Biology Protista and Chrysophytes

Protista

• A diverse kingdom of single-celled eukaryotes
• Forms a link between plants, animals, and fungi
• Primarily aquatic organisms
• Possesses a well-defined nucleus and membrane-bound organelles
• Some have flagella or cilia
• Reproduce asexually and sexually through cell fusion and zygote formation
• Nutrition varies: parasitic, ingestive, photosynthetic, saprophytic, mixotrophic
• Includes photosynthetic phytoplankton, non-photosynthetic zooplankton, and disease-causing parasites
• Food reserves: starch, glycogen, paramylon, chrysolaminarin, and fat

Chrysophytes

• Includes diatoms and golden algae (desmids)
• Found in freshwater and marine environments
• Microscopic and float passively in water currents (plankton)
• Majority are photosynthetic
• Diatoms are primary producers in oceans
• Diatom cell walls consist of two overlapping shells, fitting like a soap box
• Walls are made of silica, making them indestructible
• Diatom shells accumulate at the bottom of water reservoirs, forming diatomaceous earth
• Diatomaceous earth is used in polishing, filtration of oils and syrups

Dinoflagellates

• Primarily marine and photosynthetic
• Appear yellow, green, brown, blue, or red due to varying pigment proportions
• Cell wall has stiff cellulose plates on the outer surface
• Most have two flagella: one longitudinal and the other transverse
• Red dinoflagellates, like Gonyaulax, multiply rapidly, causing "red tides"
• Toxins released by red tides can kill marine animals, like fish
• Exhibit bioluminescence due to photogenic granules in cytoplasm
• Some species are consumed by mussels
• Also known as "night light"

Euglenoids

• Freshwater organisms found in stagnant water
• Have a protein-rich layer called pellicle instead of a cell wall, allowing flexibility
• Possess two flagella: one short and one long
• Photosynthetic in sunlight
• Behave like heterotrophs in the absence of sunlight, preying on smaller organisms
• Pigments similar to those in higher plants
• Example: Euglena

Slime Moulds

• Saprophytic protists, also called "fungus animals"
• Move along decaying twigs and leaves, engulfing organic matter
• Form an aggregation called plasmodium under suitable conditions
• Plasmodium can grow and spread over large areas
• During unfavorable conditions, the plasmodium differentiates and forms fruiting bodies
• Fruiting bodies bear spores at their tips
• Spores have true walls and are highly resistant, surviving for years
• Spores are dispersed by air currents
• Example: Physarum