E.g., Vaucheria 
6. Parenchymatous, e.g, Ulva
7. Branched like higher plants. E.g., Sargassum, Chara

Nutrition:

• Autotrophs – Photosynthetic (most of them).
• Parasitic forms (rare). E.g., Cephaleuros.

Pigments:

• Chlorophyll- a, b, c, d.
• Brown algae are dominated by carotenoids (carotene) and xanthophyll (fucoxanthin).
• Phycobillins- phycocyanin and phycoerythrin.

Reproduction:

Reproduction through vegetative parts is known as vegetative reproduction.

There are various types:

• Fission 
• Fragmentation 
• Budding 
• Tubers 
• Gemmae

Asexual Reproduction-Without the Fusion of Gametes.

Mainly by:

• Zoospores within sporangia 
• Aplanospores 
• Akinete 
• Hypnospores 
• Endospore 
• Exospore  
• Monospore 
• Auxospore.

Stage Palmella

In this stage, the spores become colonial and resemble the algae Palmella. For eg. Ulothrix, Chlamydomonas, etc.

Sexual Reproduction: 

Homogametes-similar gametes.

Heterogametes-dissimilar gametes.

• Isogamy: fusion of morphologically and physiologically similar gametes. Isogamy- flagellated (Chlamydomonas ) and non-flagellated (Spirogyra).
• Anisogamy: fusion of morphologically or physiologically dissimilar gametes.

In Chlamydomonas, morphologically distinct gametes fuse. Spirogyra allows physiologically different gametes to fuse.

• Oogamy: Itis the union of morphologically and physiologically different male and female gametes. Fucus and Volvox are two examples.

Exceptional Cases:  

Unicellular antheridium and oogonium.E.g., Oedogonium.

Special Reproductive Structures: 

Conceptacles –Eg: Sargassum 

Globule (antheridium) and nucule (oogonium) Eg: Chara

Spirogyra has a unique method of sexual reproduction termed conjugation.

The life cycle has two phases: haploid and diploid, with some of them displaying generational alternation. The haploid phase and the diploid phase are alternate.

Classification of Algae:

They are divided into three groups:

1. Chlorophyceae 
2. Phaeophyceae  
3. Rhodophyceae.

3.1.1 Chlorophyceae 

The plant body of the Chlorophyceae is either unicellular, as in Chlamydomonas, colonial, as in Volvox, or filamentous, as in Spirogyra.

• Different Shapes for the Chloroplast:

1. Ribbon shaped and spiral in Spirogyra
2. Girdle shaped in Ulothrix 
3. Cup shaped chloroplast in Chlamydomonas 
4. Star-shaped in Zygnema 
5. Disc-shaped in Caulerpa 
6. Reticulate in Oedogonium.

• Chlorophyll a and b are photosynthetic pigments.
• Some foods are kept as starch, whereas others are stored as oil droplets.
• The storage bodies, known as pyrenoids, are present.
• Cellulose makes up the inner layer of the cell wall, whereas pectose makes up the outside layer.
• The participants reproduce:

1. vegetatively by fragmentation 
2. Asexually by flagellated zoospores  
3. Sexually by isogamy, anisogamy, and oogamy.

• Common Chlorophyceae members are:  

Chlamydomonas, Chlorella, Volvox, Ulothrix, Ulva, Caulerpa, Chara, Acetabularia etc.

3.1.2   Brown Algae or Phaeophyceae:

• They’re from the sea.
• Ectocarpus has simple branching filaments, whereas Sargassum, Laminaria, Fucus, and other plants have flat ribbon-shaped leaves.
• Marine plants are massive brown algae Kelps; some are free-floating, like Sargassum, while others, like Ectocarpus, are epiphytes on other plants.
• There are three parts to the plant’s body:

1. Holdfasts are anchoring structures.
2. A stipe is a stalk-like structure.
3. The frond is a leaf-like structure.

• Brown algal pigments include chlorophyll a, c, carotenoids, and xanthophylls.
• Food is stored as laminarin and mannitol, which are complex carbohydrates.
• A gelatinous coating called algin coats the exterior part of the cell wall. The hydrocolloid (hydrocolloid) algin keeps the thallus moist during low tide.
• The vacuole, which helps the thallus float, is found in the cell organelles.
• The process of fragmentation occurs during vegetative reproduction.
• Biflagellated zoospores, pear-shaped and have two flagella connected laterally, are used for asexual reproduction.
• The fusing of gametes happens during sexual reproduction. It contains:

1. Isogamy
2. Anisogamy  
3. Oogamy

• Pear-shaped gametes with two flagella connected laterally.
• Ectocarpus, Laminaria, Dictyota, Sargassum, and Fucus are the most prevalent brown algae.

