WEEK 1
SUBJECT: BIOLOGY
CLASS: SS2
TOPIC: CLASSIFICATION OF PLANTS
Plants are generally classified based on three (3) major criteria.
These are:
1. Botanical Classification
2. Agricultural Classification
3. Classification Based on Life cycle
{Let’s discuss each way of plants classification}
1: Botanical Classification
Plants can be generally classified through the Botanical method and the use of binomial system (-a way of giving two names to an organism).
Botanical classification is a technique used in classifying plants according to their groups in the kingdom plantae.
Kindom plantae is divided into five (5) groups, namely:
A. Schizophyta (Bacteria).
B. Thallophyta (The algae and Fungi).
C. Bryophyta (The Liverworts and Mosses).
D. Pteridophyta (The Ferns).
E. Spermatophyta (These are the seed-bearing plants) spermatophyte consists of gymnosperms (Non-flowering plants) and the angiosperms (Flowering plants).
{We consider the features of each of the Groups quickly}
A. FEATURES OF SCHIZOPHYTA (BACTERIA)
-They are microscopic and non-cellular.
-No organized nucleus (Procaryotic cells).
-The cell wall does not contain cellulose.
-They reproduce by binary fussion.
-Bacteria exist in various shapes.
-Common shapes of bacteria are: Cocci, Vibrios, Bacilli, and Spirilla. (Check the diagram below and illustrate the same in your note book)
B. FEATURES OF THALLOPHYTA (ALGAE & FUNGI)
ALGAE
-They are simple plants without root, stems and leaves.
-All algae have chlorophyll. Some have blue, yellow, brown, and red-pigments which mask the chlorophyll. {Red algae-Rhodophyta, Green algae-Chlorophyta, Brown algae-Phaecophyta}
-Some are unicellular, while few are multi-cellular. E.g. seaweeds are large.
-They are mainly aquatic; few are in damp soils and shady places. E.g. Spirogyra, Anabaena, and Sargassum.
FUNGI
-They are non-green plants.
-They are simple multi-cellular plants.
-The body is not differentiated into root, stem and leaves.
-The vegetative body (hypha) is collectively known as mycelium.
-Reproduction is by means of spores.
-The cell wall is composed of cellulose and chitin.
-Carbohydrates are stored in form of glycogen as in animal.
-They are either saprophytic or parasitic. E.g. Mucor, Rhizopus, Yeast, and Fusarium, Aspergillus, Penicillium, and Mushroom.
C. FEATURES OF BRYOPHYTA (MOSSES AND LIVERWORTS)
-They are non-vascular multi-cellular organisms.
-Have chlorophyll as the only photosynthetic pigment.
-They are terrestrial but live in moist environment.
-The body is differentiated into stem –like and leaf-like structures. They lack true roots, stem and leaves. They lack vascular tissue and therefore unable to transport food and materials round the body.
-The leaves of some are spirally arranged on the stem.
Asexual reproduction is by spores, while sexual reproduction is by gametes. Water is needed in sexual reproduction hence they are regarded as alternation of generations.
-Some are thalloid in form e.g. Liverworts. Examples are Marchantia sp. (liverwort) and Funaria hygrometrica (a moss).
D. FEATURES OF PTERIDOPHYTA (FERNS)
-The body is differentiated into true roots, stem and leaves with well-developed vascular bundles comprising xylem and phloem. The young leaves are coiled.
-They are non-flowering, non-seed producing plants.
-The stem is a rhizome.
-Reproduction is by means of spores.
-Asexual reproductive organ is a heart-shaped prothallus.
-Water is needed for sexual reproduction (prothallus).
-They are mainly terrestrial, with a few aquatic members. E.g. are Dryopteris, Cyclosorus, Platycerium, Phymatodes, are terrestrial while Nephrolepis, Salviniaoblongata, and Azolla are aquatic members.
(Check the diagram below and illustrate the same in your note book)
The FERN (Dryopteris)
E. FEATURES OF SPERMATOPHYTA (GYMNOSPERMS & ANGIOSPERM)
I. GYMNOSPERMS- THE ‘NON-FLOWERING PLANTS’
-They are large plants with well-developed vascular bundles with true roots, stem and leaves.
-The leaves are green in colour, small scaly and needle-like.
-They have cones where naked seeds are formed because there is no ovary. Fruit is not formed.
-They are terrestrial in habitat. E.g. are whistling pine (Casuarina sp.) and Cycas.
II. ANGIOSPERM –‘THE FLOWERING PLANTS’
-They possess true flowers for sexual reproduction.
-Well-developed true roots, stems and leaves are present.
-Well-developed vascular bundles are present.
-Seeds and fruits are produced after fertilization. Seeds are enclosed in an ovary.
-They are terrestrial, but few are aquatic. E.g. are Oil palm tree, Goat weed, Mango tree and Maize.
NOTE: ‘ANGIOSPERM’ can be further sub-divided into two (2) classes according to the number of seeds leaves (-cotyledons). These are:
-Dicotyledonous plants -having two seed leaves
-Monocotyledonous plants –having one seed leaf
END OF BOTANICAL CLASSIFICATION OF PLANTS
(NOW THAT WE’VE CONSIDERED BOTANICAL CLASSIFICATION OF PLANTS, LET’S LOOK AT THE REMAINING TWO WAYS OF CLASSIFICATIONS OF PLANTS, BEFORE THE END OF THE THIS WEEK LESSON.)
2. AGRICULTURAL CLASSIFICATION
Agricultural classification includes the following:
-Fibres: e.g. cotton, hibiscus, hemp and sisal.
-Latex: e.g. rubber.
-Root and Tuber crops: yams, cassava, potatoes and cocoyam.
-Cereals: rice, maize, wheat, guinea corn etc.
-Fruits: e.g. citrus fruits, pawpaw, mangoes, pineapples etc.
-Legumes: e.g. beans, soya beans, cowpea and groundnuts.
-Beverages and drugs: e.g. coffee, cocoa, sugar cane, kola nut.
-Spices: e.g. pepper and ginger.
-Vegetables: e.g. tomato, okro, carrot, lettuce etc.
-Oil Plants: e.g groundnut, melon, coconut, soyabean etc.
3. CLASSIFICATION BASED ON LIFE CYCLE
These include the following:
-Ephemerals: They are plants that complete their life cycle in few weeks, e.g. water leaf.
-Annuals: these are plants that complete their life cycle in one year, e.g. maize, tomatoes, rice, garden egg, and yam.
-Biennials: these include flowering plants that complete their life cycle in two years: e.g. onions and carrots.
-Perennials: plants that complete their life cycle in three years, e.g. mangoes, and oranges, cocoa and kola nut etc.
You can watch the same explanation of the topic here-https://youtu.be/Oprm7OKI1Ak?si=mQBgtSBiQsybp5vd
ASSIGNMENT QUESTIONS
Q1. State four (4) differences between Monocotyledonous and Dicotyledonous plants
Q2. State three (3) differences between Gymnosperm and Angiosperm
Q3. Draw a well-labeled diagram of Spirogyra as an example under Thallophyta
(WEEK 1 ONLINE QUICK QUIZ: Attempt here-https://forms.gle/Psb4eXqqyv79iwjPA)
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