Plant Kingdom Online Test 8th Science Lesson 7 Questions in English

Explanation

The living organisms found on the earth are different in their structures, habit, habitat, mode of nutrition and physiology. The estimated number of species on the earth is 8.7 million.

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The estimated number of species on the earth is 8.7 million. Among them 6.5 million (1 million =10 lacks) species are living on land, 2.2 million species in the ocean. In these 4,00,000 species are flowering plants.

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The living organisms show lot of similarities and differences so that they can be arranged into many groups systematically. The plant kingdom includes thallophytes, bryophytes, pteridophytes, gymnosperms and angiosperms.

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Taxonomy is the branch of biology that deals with the study of identification, classification, description and nomenclature of living organisms.

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The word taxonomy is derived from two Greek words (Taxis: arrangement and Nomos: laws.) The word ‘Taxonomy’ was first coined by Augustin-Pyramus de Candolle.

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There are four types of classification.

1. Artificial system of classification 2. Natural system of classification 3. Phylogenetic system of classification 4. Modern system of classification

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Artificial system of classification is the earliest system of classification in plants. Plants are classified on the basis of one or few morphological characters

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The most famous artificial system of classification is Linnaeus classification which was proposed by Carolus Linnaeus in Species plantarum.

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In this system, plants are classified on the basis of several characters. Bentham and Hooker’s classification is an example of Natural System of Classification. This system of classification is based on morphological and reproductive characters of the seeded plants.

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Bentham and Hooker published their Natural system of Classification in their book named Genera Plantarum in 3 volumes.

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Natural system of classification is widely used in many Herbaria (herbarium is defined as the collection of pressed, dried plants pasted on a sheet and arranged according to any one of the accepted systems of classification) and botanical gardens all over the world.

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The division spermatophyta are divided into 3 classes:

 Dicotyledonae
 Gymnospermae
 Monocotyledonae

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Dicotyledonae:

 Seed has two cotyledons.
 Leaves have reticulate venation
 Tap root system is present.
 Flowers are tetramerous or pentamerous

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Gymnospermae (Naked seed plants):

 Plants of this class have no fruit.
 It has three families, they are
1. Cycadaceae
2. Coniferae
3. Gnetaceae

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Monocotyledonae:

 Seed has single cotyledon.
 Leaves have parallel venation.
 Fibrous root system is present
 Flowers are Trimerous

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The naming of an organisms with two words are known as Binomial Nomenclature. For example, the binomial name of mango is Mangifera indica.

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Binomial system had been properly made used by Linnaeus in his book, “Species Plantarum.” The naming of an organisms with two words are known as Binomial Nomenclature.

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The system of naming the plants on scientific basis is known as Botanical nomenclature. Binomial name was first introduced by Gaspard Bauhin in the year of 1623.

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Largest Herbarium of India is in Kolkata, which has more than 10,00,000 (one million) species of herbarium specimens.

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Algae are chlorophyll bearing simple, primitive plants and are autotrophs. Most of the algae are living in aquatic region. It may be fresh water or marine water. Very few algae can survive in terrestrial conditions.

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Algae belongs to Thallophyta, and the plant body of algae are called thallus. i.e. the plant body is not differentiated into root, stem and leaf.

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Some algae are very minute and float on the surface of the water. These algae are called Phytoplankton.

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The rules and recommendations regarding binomial nomenclature were found in ICBN (International Code of Botanical Nomenclature) now it is known as ICN (International Code of Nomenclature).

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Some of the algae are symbionts (algae living with fungi and they both are mutually benefitted.) e.g. Lichen. A few species of them are epiphytes (growing on another plants).

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Plant body of the algae are unicellular or multicellular. Unicellular motile (Chlamydomonas), nonmotile. (Chlorella).

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Multicellular unbranched filaments (Spirogyra) and branched filaments (Cladophora). Some algae are giant kelp – Macrocystis. Some algae are living as colonial form – Volvox. Alga like Chara resembles largest plant body and it possess well developed sex organs.

Explanation

Three types of reproduction are seen in algae:

• Vegetative reproduction by fragmentation e.g. Spirogyra.

• Asexual reproduction by spore formation e.g. Chlamydomonos.