3.1.3 Rhodophyceae (Red Algae):

• Also known as red algae
• They are primarily marine, with freshwater species being rare. Ex.: Betrachospermum.
• They may be found in well-lit areas as well as deep into seas.
• The thallus has many cells.
• Chlorophyll a, d, and phycoerythrin are pigments found in red algae.
• The presence of the red pigment r-phycoerythrin gives algae their red hue.
• Food is stored as Floridian starch, similar to amylopectin and glycogen.
• Fragmentation of vegetative reproduction
• Nonmotile spores reproduce asexually.
• Oogamy is a method of sexual reproduction that results in complicated post-fertilisation changes.
• Polysiphonia, Porphyra, Gracilaria, Gelidium, Betrachospermum, and other red algae are regularly seen.

Algae’s Economic Importance:

• Algae are the principal producers of the food chain. Algae provide the foundation for all aquatic species’ feeding cycles.
• Algae repair 50% of the total carbon dioxide on the planet through photosynthesis.
• It is particularly significant in the cleaning of air and water.
• Some algae can be eaten. Examples are Chlorella, Laminaria, Porphyra, Sargassum, Ulva, and Spirulina.
• Fodder is made from algae—for example, Laminaria, Sargassum, and Fucus.
• It also serves as a dietary supplement for astronauts in space. Chlorella, Spirulina, etc.
• Algin and carrageenan, water-holding compounds or hydrocolloids, are derived from red algae.
• Gelidium and Gracilaria both produce agar. Microorganisms are grown in it.
• In tissue culture experiments, it’s used to make culture media.
• It is used in the making of antibiotics. Thus, it has therapeutic significance.
• Polysiphonia and Laminaria are also employed as mineral sources.
• Chlorella and Acetabularia are crucial in biological studies.

Algae Common Names:

• Water silk-Spirogyra 
• Sea lettuce- Ulva 
• Umbrella plant-Acetabularia ( Largest unicellular algae)

3.2 Bryophytes:

• Plants have undifferentiated plant bodies that are non-vascular.
• Bryology (Bryophyte Study)
• Bryology’s Father, Hedwig
• Father of Indian bryology, S.R.Kashyap
• Because of their distinct traits, bryophytes are often known as plant amphibians.
• Bryophytes thrive in thick patches on wet, shaded surfaces such as walls, damp soil, and tree trunks.

Features

• Habitat: It has Primarily terrestrial, with some aquatic species. Riccia fluitans, for example.
• The radula is an epiphyllous plant.
• The thallus and Prostate are plant bodies. Riccia, Anthoceros, Marchantia, or Erect, for instance. Moss, for example.
• Rhizoids, which are root-like structures, aid in their soil fixation.
• The stem-like and leaf-like elements of the plant’s body are distinguished.
• There are no vascular tissues.
• Fragmentation, budding, tubers, and other vegetative reproduction are used.
• Gemmae- asexual buds in liverworts are used for asexual reproduction.
• Sexual reproduction takes place. The gametophyte is the vegetative plant body, and all members are homosporous.
• There are clusters of multicellular sex organs present.
• The male reproductive organ is the club-shaped antheridium, which generates motile biflagellate antherozoids.
• The female reproductive organ, the archegonium, is flask-shaped and produces an egg.
• The antherozoid combines with the egg to create the zygote.
• The sporophyte is not self-sustaining and relies on the photosynthetic gametophyte for nutrition.
• After meiosis, the sporophyte produces haploid spores, germinating to produce the gametophyte.
• When the haploid phase changes to the diploid phase, this is known as generational alternation.
• Both stages are multicellular.
• The gametophyte is the most common free-living photosynthetic stage.
• The sporophyte has a brief life span and is reliant on the gametophyte.
• Water is necessary for fertilisation.

Classification of Bryophytes: It has three classes:

• Hapticospida (liverworts) 
• Anthocerotopsida (Hornworts) 
• Bryopsida. (Moss)

3.2.1 Hepaticopsida or Liverworts:

• The photosynthetic plant body is flat and has a dorsiventral thallus. Riccia, Marchantia, etc.
• Rhizoids are present, which aid in the thallus’s attachment to the soil.
• The technique of fragmentation is used in vegetative reproduction. Riccia, Marchantia, etc.
• In some bryophytes, for example Marchantia, reproduction occurs in gemmae formation.
• Gemmae grow into little receptacles known as gemma cups, multicellular, asexual buds. The gemma separates from the parent body and germinates to generate the new thallus.
• Antheridia and archegonia are the sex organs found in this species. They might develop on the same thalli.
• The sporophyte is divided into three parts: the foot, the seta, and the capsule. In the shell, meiosis occurs, resulting in haploid spores that germinate into free-living thalloid gametophytes.
• Anthoceropsida or Hornworts include Anthoceros and Notothylas, for example.
• Anthoceros is the scientific name for hornworts.
• Pyrenoids are present.
• There is symbiotic nitrogen fixation.

