● `mathtt "Protista"` includes all the `mathtt "unicellular eukaryotes"`. Being eukaryotes, the protistan cell body contains a well defined, membrane bound nucleus and other membrane bound organelles like mitochondria, endoplasmic reticulum, chloroplast, etc.

● The boundaries of this kingdom are not well defined. What may be a ‘photosynthetic protistan’ to one biologist may be ‘a plant’ to another.

● Members of this kingdom include `color{green}"Chrysophytes, Dianoflagellates, Euglenoids, Slime moulds and Protozoans"`.

● Members of Protista are primarily `mathtt "aquatic"`.

● This kingdom forms a `color{green}"link"` with the others dealing with plants, animals and fungi.

● Some motile forms have flagella or cilia.

● Protists reproduce asexually and sexually by a process involving cell fusion and zygote formation.

●` color{Maroon}"Members"`: This group includes `mathtt "diatoms and desmids"`(golden algae ). They are the plant like protists.

● `color{Maroon}"Habitat"`: They are found in fresh water as well as in marine environments.

● `color{Maroon}"Structure"`: They are mostly microscopic and float passively in water currents (plankton). In diatoms, the cell walls form two thin overlapping shells, which fit together as in a soap box.

● `color{Maroon}"Mode of Nutrition"`: Most of them are photosynthetic.

● `color{Maroon}"Ecological Importance"`: Diatoms (which are the major members of the group `mathtt "Phytoplanktons"` are the
`mathtt "chief producers"` in the oceans.

● `color{Maroon}"Economic Importance"`: The cell walls of diatoms are embedded with `mathtt "silica"` and thus the walls are indestructible. Thus, diatoms have left behind large amount of cell wall deposits in their habitat.
`star` This accumulation over billions of years is referred to as `mathtt "diatomaceous earth"`.
`star` Being gritty this soil is used in polishing, filtration of oils and syrups.

●` color{Maroon}"Members"`: This group includes yellow, green, brown, blue or red dianoflagellates whose appearance depend on the main pigments present in their cells.

● `color{Maroon}"Habitat"`: These organisms are mostly marine

●`color{Maroon}"Structure"`: Their cell wall has stiff cellulose plates on the outer surface. Most of them have two flagella; one lies longitudinally and the other transversely in a furrow between the wall plates.

● `color{Maroon}"Mode of Nutrition"` Most of them are photosynthetic.

● `color{Maroon}"Ecological Importance"`: Red dianoflagellates undergo such rapid multiplication that they make the sea appear red (`mathtt "red tides"`).Toxins released by such large numbers may even kill other marine animals such as fishes.

● `color{Maroon}"Example"`:`mathtt "Gonyaulax"` (red dinoflagellate).

● `color{Maroon}"Habitat"`: Most of them are fresh water organisms found in stagnant water.

● `color{Maroon}"Structure"`: Instead of a cell wall, they have a protein rich layer called `mathtt "pellicle"` which makes their body flexible. They have two flagella, a short and a long one.

●`color{Maroon}"Mode of Nutrition"`: They demonstrate a `mathtt "mixotrophic"` mode of nutrition. Though they are photosynthetic in the presence of sunlight, when deprived of sunlight they behave like heterotrophs by predating on other smaller organisms.

● `color{Maroon}"Evolutionary Importance"`: The pigments of euglenoids are identical to those present in higher plants

●`color{Maroon}"Example"`:`mathtt "Euglena"`

● `color{Maroon}"Habitat"`: They are usually found in soil, lawns, and on the forest floor, commonly on deciduous logs.

● `color{Maroon}"Stucture"`:

`color{Maroon}"Under Suitable Conditions"`: They form an aggregation called `mathtt "plasmodium"` which may grow and spread over several feet.

`color{Maroon}"Under unfavourable Conditions"`: The plasmodium differentiates and forms `mathtt "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.

●`color{Maroon}"Mode of Nutrition"`: They are saprophytic protists. The body moves along decaying twigs and leaves engulfing organic material.

● `color{Maroon}"Evolutionary Importance"`: Slime molds were once thought to be fungi, but are now classed as `mathtt "fungus-like organisms"`. This misleading definition is based on physical resemblance to some fungi.

● `color{Maroon}"Example"`: `mathtt "Physarum polycephalum"` (Plasmodial slime molds)

● `color{Maroon}"Mode of Nutrition"`: All protozoans are heterotrophs and live as predators or parasites

●`color{Maroon}"Evolutionary Imortance"`: They are believed to be primitive relatives of animals.

● `color{Maroon}"Members"`: There are four major groups of protozoans.

`color{Violet} "Amoeboid Protozoans"`
`star` These organisms live in fresh water, sea water or moist soil.
`star` They move and capture their prey by putting out `mathtt "pseudopodia"`(false feet) as in Amoeba.
`star` Marine forms have silica shells on their surface.
`star` Some of them such as `mathtt "Entamoeba"` are parasites.

`color{Violet} "Flagellated protozoans"`
`star` The members of this group are either free-living or parasitic.
`star` They have flagella.
`star` The parasitic forms cause diaseases suchas sleeping sickness.
`star` Example: `mathtt "Trypanosoma"`.

`color{Violet} "Ciliated protozoans"`
`star` These are aquatic, actively moving organisms because of the presence of thousands of cilia.
`star` 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.
`star` Example: `mathtt "Paramoecium"`

`color{Violet} "Sporozoans"`
`star` This includes diverse organisms that have an infectious pore-like stage in their life cycle.
`star` The most notorious is `mathtt "Plasmodium"`(malarial parasite) which causes malaria.