Kingdom Platae: Classification And Characteristics.

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Lesson Note
Subject: Biology
Topic: Classification of Living Things
Sub Topic: Kingdom Plantae
Lesson Objectives: At the end of the lesson, learners should be able to:

State the characteristic features of the kingdom Plantae and give Specific examples of representative organisms.

Lesson Discussion

KINGDOM: PLANTAE

The plant kingdom considered of three main divisions (Phyla). These are:
(a) Thallophyta e.g Green, brown, red algae
(b) Bryophyta e.g Liverworts and Mosses
(c) Tracheophyta e.g vascular plants

Thallophyta
This group can be further be subdivided into three groupings. These are:
i. Rhodophyta (Red algae)
ii. Chlorophyta (Green algae)
iii. Phaecophyta (Brown algae)

Charactersitics of Thallophyta
i. These are simple microscopic plants
ii. Some are unicellar, e.g Chlamydomonas, while others are multicellular, e.g Spirogyra.
iii. These are simple aquatic plants
iv. They have cellular cell walls.
v. Algae are mainly autotrophic plants, i.e they can synthesize their own food
vi. Algae are filamentous and the cells are not differentiated into tissues
vii. Examples are the single free living algae like Chlamydomonas or in form of filaments, e.g spirogyra or in colonies e.g volvox.

Characteristics of Bryophyta
i. They are complex, multicellular green plants
ii. Their cells are differentiated into tissues
iii. They lack true roots, stems and leaves but have structures resembling roots, stems and leaves.
iv. They are non-vascular plants
v. They are usually found growing in moist places
vi. Some bryophytes are terrestial while others are aquatic
vii. Examples are mosses and Liverworts.
Tracheophyta
This division is made up of vascular plants. This division is grouped into two sub-divisions which include:
(a) Pteridophyta
(b) Spermatophyta

Charactersitics of Pteridophyta
i. They are multicellular and vascular green plants
ii. They are non-flowering plants.
iii. They have true roots, stems and leaves
iv. They have mainly terrestial plants while few aquatic
v. They are non-seed producing plants
vi. Example is the ferns and it includes dryoptens, felimas and water ferns.

Charactersitics of Spermatophyta
i. They are multicellular, seed producing flowering plants
ii. They are vascular plants and have well developed vascular tissues
iii. They have true roots, stems and leaves
iv. They reproduce sexually and do not need water for reproduction
v. They are mainly terrestial green plants.
Spermatophyta can be divided into two major classes. These are Gymnosperms and Angiosperms

(a) Gymnosperms
Charactersitics
i. These are plants with naked seeds
ii. They do not bear flowers
iii. They have true roots, stems and leaves
iv. The seeds are borne on special structures called cones.
v. They are vascular green plants
vi. Examples are pine and cycads, gingkos and conifers.

(b) Angiosperms
Charactersitics
i. They are the most complex green flowering plants
ii. They are vascular plants
iii. They have well developed and complete flowers
iv. They are seed plants with seeds enclosed in the fruit.
v. They are mainly terrestial plants.

Divisions of Angiosperms
Angiosperms can be subdivided into three classes according to the number of seed leaves (cotyledons). These are;
i. Dicotyledonous plants
ii. Monocotyledonous plants

Dicotyledonous plants
Charactersitics
i. They bear seeds which have two seeds leaves or cotyledons
ii. The vascular bundles of each item are arranged in a regular pattern
iii. Their floral parts exist in groups of four or five.
iv. The leaves have veins arranged in branched network
v. Examples are mango, orange, cowpea, groundnut, balsam plant etc.

Monocotyledonous plants
Charactersitics
i. They bear seeds which have only one seed leaf
ii. The vascular bundles of the stem are scattered
iii. Their floral parts exist in groups of three or multiples of three
iv. Their leaves have veins running parallel to one another.
v. Examples are maize plants, rice, oil palm and guinea grass.

Modifications of leaves

The leaves of some plants are modified for various purposes. Such modifications are:
i. For food storage: e.g Onion, Garlic
ii. Leaf tendrills e.g Gloriosa
iii. Leaf spines e.g Cactus, Optimal, Euphorbia
iv. Leafhooks e.g Bignonia
v. Vegetative propagation e.g Bryophyllum
vi. Animal traps e.g Venus flytrap, Nepenthes or pitcher plants. Uticularia or Bladderworts, Sundew, Butterwort, Pinguicula.
vii. Protective scale leaves e.g Onions, shallots canna.

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