3.2.2 Bryopsida (Moss):

• They are more advanced bryophytes.
• Protonema and the leafy stage are the two phases of the gametophyte.
• Protonema is green filamentous, branching, creeping entities that sprout immediately from the spore and possess branched rhizoids and lateral buds.
• The leafy stage emerges from the secondary protonema as a lateral bud.
• Root-like, stem-like, and leaf-like components make up the plant’s body. Consider Funaria.
• Rhizoids are branching and multicellular.
• The sex organs are found in the leafy phases.
• In secondary protonema, vegetative reproduction occurs by fragmentation and budding.
• The spore dispersion process in mosses is complex.

3.3 Pteridophytes:

• They are the earliest terrestrial plants to produce vascular tissue like the xylem and phloem. As a result, they’re also known as vascular cryptogams.
• Botanical snake, as the name suggests.
• True root, stem, wind-needle-like, and leaf are the distinct types of the plant body.
• The sporophytic generation is the plant body.
• When aerial sections are eliminated, the rhizomatous stem regenerates.
• Microphyll (as in Selaginella) or macrophyte (as in ferns) leaves can be small or enormous.
• Pteridophytes show circinate vernation (coiling of young leaves).
• There are two sorts of leaves: vegetative and fertile.
• Sporophylls are spore-bearing leaves that are fertile.
• Inside the sporangia, spores develop. After meiosis, the spore mother cells in Sporangia produce spores.
• Spores germinate to create a haploid gametophyte, a photosynthetic heart-shaped multicellular structure that contains antheridia and archegonia.
• Prothallus requires chilly, wet, and shaded conditions to develop, while water is needed for fertilisation.
• Antherozoids and egg cells are produced by antheridia and archegonia, fertilising to produce a zygote and germinating to produce a sporophyte.
• Because most pteridophytes produce similar spores, they are referred to as homosporous. Genera such as Selaginella and Salvinia generate two heterosporous spores. It is mega or giant spores and tiny or microspores. When microspores and microspores germinate, male and female gametophytes are generated.
• The female gametophyte is not free-living in heterosporous circumstances. It is maintained in the parent sporophyte until the embryo develops.
• Heterosporous pteridophytes developed into seed-bearing plants.

3.4 Gymnosperms:

• Because the ovules are not contained within or by any ovary wall, they stay exposed and produce naked seeds (no fruit covering). 
• The ovarian wall also does not contain the ovules.
• These plants were majorly prevalent during the Jurassic era
• Gymnosperm contains medium-sized and higher trees, as well as shrubs.
• The taproot system is commonly seen. They are also linked to mycorrhiza, which is the relationship between fungus and higher plant roots. Consider Pinus. As in Cycas, coralloid stems contain nitrogen-fixing bacteria.
• The stem can be branched or unbranched (Pinus) (Cycas).
• Leaves with thick cuticles and depressed stomata are suited to severe temperatures, humidity, and wind. Consider Pinus.
• Complex or straightforward leaves exist.
• As with Cycas, their stem is unbranched.
• Pinus and Cedrus have branches.
• Xylem is without vessels and have a well-developed vascular system.

3.6 Alternation of Generation:

There is a haploid gamete that alternates between gametophytic and spore-producing sporophytic production.

• The cycle of Haplontic Life

The photosynthetic phase in this type of lifecycle is a free-living gametophyte formed by haploid spores. Mitosis is the gametophyte that creates gametes that further unite to form the zygote, which symbolises the sporophytic generation. Meiosis occurs in the zygote, resulting in haploid spores. The Gametophytic phase is dominating in this area. Chlamydomonas, for example.

• The cycle of Diplontic Life

The phase of the plant is the diploid sporophyte, which is photosynthetically autonomous. One to a few celled haploid gametophytes nourishes during the gametophytic period. Angiosperms and Gymnosperms, for example, are dominated by the sporophytic stage.

• Cycle of Haplo-Diplontic Life

In this kind, both the haploid and diploid phases are multicellular and generally free-living. Pteridophytes and bryophytes are two examples.

Fast Track Revision:

• The Kingdom of Plants Cryptogamae (non-flowering seedless plants) and Phanerogamae (flowering seedless plants) (flowering, seed-bearing plants).
• Cryptogame is split into three groups based on the plant body: Thallophyta, Bryophyta, and Pteridophyta.
• Thallophytes have split once again.

1. Algae (pigmented thallophytes)  
2. Fungi (non-pigmented thallophytes)  
3. Lichens: Bears symbiotic association between algae and fungi.

