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Protists SBI 3U Ms.Zafar What are Protists? • Protists are a diverse group of eukaryotic organisms • Although ancient, they are more recent than monerans • Demonstrate an important evolutionary advancement a discrete, membrane bound nucleus • Most are microscopic and unicellular • Most found in fresh/salt water • More than a 115,000 species Prokaryotes Vs. Eukaryotes • Eukaryotes have DNA in nucleus • Eukaryotes have organelles surrounded by membranes • Eukaryotes are larger • Eukaryotes have many chromosomes • None is more “advanced” than the other 3 Divisions Protists have been divided into 3 groups based on nutritional habits • Plantlike Protists • Animallike Protists • Funguslike Protists Plantlike Protists • 24,000 species • These protists contain chlorophyll • Traditionally called ‘algae’ today, algae refers to any photosynthetic organism that is either unicellular or multicellular without tissues • Plantlike protists divided into euglenoids and algae Euglenoids • Euglenoids obtain nourishment through photosynthesis during the day and heterotrophic in the dark • Two characteristic features: eyespot and flagellum • Eyespot part of the sensory-motor system, used to detect light • Flagellum used to propel organism Euglenoids, continued … • Example: Euglena a green, single-celled, freshwater organism Algae • • • • • • Algae contain chloroplasts Some are single-celled and others are multicellular No tissues Well adapted to wet or moist environments 6 main groups we will discuss 3 3 groups diatoms, dinoflagellates, green algae Algae, continued … • Algae – especially green algae – play an important role in the environment produce 67% of the global supply of oxygen Diatoms • • • • • Single-celled algae Look golden Unique cell wall made of silica Key producers in marine and freshwater ecosystems Example: Cyclotella Dinoflagellates • • • • • Dinoflagellates are single-celled algae Have 2 flagella causes spinning motion Most are photosynthetic, some are heterotrophic Luminescent Grow rapidly if conditions are right! Gonyaulax polyhedron Green Algae • • • • Green Algae are either single-celled or colonial 2 flagella Live in fresh water Ancient green algae modern plants Funguslike Protists • These protists, also referred to as slime moulds • Prefer cool, shady, moist places and are usually found under fallen leaves or on rotting logs • All are heterotrophic most are decomposers • Three groups acellular slime moulds, cellular slime moulds and water moulds Acellular Slime Moulds • Single-celled protists that have many nuclei • Plasmodium wall-less mass of cytoplasm with many nuclei uses pseudopodia to get around • Pseudopodia temporary extension of eukaryotic cell for locomotion Cellular Slime Moulds • Cellular slime moulds are multicellular • Live in fresh water, damp soil or decaying matter Water Moulds • Live in water • Feed on the remains of dead plants and animals • Some may attack crops Iris potato famine
