Animal-like protist

• Protists are simple eukaryotic organisms that cannot be categorized as animals, plants, or fungi
• Protists are heterotrophs
• Protists are unicellular organisms classified based on their mode of locomotion (cilia, flagella, pseudopodia)
• Protists are mostly found in damp environments like freshwater, marine, and moist terrestrial habitats
• Many species of protists are free-living, while some are parasitic, living in the bloodstream of their host
• ~10,000 species of protists are symbiotic in or on animals/plants or other protozoans
• Heterotrophs ingest/engulf small food particles & digest it inside food vacuoles
• Protists life activities are carried out within the limits of a single plasma membrane
• Some protozoans can detect light with eyespots
• Many protists form cysts when conditions become unfavorable and resume metabolic activity when conditions become favorable
• Freshwater protozoa have contractile vacuoles to remove excess water
• Sarcodina (Amoeba) cytoplasm has two divisions: Ectoplasm and granular, Inner endoplasm
• Sarcodina move by means of pseudopodia
• Gaseous exchange occurs through the cell membrane of Sarcodina (Amoeba)
• Numerous Amoeba species can inhabit the human intestinal tract
• Flagellata (Zooflagellates)are unicellular organisms that may be free-living or parasitic
• In Flagellata, nutrition can be holozoic or saprotrophic, reserved food is stored as glycogen
• Flagellata mostly reproduce by binary fission because sexual reproduction is rare
• Sporozoa (Apicomplexans) are parasites of animals, some causing dangerous diseases to humans
• Non-motile parasites disseminate as tiny infectious cells called sporozoites
• Most apicomplexans have intricate life cycles with both sexual and asexual stages
• Ciliophorans (Ciliates)are the largest group of protozoans that move via cilia
• Ciliophorans can reproduce asexually by mitosis & sexually by conjugation
• Ciliates have several highly specialized structures
• Most ciliates have a well-developed contractile vacuole
• Cilia sweep food into the oral groove where the mouth is located at the bottom
• In ciliates, food enters a short tube called gullet into food vacuoles where it's digested and waste leaves through an anal pore
• Some ciliates have a strengthened clear, elastic covering of cell membrane called pellicle
• Balantidium coli is the only ciliate that parasitizes humans, causing dysentery