Phylum Pyrrophyta

It includes dinoflagellates. These are next to diatoms as producers in ocean. The blooms of Gonyaulax and Gymnodinium cause red tides since the cells are present in such a large quantity that they colour the water. Some dinoflagellates are bioluminescent. It means they emit light. Their phosphorescence causes glowing bodies in the dark

e.g., Noctiluca, Gonyaulax, Pyrocystis, Pyrodinium.

Important features

(i) Unicellular, motile, photosynthetic organisms.

(ii) Body is enclosed in a cellulose wall divided into plates which give an armoured appearance.

(iii) Have two unequal flagella; one lies in a longitudinal direction and the other lies transversely in a furrow between the wall plates. Due to presence of two flagella at right angles to each other, the dinoflagellates show peculiar spinning movement. Hence, they are called “whirling whips.”

(iv) Organisms reproduce asexually only. Sexual reproduction is almost unknown.

(v) About 1,000 species are known. Most of these are marine.

Phylum Euglenophyta

It includes Euglena-like flagellates which have plant characteristics (chlorophyll) in addition to some animal characteristics. They ingest food particles and carry on photosynthesis.

Important features

(i) Mostly unicellular and free living, found in fresh water, ditches or in damp soil.

(ii) Have a pellicle instead of a cellulose cell wall. Pellicle is flexible and allows a change in shape.

(iii) Have a long, whip like flagella inserted at the front end in a cavity. It helps Euglena pull through the water. 

(iv) Have a light sensitive red spot called eye spot near the flagellum base that enables it to move towards or away from light.

(v) The dominant photosynthetic pigment is chlorophyll, therefore are green in appearance.

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