Notes Chapter 12 Plant Kingdom
Class 11 students can refer to Chapter 12 Plant Kingdom notes given below which is an important chapter in the class 11 Biology book. These notes and important questions and answers have been prepared based on the latest CBSE and NCERT syllabus and books issued for the current academic year. Our team of Biology teachers has prepared these notes for class 11 Biology for the benefit of students so that you can read these revision notes and understand each topic carefully.
Plant Kingdom Notes Class 11 Biology
Refer to the notes and important questions given below for Plant Kingdom which is really useful and has been recommended by Class 11 Biology teachers. Understanding the concepts in detail and then solving questions by yourself will help you to learn all topics given in your NCERT Books.
o FIRST PLANT GROUP
• where sporophyte becomes the main plant body
• where main plant body (sporophyte) is truly differentiated into true root, stem and leaves.
• Possess well-differentiated vascular tissues.
o The sporophytes bear sporangia which produce spores.
o The spores germinate to form gametophytes
• which require cool, damp places to grow.
o The gametophytes bear male and female sex organs called antheridia and archegonia, respectively.
o Water is required for transfer of male gametes to archegonium (restriction for distribution) where zygote is formed after fertilisation.
o The zygote produces a sporophyte.
o Microphylls (small leaf) is found in selaginella
o Macrophylls (large leaf) are found in fern.
o Sporophylls are sporangia bearing leaf.
o In some pteridophytes, Sporophylls are compactly arranged and form cone or strobilus.
o Cones are found in Equisetum and selaginella.
o Sporangia either produce
• only one type of spores i.e. HOMOSPOROUS
• Two types of spores i.e. HETEROSPOROUS.
o HETEROSPOROUS pteridophytes
• Megaspore which germinate to form female gametophyte
• Microspore germinate to form male gametophyte.
o Selaginella and salvinia is example of heterospory.
o The female gametophyte in HETEROSPOROUS PTERIDOPHYTE are retained on the parent sporophytes for variable periods.
• The development of the zygotes into young embryos take place within the female gametophytes.
• This event is a precursor to the seed habit considered an important step in evolution.
o Inside sporangia, spore mother cell produces haploid spores after meiosis.
o This spore germinates to form haploid inconspicuous, small but multicellular free-living, mostly photosynthetic thalloid gametophytes called prothallus.
o These gametophytes require cool, damp, shady places to grow.
(require water for fertilization).
o The pteridophytes are further classified into four classes:
• Psilopsida (Psilotum);
• Lycopsida (Selaginella, Lycopodium),
• Sphenopsida (Equisetum) and
• Pteropsida (Dryopteris, Pteris, Adiantum).
o Main plant body is sporophyte.
o Tap root system.
o Roots in some genera have fungal association in the form of mycorrhiza (Pinus)
o In some others (Cycas) small specialised roots called coralloid roots are associated with N2- fixing cyanobacteria.
o Cycas has unbranched stem.
o Pinus & cedrus have branched stem.
o The leaves in gymnosperms are well-adapted to withstand extremes of temperature, humidity and wind.
o In conifers(Pinus), the needle-like leaves reduce the surface area.
• thick cuticle and sunken stomata also help to reduce water loss.
o All gymnosperms are heterosporous
• they produce haploid microspores and megaspores.
o The two kinds of spores are produced within sporangia that are borne on Sporophylls
o These Sporophylls are compactly & spirally arranged in cone/strobilus.
o The strobili bearing microsporophylls and microsporangia are called
o The microspores develop into a male gametophytic generation which is highly reduced and is confined to only a limited number of cells.
o This reduced gametophyte is called a pollen grain.
o The development of pollen grains take place within the microsporangia.
o The cones bearing megasporophylls with ovules(megasporangia) are called FEMALE STROBILI.
o The megaspore mother cell is differentiated from one of the cells of the nucellus.
o The nucellus is protected by envelopes and the composite structure is called an ovule(megasporangium)
o The ovules are borne on megasporophylls
o Megasporophylls clustered to form the female cones.
o The megaspore mother cell divides meiotically to form four megaspores.
o One of the megaspores enclosed within the megasporangium develops into a multicellular female gametophyte that bears two or more archegonia or female sex organs.
