These notes for CBSE Class 11 Biology, Chapter 3, focus on the Plant Kingdom. They introduce key terms like phylogeny, zoospores, gametophyte, sporophyte, archegonium, antheridium, megasporangium, and sporophyll. The notes also touch upon numerical, cytotaxonomy, and chemotaxonomy. A significant portion details algae as simple, thalloid, chlorophyllous plants, often aquatic. The classification then delves into Bryophytes, specifically Liverworts (e.g., Riccia, Marchantia) with their dorsiventrally flattened thallus and reproduction via fragmentation and gemmae, and Mosses (e.g., Funaria, Polytrichum) characterized by a protonema stage and leafy shoots. Life cycle patterns like Diplontic, Haplo-diplontic, and Diplontic are explained with examples. These notes are ideal for revising the Plant Kingdom chapter for exams.
Last optimized 10 Aug 2026
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| 1- | Phylogeny | - | Evolutionary history of organism . | |
| 2- | Zoospores | - | Motile spores with flagella . | |
| 3- | Gametophyte | - | Haploid stage of plant, producing gametes. | |
| 4- | Sporophyte | - | Diploid stage of plants producing spores. | |
| 5- | Archegonium | - | Female reproductive structure. | |
| 6- | Antheridium | - | Male reproductive structure. | |
| 7- | Megasporangium | - | The structure which bears megaspores. | |
| 8- | Sporophyll | - | Leaf bearing sporangia producing spores. |
| - | Numerical taxonomy | - | based on several features compared collectively by computer. | ||
| - | Cytotaxonomy | - | based on cytological features. | ||
| - | Chemotaxonomy | - | based on chemical constituent. | ||
| Algae – | |||||
| - | Group of chlorophyllous, simple, thalloid plants. | ||||
| - | Largely aquatic, grow on soil, stone, wood etc or symbiotic. | ||||
| - | Unicellular to large filamentous. | ||||
Economically useful as-
a) Large photo synthesiser, release 02 .
b)Food for aquatic animals, humans.
c)Produce Algin (Brown algae), carrageen (red algae), agar (gelidium, gracilaria)
| Chlorophyceae | Phaeophyceae | Rhodophyceae |
- Green algae chlorophyll a&b dominant. Unicellular to filamentous. - Chloroplast of different shape( cup, spiral, ribbon) with pyrenoids . - Stored food starch. - Reproduction – vegetative-fragmentation Asexual - by zoospores - Sexual - by gametes(iso, aniso and oogamus). - egVolvox, Ulothrix, Spirogyra, Chara etc. |
-Brown algae. - Xanthophyl, Fucoxanthin dominant others are chl. a, c cartenoid. - Simple branched filamentous to profusely branched large body. - Gelatinous coating on cell wall. - Stored food Mannitoland Laminarin.Reproduction - Vegetative by fragmentation Asexual By biflagellate (lateral) zoospores. Sexual by gametes(Iso, Aniso and Oogamy). - eg. Laminaria,Sargassum. |
- phycoerythrin (dominant) and others chlorophyll a and d. - Marine on surface or in great depths, multi cellular. - Stored food – Floridean starch. -Red algae - Reproduction Vegetative by fragmentation Asexual by non motile spores Sexual by oogamy. - eg. Gracilaria, Gelidium |
Group of autotrophic plants with thallus having true roots, stem and leaves with multi cellular sex organs.
Occurs on damp, humid and shaded soil.
Root like rhizoids present.
-Main plant body gametophyte bears Antheridia and Archegonia. Biflagellate antherozoids produced from Antheridium and reach through water to egg in Archegonium.
-Zygote forms sporophyte which produces haploid spores to give rise to new plants.
Types of Bryophytes
Mosses
1.Thallus dorsiventrally flattened (Liver shaped), leafy members with leaf like appendages. 2. Asexual reproduction by fragmentation , gemmae formation.
3.Sexual reproduction - antheridia and archegonia produced. 4. Antherozoids fuse with egg to form zygote which give rise to Sporophyte. 5. Sporophyte - with foot, seta & capsule. 6. Spores give rise to new plant (gametophyte).
eg. Riccia, Marchantia etc.
Marchantia
- Thallus : Two stages (gametophyte) –
(a) Thread like Protonema (b)erect Leafy stage. 1. Reproduction :
Vegetative by Fragmentation of protonema
& Sexual by antherozoids &egg. 2. Zygote forms Sporophyte with foot, seta
&capsule.
