Chapter 28: Protists

Flashcards covering the classification, characteristics, and examples of various protist groups including Excavata, SAR, Archaeplastida, and Unikontka.

Protist

The informal name of the group of mostly unicellular eukaryotes that are no longer considered a single kingdom due to recent advances in systematics.

Photoautotrophs

Protists that contain chloroplasts and perform photosynthesis.

Heterotrophs

Protists that absorb organic molecules (decomposers) or ingest larger particles (hunters).

Mixotrophs

Protists that combine photosynthesis and heterotrophic nutrition (ingestive or absorbtive).

Flagellates

Protists that move by using one or more flagellae.

Ciliates

Protists that move by the coordinated movement of cilia.

Amoebae

Protists that move and feed by means of pseudopodia, which are cellular extensions that bulge from the cell surface.

Zygotic life cycle

A life history where haploid cells transform into gametes, which then fuse to form zygotes; an example is Plasmodium.

Alternation of generations

A life cycle that produces two types of multicellular organisms ($n$ and $2n$), common in many algae and all land plants.

Micronucleus

A tiny nucleus found in Ciliates; in the sexual process of conjugation, individuals exchange haploid micronuclei to result in genetic variation.

Macronucleus

A large nucleus found in Ciliates that controls everyday functions.

Conjugation

A sexual process in ciliates where individuals exchange a haploid micronucleus to result in genetic variation.

Excavata

A supergroup of protists that include those with modified mitochondria and unique flagella, such as Diplomonads, Parabasilids, and Euglenozoans.

Diplomonads

Excavates that have two nuclei and mitochondria but lack plastids; an example is Giardia lamblia.

Parabasalid

Excavates with flagella arranged in clusters at the anterior end, an undulating membrane, and an axostyle.

Axostyle

A rod-like structure found at the opposite end from the tuft of flagella in Parabasalids.

Euglenozoans

A group of Excavata whose main feature is a spiral or crystalline rod of unknown function inside their flagella.

Kinetoplast

A single, large mitochondrion containing a circular disk of DNA found in Kinetoplastids.

Trypanosma gambiensis

A parasite belonging to the Kinetoplastids that causes African Sleeping Sickness.

SAR

A highly diverse supergroup of protists defined by DNA similarities, formed by the merger of three clades: Stramenopiles, Alveolates, and Rhizarians.

Stramenopiles

A clade in the SAR supergroup whose members have numerous fine, hairlike projections on their flagella, usually paired with a shorter, smooth flagellum.

Diatoms

Unicellular algae (photoautotrophs) with glass-like walls composed of silica; they are a major component of phytoplankton.

Diatomaceous earth

Massive accumulations of fossilized diatoms in marine sediments used in toothpastes and filter media.

Brown Algae (Phaeophyta)

Multicellular, mostly marine seaweeds containing carotenoid pigments that give them a brownish/olive color.

Algin

A gel-forming substance from the cell wall of brown algae used to thicken processed foods like ice cream and ranch dressing.

Golden Algae

Biflagellated protists named for their yellow and brown carotenoids; most are unicellular but some are colonial.

Alveolates

A clade of the SAR supergroup characterized by alveoli, which are small membrane-bound cavities under the plasma membrane.

Dinoflagellates

Aquatic photoautotrophs and mixotrophs with internal cellulose plates and two flagella that cause them to spin.

Red Tide

A phenomenon caused by certain dinoflagellates that produces a neurotoxin leading to massive invertebrate and fish kills.

Sporozoites

The infectious stage of Plasmodium injected by a mosquito vector that travels to the host's liver cells (hepatocytes).

Circumsporozoite protein

A protein on the surface of Plasmodium sporozoites that allows them to attach to receptors on hepatocytes.

Merozoites

Daughter cells of Plasmodium that multiply in the liver, rupture into the bloodstream, and penetrate red blood cells.

Apicoplast

A nonphotosynthetic plastid found in Plasmodium.

Balantidium coli

A large ciliated protozoan that can infect humans, often using pigs as a reservoir host, causing ulcers in the colon.

Rhizarians

A monophyletic clade of the SAR supergroup, most of which are amoebas with thread-like pseudopodia.

Radiolarians

Marine protists with delicate internal skeletons made of silica and pseudopodia known as axopodia used to capture microorganisms.

Foraminiferans (Forams)

Protists named for their porous, multi-chambered shells called tests made of calcium carbonate.

Cercozoans

A large group of amoeboid and flagellated protists that feed with threadlike pseudopodia, common in marine, freshwater, and soil ecosystems.

Chlorarachniophytes

A small group of mixotrophic cercozoans that have four membranes surrounding their plastids as a result of secondary endosymbiosis.

Archaeplastida

A supergroup that includes red algae, green algae, and land plants.

Red Algae (Rhodophyta)

Protists that are usually multicellular and reddish in color due to the accessory pigment phycoerythrin.

Phycoerythrin

An accessory pigment in red algae that gives them their reddish color.

Green Algae

Protists named for their green chloroplasts containing chlorophyll $a$ and $b$, divided into chlorophyta and charophyta.

Charophyta

The group of green algae that is most closely related to land plants.

Spirogyra

A filamentous charophyte green algae featuring a spiral arrangement of chloroplasts.

Unikonts

A supergroup that includes protists closely related to fungi and animals, characterized by lobe-shaped pseudopodia.

Plasmodial Slime Molds

Amoebozoans that form a mass called a plasmodium, which is a coenocytic, multi-nucleated single cell feeding stage.

Coenocytic

A state where cells go through mitosis but not cytokinesis, resulting in an acellular organism that looks like a single large multi-nucleated cell.

Cellular Slime Molds

Amoebozoans that form multicellular aggregates where cells are separated by their membranes, such as Dictyostellium discoideum.

Entamoeba histolytica

A parasitic amoebozoan that causes amebic dysentery and lives in the colon as a trophozoite.

Opisthokonts

A major group within the Unikonts that includes animals, fungi, and several groups of protists.