o The multicellular female gametophyte is also retained within megasporangium.
o Gametophytes are dependent on sporophyte and don’t have independent existence.
o Pollination by wind
o Pollen grain come in contact with the opening of the ovules borne on megasporophylls.
o The pollen tube carrying the male gametes grows towards archegonia in the ovules and discharge their contents near the mouth of the archegonia.
o Water is not required for fertilization.
o Following fertilisation, zygote develops into an embryo and the ovules into seeds.
o Endosperm is haploid and before fertilization structure.
o These seeds are not covered i.e. naked seed (seeds are not enclosed in fruit because ovary is absent in gymnosperm).
o Pinus is a monoecious
• Microsporangia and megasporangia born on same plant.
o Cycas is dioceous plant
• Microsporangia and megasporangia born on different plants.
o Life cycle is DIPLONTIC.
3. ANGIOSPERM CLASSIFICATION METHODS
o ARTIFICIAL SYSTEM OF CLASSIFICATION:
• They were based mainly on
• vegetative characters
• on the reproductive structure
• Superficial morphological characteristics
• Mistake à They separated the closely related species.
• Why à The vegetative characters are more easily affected by environment.
• Linnaeus used androecium morphology for classification of plant.
o NATURAL SYSTEM OF CLASSIFICATION:
• It was based on natural affinities among the organisms as well as internal features, like ultrastructure, anatomy, embryology and phytochemistry.
• Bentham & Hooker proposed this system.
o PHYLOGENETIC SYSTEM OF CLASSIFICATION:
o It is based on evolutionary relationships between the various organisms.
o Presently acceptable system.
o This assumes that organisms belonging to the same taxa have a common ancestor.
4. In absence of fossil evidences, taxonomist take help from various branch to solve the problems in classification .
5. NUMERICAL TAXONOMY:
o It stores computerised data of all observable characters.
o Number and codes are assigned to all the characters and the data are then processed.
o In this way each character is given equal importance and at the same time hundreds of characters can be considered.
6. Cytotaxonomy that is based on cytological information like chromosome number, structure, behaviour.
7. Chemotaxonomy that uses the chemical constituents of the plant to resolve confusions.
o The pollen grains and ovules are developed in specialised structures called flowers.
o The seeds are enclosed by fruits.
o The angiosperms are an exceptionally large group of plants occurring in wide range of habitats.
o They provide us with food, fodder, fuel, medicines and several other commercially important products.
o Wolfia is smallest angiosperm plant.
o In angiosperms, the male sex organs (stamen) and female sex organs (pistil) are borne in a flower.
9. One male gamete fuses with egg cell (syngamy) and other fuses with diploid secondary nucleus (triple fusion). This phenomenon of two fusions is called double fertilisation and is unique to angiosperms.
10. Endosperm is triploid & post fertilization structure.
11. The angiosperms are divided into two classes – the dicotyledons and the monocotyledons.
12. ALTERNATION OF GENERATIONS:
o Alternate occurrence of gametes producing gametophyte and spore producing sporophyte in LIFE-CYCLE is called ALTERNATION OF GENERATIONS.
13. HAPLONTIC life cycle
o the main plant body is gametophyte(n),
o zygote is the only diploid in its life cycle
o characterised by ZYGOTIC MEIOSIS.
o EXAMPLES: volvox, spirogyra and some species of chlamydomonas.
14. DIPLONTIC LIFE-CYCLE:
o Here, main plant body is diploid sporophyte.
o Sporic meiosis.
o Haploid gametophytes are very reduced type(one to few celled).
o Examples: Gymnosperm, Angiosperm and fucus (brown algae).
15. HAPLO-DIPLONTIC LIFE CYCLE:
o In this type of life cycle, plants exhibit an intermediate condition both phases are multicellular.
o Bryophytes and pteridophyte are the examples.
o In bryophyte, gametophyte is dominant whereas in Pteridophyta, sporophyte is dominant.
o Sporic meiosis.
16. Pteridophyte is the group where gametophyte and sporophyte both are independent and free living.
17. Ectocarpus, kelp (brown algae), polysiphonia (red algae) show haplo-diplontic life cycle.
18. Algae is the group in plant kingdom which show all three type of alternation of generations.