6: Protists

• Protists are eukaryotic, unicellular organisms, generally microscopic, not animals, plants, or fungi
• Single-celled protists sometimes form colonies with specialized functions
• Volvox is a complex protist that forms colonies, never develops tissues, and has two flagella
• Genetic material within a cell nucleus is characteristic of protists, surrounded by membranes, and possesses mitochondria
• Protists are diverse, with mostly unrelated groups and varied structures, with around 80 different groups of organisms
• Protists reproduce asexually through bipartition, budding, or spores
• Protists reproduce sexually through the exchange of genetic material
• Amoeba are unicellular protists that move and feed by forming pseudopods
• Flagellates are protists with flagella, mostly having one but can have up to 20
• Ciliates are protists with cilia, unique mode of sexual reproduction, two nuclei, and proper mouth
• Foraminifera are protists with shells made of calcium carbonate, significant in the fossil record and oil exploitation
• Protists residing in the rumen of animals aid in digestion
• Protists are classified based on cell shape, presence of scales, and molecular characteristics
• Autotrophic protists use light to produce their own carbon compounds, such as micro-algae and phytoplankton
• Phagotrophic protists are heterotrophs that engulf particles, including protozoa and slime moulds
• Acellular slime moulds have a vegetative form as a shapeless mass of protoplasm called plasmodium, with sporangia and haploid spores
• Protists play a crucial role in the food chain, producing sugars consumed by bacteria, flagellated protozoa, ciliates, and zooplankton
• Phytoplankton, a type of protist, serves as a critical CO2 sink and is essential for the ecosystem
• Certain protists like diatoms, foraminifera, and coccolithophores serve as proxies of climate change due to their significant presence in the fossil record
• Protists play a role in the biological functioning of sewage treatment plants
• Many protozoa are parasitic, causing fatal diseases in plants and vertebrates
• Parasitic amoeba can cause fatal diseases without a vector, such as brain-eating amoebae
• Some protists have complex life cycles involving multiple stages.