• Sexual reproduction by means of fusion of gametes e.g. Spirogyra, Chara

Explanation

Class – Type of pigment

Bluegreen algae – Phycocyanin

Green algae – Chlorophyll

Brown algae – Fucoxanthin

Red algae – Phycoerythirin

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 Bluegreen algae (Cyanophyceae)
 Green algae (Chlorophyceae)
 Brown algae (Phaeophyceae)
 Red algae (Rhodophyceae)

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 Bluegreen algae (Cyanophyceae) – Cyanophycean Starch
 Green algae (Chlorophyceae) – Starch
 Brown algae (Phaeophyceae)- Laminarian starch and Manitol
 Red algae (Rhodophyceae)- Floridian Starch

Explanation

Algae are consumed as food by the people in Japan, England and also in India. e.g. Ulva, Spirulina, Chlorella etc. Some algae are used as a food for domestic animals. e.g. Laminaria, Ascophyllum.

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Some of the blue green algae are essential for the fixing of atmospheric nitrogen into the soil, which increases the fertility of the soil. e.g. Nostoc, Anabaena.

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Agar Agar is extracted from some red algae, namely Gelidium, Gracillaria, etc., which is used to prepare growth medium in laboratories.

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Chlorella pyrenoidosa is used in space travel to get rid of CO2 and decompose human wastes. Iodine is obtained from brown algae like Laminaria (kelp).

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Fungi (singular – fungus) belongs to thallophyta because the plant body is not differentiated into root, stem, and leaves.

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The plant body of fungus consists of filament like structures called as hyphae. Several hyphae arranged in the form of network called mycelium. There are two types of mycelium found in fungi, namely septate mycelium and aseptate mycelium.

Explanation

If the cross wall is seen between the cell, it is called septate mycelium. If the cross wall is not seen, it is called aseptate mycelium. When aseptate mycelium contains many nuclei, it is called as coenocytic mycelium .

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The cells of fungi are multicellular and eukaryotic organisation. Some species of fungi like yeast is unicellular and eukaryotic cell.

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Cell wall of fungi is made up of a chemical substance called chitin. The reserve food materials of fungi are glycogen and oil.

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Fungi have no starch because they have no chlorophyll pigments. So, they are heterotrophs. Heterotrophs are of three types called parasites, saprophytes and symbionts.

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Parasites absorbs food from the living organisms with the help of special root called haustoria. e.g. Cercospora personata. It affects groundnut plants and cause Tikka disease.

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Heterotrophs are of three types called parasites, saprophytes and symbionts. Saprophyte grow up on the dead and decay matters and get food from them. e.g. Rhizopus.

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Some species of fungi living with algae and are mutually benefitted. e.g. Lichen. Some fungi live symbiotically with higher plants roots called Mycorrhizae

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Penicillin (Penicillium notatum), Neomycin, Gentamycin, Erythromycin are some antibiotics obtained from fungi, which cure variable diseases.

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Mushroom contains rich protein and minerals. The most common edible mushroom is Agaricus.
(Button mushroom).

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Fungus like Ashbya gospii and Erymothecium ashbyii are used to produce vitamin B2 (riboflavin). Fungus like yeast contain enzymes invertase and zymase, which ferment the sugar molasses into alcohol.

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Fungi placed as third kingdom in RH Wittekar’s five kingdom classification because absence of chlorophyll and starch.

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Claviceps purpuriya is the hallucinogenic fungi causes greatest damages to the frustrated youth by giving unreal, extraordinary lightness and hovering sensations

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Aspergillus species cause allergy to children while Cladosporium protects against allergy. Fungus like yeast contain enzymes invertase and zymase, which ferment the sugar molasses into alcohol.

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 Bryophytes are the primitive and simplest group of land plants.
 These are terrestrial and non-vascular cryptogams (they have no vascular tissues like xylem, phloem).

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Queen of medicine is Penicillin, discovered by Sir Alexander Fleming in 1928. Fungi are heterotrophs.

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Water is essential to complete their life cycle, so Bryophyte plants are called amphibians of the Plant Kingdom.

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General Characters of Bryophytes:

 Sexual reproduction is oogamous type
 The male sex organ is antheridium, which produces antherozoid.
 The female sex organ is archegonium which contains an egg.

Explanation

Zygote is the first cell which develops into sporophytic generation and produce haploid spore (n) by meiosis. Spore is the first cell of the gametophytic generation.

