SSS 1: CLASSIFICATION OF LIVING THINGS (II)

  THE KINGDOM: PLANTAE
The plant kingdom consists of three main divisions. They are:
1. Thallophyta
2. Bryophyta
3. Tracheophyta                          
                       Thallophyta
This group is further subdivided into three parts:
(a) Rhodophyta (Red algae)
(b) Chlorophyta (Green algae)
(c) Phaecophyta (Brown algae)

   Characteristics of Thallophyta
1. They are simple microscopic plants
2. Some are unicellular organisms e.g. Chlamydomonas while others are multicellular organisms e.g. spirogyra
3. They have a thread-like (filamentous) or flat (thallus) body that do not have roots, stems or leaves.

4. They have a cellulose cell wall
5. They can synthesize their own food
6. They have no specialized reproductive organs for reproduction 
Examples: Chlamydomonas (a free-living algae), Spirogyra (filamentous algae), Volvox (they exist in colonies), Sargassum, Ulva etc

     

                           SPIROGYRA 

                      

                         BRYOPHYTA

              Characteristics of Bryophyta

1. They are multicellular green plants

2. They are non- vascular plants

3. Their cells are differentiated into tissues

4. They lack true roots , stems and leaves but have structures that resemble roots, stems and leaves

5. Some bryophytes are terrestrial while some are aquatic

6. They exhibit asexual reproduction by spore formation and sexually by gametes by a process called alternation of generations.  

Examples of Bryophyta: mosses, hornworts, and liverworts

     ALTERNATION OF GENERATION

Alternation of generations means that plants alternate between two different life stages, or generations, in their life cycle; a haploid stage called gametophyte and a diploid stage called sporophyte.

 The terms haploid and diploid refer to the number of chromosomes contained in the cells.

In  alternation of generation, the sporophyte stage is always attached and dependent on the gametophyte stage.

Alternation of generation occurs in Bryophytes (liverworts, mosses and hornwort) and pteridophytes (ferns)

                          Ulva plant

Ulva shows isomorphic alternation of generation in which biflagellate gametes are formed by gametophyte and the sporophyte produces quadriflagellate zoospores.

                     Life cycle of Ulva

           

                  MOSS PLANT

              Life cycle of moss plant 

                    Liverwort - Marchantia

                  Life cycle of liverwort

                          

                         Tracheophyta

They are made up of vascular plants. They are further subdivided into

1. Pteridophyta

2. Spermatophyta

Characteristics of Pteridophyta

1. They are multicellular green plants

2. They are vascular plants

3. They are non-flowering plants

4. They have true roots, stems and leaves

5. They are mainly terrestrial plants while few are aquatic plants

6. They are non-seed producing plants

7. They exhibit asexual reproduction by spore formation and sexually by gametes by a process called alternation of generations. 

Example is the ferns e.g. dryopteris, water ferns etc

                            Fern plant

                 

 Spermatophyta

Characteristics of spermatophyta

1. They are multicellular plants

2. They are mainly terrestrial green plants 

3. They are seed-producing flowering plants

4. They have well developed vascular tissues

5. They have true roots, stems and leaves

6. They reproduce sexually 

Differences between spermatophyta and bryophytes

 Classes of spermatophyta

Spermatophyta are divided into two main classes:

1. Gymnosperms

2. Angiosperms

  Characteristics of Gymnosperms

1. They are plants with naked seeds which are borne on specialized structure called CONES

2. They do not bear flowers

3. They have true roots, stems and leaves

4. They are vascular green plants

Examples: Conifers, pines, cycads, gingkos etc

  Characteristics of Angiosperms

1.