flagella, a short and a long one. Though they are photosynthetic in the presence of sunlight, when deprived of sunlight they behave like heterotrophs by predating on other smaller organisms. Interestingly, the pigments of euglenoids are identical to those present in higher plants. Example: Euglena (Figure .4b) .
. . Slime Moulds Slime moulds are saprophytic protists. The body moves along decaying twigs and leaves engulfing organic material.
Under suitable conditions, they form an aggregation called plasmodium which may grow and spread over several feet. During unfavourable conditions, the plasmodium differentiates and forms fruiting bodies bearing spores at their tips. The spores possess true walls. They are extremely resistant and survive for many years, even under adverse conditions.
The spores are dispersed by air currents. . . Protozoans All protozoans are heterotrophs and live as predators or parasites.
They are believed to be primitive relatives of animals. There are four major groups of protozoans. Amoeboid protozoans: These organisms live in fresh water, sea water or moist soil. They move and capture Figure .
(a) Dinoflagellates (b) Euglena (c) Slime mould (d) Paramoecium (d) (a) (c) (b) their prey by putting out pseudopodia (false feet) as in Amoeba . Marine forms have silica shells on their surface. Some of them such as Entamoeba are parasites. Flagellated protozoans: The members of this group are either free-living or parasitic.
They have flagella. The parasitic forms cause diaseases such as sleeping sickness. Example: Trypanosoma . Ciliated protozoans: These are aquatic, actively moving organisms because of the presence of thousands of cilia.
They have a cavity (gullet) that opens to the outside of the cell surface. The coordinated movement of rows of cilia causes the water laden with food to be steered into the gullet. Example: Paramoecium (Figure .4d) . Sporozoans: This includes diverse organisms that have an infectious spore-like stage in their life cycle.
The most notorious is Plasmodium (malarial parasite) which causes malaria, a disease which has a staggering effect on human population.