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Class I: Hepaticae (e.g. Riccia)

• These are lower forms of bryophytes. They are simple in structure than moss.

• Protonemal stage is absent. Sporophyte is very simple and short lived.

Explanation

Class–II: Anthocerotae

• Gametophyte is undifferentiated-thallus, rhizoids are unicellular and unbranched.

• Protonemal stage is absent. Sporophyte is differentiated into foot and capsule only.

Explanation

Economic Importance of Bryophytes:

 Bryophytes prevent the soil erosion.
 Sphagnam can absorb large amount of water. Hence, it is used by the gardeners in nursery
 Peat is a valuable fuel like coal obtained from Sphagnum.

Explanation

Sphagnum moss was once used in disposable diapers, because it soaks liquid well. Sphagnum is used in horticulture.

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Pteridophytes are the first true land plants with xylem and phloem. Hence it is called vascular cryptogams.

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General Characters of Pteridophyte:

The main plant body is sporophytes, which is the dominant phase, differentiated into true root, stem and leaves. Sporophytes reproduce by means of spores. Spores are produced in sporangium. The sporangia bearing leaves are called sporophyll.

Explanation

Ferns are used as ornamental plants. The rhizome and petioles of the Dryopteris yield the vermifuge drug.

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Lycopodium, is known as club moss. Equisetum is known as horse tail. The sporocarp of Marsilea (water fern) is used as food by tribal people.

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Gymnosperm are naked seed plant, i.e. the ovule is not enclosed by ovary. Gymnosperms have two phases in its life cycle. (Sporophytic and Gametophytic)

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General Characters of Gymnosperms:

 Plant body is sporophyte dominant which is differentiated into root, stem and leaf.
 They have well developed vascular tissues. (xylem and phloem)
 The water conducting tissue is tracheid. Food conducting tissue is sieve cell
 They have cone on which sporangia and spores are produced.

Explanation

Economic Importance of Gymnosperms:

 Woods of many conifers are used in the paper industries. e.g. Pinus, Agathis
 Conifers are the sources of soft wood for construction, packing and plywood industry e.g. Cedrus, Agathis

Explanation

Turpentine is an essential oil used for paint preparation extracted from the resin of Pinus. It is also used medicinally to get relief from pain and bronchitis etc.,

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 Seeds of Pinus gerardiana are edible.
 Ephedrine is an alkaloid extracted from Ephedra. It cures asthma and respiratory problems.
 Araucaria bidwillii is an ornamental plant.

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The term ‘Angiosperm ’is derived from two Greek words, i.e. ‘Angio’ which means box or closed and ‘sperma’ which means seed.

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Angiosperms are called flowering plants. In this group more than 4,00,000 living species are found. They occupy every habitat on earth except extreme environment. (extreme hot and cold conditions).

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Xylem contains vessel, tracheid, xylem parenchyma and xylem fibre. Phloem contains sieve tubes, phloem parenchyma, companion cells and phloem fibres.

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Characteristic features of monocotyledons:

 Seed has only one cotyledon.
 Plants have fibrous root system, leaves with parallel venation.
 Flowers are trimerous and not differentiated in to calyx and corolla.
 Pollination occurs mostly by wind.
 E.g. Grass, Paddy, Banana.

Explanation

Characteristic features of
Dicotyledons:

 Seed has two cotyledons.
 Plants have tap root system, leaves with reticulate venation.

Flowers are tetramerous or pentamerous. Calyx and corolla are well differentiated.

 Pollination occurs mostly by insects.
 E.g. Bean, Mango, Neem

Explanation

Acalypha indica (Kuppaimeni) belongs to the family Euphorbiaceae. The paste obtained from the leaves of this plant is used to cure the burns on the skin.

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Aegle marmelos (Vilvam) belongs to the family Rutaceae. The unripe fruit of this tree is used to treat indigestion. It is used to cure chronic, diarrhoea and dysentery.

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Phyllanthus amarus (Keezhanelli) belongs to the family Euphorbiaceae. The entire plant is used for the treatment of jaundice. It gives additional strength to human liver and used to treat other liver disorders.

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Aloe vera belongs to the family Liliaceae. Leaves of this plant is used to cure piles and inflammations on the skin. It cures peptic ulcer.