• Phanerogamae is divided into two. 

1. Gymnosperms (naked seed plants) and,
2. Angiospermae (covered seeded plants).

• Angiosperms are separated into two groups once again.

1. Monocots contain just one cotyledon, a fibrous root system, and leaves with parallel venation.
2. Dicotyledons have two cotyledons, a taproot system, and leaves with reticulate venation.

• Algae are aquatic creatures that are relatively basic, thalloid, and autotrophic.
• Algae are divided into three groups based on the pigments they produce and the food they store: Chlorophyceae, Phaeophyceae, and Rhodophyceae.
• Asexual reproduction is performed by various spores, while sexual reproduction is accomplished by synthesising gametes that display isogamy, anisogamy, and oogamy.
• Bryophytes are plants that may survive on soil but require water for sexual reproduction. In comparison to algae, their plant body is more distinct.
• Rhizoids have a thallus-like plant body with fixing mechanisms that can be upright. They have structures that resemble roots, leaves, and stems.
• Liverworts, hornworts, and mosses are the three types of bryophytes.
• The plant body and dorsiventral of liverworts are thalloid.
• Mosses have a narrow axis and spirally arranged leaves.
• The plant body is a gametophyte, and the zygote creates a multicellular organism termed the sporophyte once the gametes fuse.
• The plant body of pteridophytes is a sporophyte, which has a root, stem, and leaves.
• In Pteridophyte, the sporophyte has sporangia, which generates spores that germinate into gametophytes.
• The gametophyte of Pteridophyte has both male and female sex organs, known as antheridia and archegonia.
• Water is required for fertilisation.
• Gymnosperms are plants that produce naked seeds that stay exposed after fertilisation.
• Gymnosperms produce microsporophyll and megasporophyll. The sporophylls give birth to Microsporangia and Megasporangia.
• Microsporophyll and megasporophyll are two types of sporophylls.
• The male gamete is released into the ovule by the pollen tube created by the pollen grain. Archegonia fuse with the egg cell in the ovule. The zygote grows into an embryo after fertilisation, while the ovules eventually become seeds.
• The male sex organs, the stamen, and the female sex organ, the pistil, are both present in angiosperm flowers.
• Anther and filament make up the stamen.
• Ovary, style, and stigma all reside in the pistil.

Biology Chapter 3 Class 11 Notes – Free Download

• Extramarks offers clear and concise notes to Class 11 Biology Chapter 3 that will help students cover this chapter more effectively. These notes summarise all the important topics covered in this chapter from a single platform so that students can quickly go through them right before their exams. 

Biology Notes for Class 11 Chapter 3 Cover Some of the Topics

These topics are as follows:-

Classification of Plants

Plant classification, or taxonomy, focuses on the differentiation of the plant body, tissues engaged in transportation, and the existence of seeds, among other things. The divisions are as follows:

• Thallophyte

Fungi, algae, and bacteria are examples of microorganisms. The cell wall of algae is made up of cellulose, and food is stored in the form of starch.

• Bryophyta

These plants may grow on land as well as in water. Some of the examples are Moss, liver warts, and other examples

• Pteridophyte

These plants are devoid of flowers and seeds. Ferns are an example of a Pteridophyte.

• Gymnosperm

There is no ovary, and the seeds are uncoated.

• Angiosperm

Within an ovary, the seeds are covered and formed.

• Monocot

Only one cotyledon is found in this form of angiosperm. Leaf veins run parallel, and vascular bundles are dispersed. The root system is haphazard. Rice, wheat and maize are examples of monocots.

• Dicot

In dicot angiosperms, there are two seed leaves. Veins branch and vascular bundles are arranged in a ring. Taproots are also found. Potatoes, peas, and bananas are among the examples.

Eichler’s Classification

Eichler’s categorisation established a method that categorises plants into two groups. The chapter explores two divisions – cryptogamic and phanerogamic.

Cryptogame plants are seedless and flowerless. Phanerogamae, on the other hand, is a seed-bearing plant. These are higher plants where the body is separated into the stem, roots, and leaves.

Classification of Algae

There are three types of algae:

• Chlorophyceae

These are majorly green algae. The green colour is the result of the presence of Chlorophyll A and B. Spirogyra is an example of Chlorophyceae.

• Rhodophyceae

Red pigment is found in these algae. R-phycoerythrin is a red pigment- e.g., Gelidium.

• Phaeophyceae

Brown algae make up the majority of these marine algae. Carotenoids and xanthophyll are the pigments in question. Sargassum, for instance.

Chapter 3 may be rewarding if adequately prepared. The Biology Chapter 3 Notes for Class 11 provide all relevant information.