Algae are both unicellular and multicellular, they are photosynthetic, each has chlorophyll and other photosynthetic pigments
Euglenoids: only unicellular, found in aquatic environment, use flagella to move, no cellwall, can eat food in surrounding when there is no light, decomposers
Diatoms: shells made of silica, unicellular, pigment called carotenoids, are autotrophic, primary food source for organisms, produce a lot of Earth's oxygen
Dinoflagellates: spin in circles using two flagella, create toxins that can kill, some are known to glow
Red, Green and Brown Algae: seaweeds, multicellular aquatic organisms, have different colours, produce oxygen, brown ones have air bladders to float to surface