(ROBERT P. GERDON)
Humans classify almost everything, including each other. This habit can be quite useful. For example, when talking about a car someone might describe it as a 4-door sedan with a fuel injected V-8 engine. A knowledgeable listener who has not seen the car will still have a good idea of what it is like because of certain characteristics it shares with other familiar cars. Humans have been classifying plants and animals for a lot longer than they have been classifying cars, but the principle is much the same. In fact, one of the central problems in biology is the classification of organisms on the basis of shared characteristics. As an example, biologists classify all organisms with a backbone as “vertebrates.” In this case the backbone is a characteristic that defines the group. If, in addition to a backbone, an organism has gills and fins it is a fish, a subcategory of the vertebrates. This fish can be further assigned to smaller and smaller categories down to the level of the species. The classification of organisms in this way aids the biologist by bringing order to what would otherwise be a bewildering diversity of species. (There are probably several million species ‑ of which about one million have been named and classified.) The field devoted to the classification of organisms is called taxonomy [Gk. taxis, arrange, put in order + nomos, law].
(Father of taxonomy)
THALLOPHYTA ( gk. Thallos–undiffierentiate. -plant)
It is division of plantae in which the plants do not have a well differentiates body design.
- Simple body .The body design is simple and is often called thallus.
- Reproduction organs .they are unicellular and non jacketed.
- Embryo stage.Absent.
4.Vascular tissue: absent
They are THALLOPHYTA which are capable of manufacturing their own food through photosynthesis.
Algae are most aquatic .only a few of them occur in moist terrestrial habitat.
- The common forms of algae are thread – like ( branched or unbranched) filament and parenchymatous thallus.
- Algae are of three main group — green ,red and brown .Red and brown colour are due to presence of large amount of accessory photosynthetic pigment in addition to chlorophyll.
- Mucilage . The plant body is covered over by mucilage
- Nutrition. Photosynthetic
- Cell wall. It contain cellulose.
- Reserve food. It is generally starch or some related chemical.
Example . Ulothrix, spirogyra, ( both unbranched filaments) ; Cladophora, chara, ( branched filament) ,ulva( flat,parenchymatons thallus).
GAMETOPHYTE AND SPOROPHYTE
Dicot and Monocot