-Sporophyte forms spores which germinate to form protonema.
eg. Funaria, Polytrichum etc.
Funaria
| Pteridophyte: | |||
| - | Group of first terrestrial plants having vascular tissue viz. Xylem & Phloem. | ||
| - | True stem, root & leaf. | ||
| - | Found on damp, shady places. Sporophyte makes main plant body. | ||
| - | Sporophylls of Sporophyte bear sporangia (sori) onventral side producing haploid spores. | ||
| - | spores give rise to Prothallus which is leafy & autotrophic. | ||
| - | Prothallus bears sex organs – male – Antheridium and female- Archegonium. | ||
| - | Fertilisation leads into zygote formation which produces diploid Sporophyte. | ||
| Heterospory and Seed habit: | |||
| - | Two types of spores Microspore and Megaspore are produced in some members viz. Selaginella, Salvinia. | ||
| - | called Heterospory. | ||
| - | Heterospory is considered as begining of seed habit in terrestrial plants. | ||
| eg. Pteris, Dryopteris etc. | |||
| GYMNOSPERMS | |||
| - | Medium sized trees and shrubs. | ||
| - | Main plant body Sporophyte | ||
| - | In some members roots may have fungal association called Mycorrhiza. | ||
| -bilus. | |||
| - | Microspore i.e. pollens reaches to ovules.Pollen tubes help to transfer male gametes up to egg of archegonia present in female gametophyte of ovule.
|
||
| Zygote develops in an embryo inside seed | |||
| - | e.g. Cycas, Pinus ,Cedrusetc. | ||
| ANGIOSPERMS | |||
| Large no. of plants in varied habitats, small microscopic plants (Wolfia) to large trees | |||
| - | Group of plants having covered seeds in fruits. | ||
| - | Produce flowers having reproductive organs. | ||
| - | Most evolved plants. |
-Androecium is male part and one unit is stamen.
-Gynoecium is female part and one unit is carpel and has ovules.
-Ovule bears embryo sac.
-Embryo sac is seven celled and has Egg
01 – haploid. Synergids
02 – haploid.
Antipodals
03 - haploid. Secondary nucleus
04 – diploid.
-Reproduction by vegetative and sexual methods.
-In sexual reproduction pollens shed off and reach to stigma of Gynoecium by pollination.
-Pollen germinates to form pollen tube with two male gametes and one tube nucleus.
-One gamete fuses with egg (Syngamy) and other with secondary nucleus to form PEN (primary endosperm nucleus). The whole process is called Double fertilization.
-Zygote forms embryo and PEN forms Endosperm in ovule which changes into seed inside fruit.
-Ovary wall changes into Pericarp (fruit wall).
-Alternation of generation occours.
Plant life cycle and alternation of Generation –
-Alternate stages of haploid (n) and Diploid (2n) phase in life cycle of plants.
Haplontic |
Diplontic |
Haplodiplontic |
- Dominating phase haploid (n). -only zygote diploid (2n). -Haploid spores form the main plant body eg. Algae viz. Ulothrix,Spirogyra etc. |
-Dominating phase diploid (2n). -Haploid phase only in single cell or few celled gametophyte. -Zygote forms embryo which forms Sporophyte (main plant body). eg. Gymnosperms& Angiosperms |
-Intermediate i.e.haploid & diploid stages equal. -Gametophyte & Sporophyte stages both may be free living. eg. Bryophytes & Pteridophyte. |
Phylogeny refers to the evolutionary history of an organism, which is important for understanding plant classification.
Zoospores are motile spores that possess flagella, enabling them to move, typically found in algae.
The gametophyte is the haploid stage of a plant that produces gametes, while the sporophyte is the diploid stage that produces spores.
Algae are chlorophyllous, simple, thalloid plants that are largely aquatic and can range from unicellular to large filamentous forms.
Examples of Liverworts provided are Riccia and Marchantia.
Liverworts have a dorsiventrally flattened, liver-shaped thallus, and leafy members have leaf-like appendages.
In Mosses, the gametophyte has two stages: a thread-like protonema and an erect leafy stage.
A Diplontic life cycle is dominated by the diploid sporophyte phase (2n), with only the zygote being diploid, and the main plant body is haploid (n).
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