Protists belong to the protist kingdom under domain Eukarya. Protists are some of the most basic eukaryotes and are believed to be the ancestors of modern day animals, plants, and fungi. Many protists inhabit aquatic environments or moist terrestrial ones. Protists reproduce using a combination of asexual and sexual reproduction, having complex life cycles. The three main classifications of protists are: protozoa, algae, and molds.
Endosymbiotic Thoery: Theory that eukaryotic organel
les such as mitochondria evolved from ancient, free-living prokaryotes that invaded primitive eukaryotic cells.
Motility: The ability to move.
Pseudopod: A temporary protrusion from the cell membrane.
Flagella: Whip-like projections.
Cilia: Short, whip-like projections.
Protozoa: Animal-like protist.
Algae: Plant-like protist.
Mold: Fungus-like protist.
Protists, believed to be the oldest eukaryotic organisms, may have evolved by endosymbiosis. The endosymbiotic theory postulates that a smaller prokaryotic cell, such as a photosynthetic one, was engulfed by a larger one, forming a symbiotic relationship from which both cells benefited.
Pseudopods look like feet walking. The extension and retraction of pseudopods help move the cell forward.
Flagella are typically significantly longer than cilia. Protists may possess one or more flagellum.
The swaying of cilia determines the direction of movement of the protist.
Protists can reproduce both asexually or sexually.
Ingestive protists take food inside.
Absorptive protists absorb food.
Protozoa are motile heterotrophs and many are unicellular. Protozoa are believed to be the ancestor of animals.
Protozoan movement or lack thereof determines their classification:
Algae are photoautotrophs. Some are unicellular and others are multi-cellular. Some are also motile. They are believed to be the ancestors of plants.
Algae are classified by the origin of their chloroplasts. The four main categorizations are below.
Red and green algae are believed to have evolved before euglenids and dinoflagellates.
Molds are decomposers that directly absorb food or material from their environment. Molds are believed to be the ancestors of fungi. Examples:
Protozoan movement or lack thereof determines their classification: