Protists and Slime Molds – Vocabulary (Chapter 1-6)

Protists: Overview

• Protists are eukaryotic organisms, meaning they have a nucleus. They also possess membrane-bound organelles inside their cells. They are usually unicellular, but some can be multicellular or form colonies.
• Major distinction in this week’s content: classification by mode of nutrition, not strictly by kingdom lines.
• There are three main nutritional categories for protists:
  • Animal-like protists (protozoa): heterotrophs that digest their food inside the body (like us).
  • Plant-like protists: autotrophs that make their own food via photosynthesis (like algae).
  • Fungus-like protists: heterotrophs that digest externally (decompose food outside, then absorb nutrients).
• A fifth group, myxotrophs, describes organisms that can be both autotrophic and heterotrophic (mixotrophs).
• Some examples of groups discussed:
  • Amoebas (pseudopodia), dinoflagellates, diatoms, green algae (Chlorophyta), and ciliates (e.g., Paramecium), plus protozoans like Trypanosoma.
  • Slime molds: plasmodial slime molds and cellular slime molds (fungus-like protists).
• Real-world relevance mentioned in lecture:
  • Algae (plant-like protists) contribute to a large portion of world oxygen production.
  • Dinoflagellates can cause red tide events and produce bioluminescence in ocean waters.
  • Some protists are disease vectors or parasites (e.g., Trypanosoma causes African sleeping sickness, transmitted by tsetse flies).

Nutritional modes of protists: three main categories

• Animal-like protists (protozoa)
  • Heterotrophs: obtain food by ingesting other organisms; digestion occurs intracellularly.
  • Locomotion is often used for feeding and movement once food is found.
• Plant-like protists (algae)
  • Autotrophs: photosynthesize to make their own food.
  • Pigments involved include chlorophylls; examples include diatoms, green algae, and dinoflagellates (the latter can be mixotrophic at times).
• Fungus-like protists (saprotrophs)
  • Heterotrophs: external digestion (secreted enzymes break down food outside the body), then absorption of nutrients.
• Myxotrophs (mixotrophs)
  • Organisms that can switch between autotrophy and heterotrophy depending on conditions (e.g., some dinoflagellates).

Fungus-like protists: Slime molds

• Two main types:
  • Plasmodial slime molds (plasmodia)
  • Have a nucleus that divides many times, but the cells do not separate; form a large multinucleate mass called a plasmodium.
  • When food or water becomes scarce, plasmodium differentiates into sporangia (reproductive structures) that release spores.
  • Spores are dormant until conditions become favorable for germination.
  • Cellular slime molds
  • Cells divide nuclei but remain separate; under stress, individual cells aggregate to form a colony.
  • The colony differentiates into a structure called a fruiting body (the lecturer referred to as a formation that releases spores).
• Both slime molds are heterotrophic and fungus-like in their ecology, but differ in cellular organization and reproduction.

Animal-like protists: locomotion and examples

• Three main locomotive modes in animal-like protists:
  1) Pseudopodia (temporary cytoplasmic extensions used for movement and feeding)
  2) Flagella (long whip-like tails used for swimming)
  3) Cilia (many short, hair-like projections used for swimming and feeding)
• Amoebas (pseudopodia)
  • Types of pseudopodia:
  • Lobed pseudopodia (sarcodina/rhizopodium)
  • Thin, spike-like pseudopodia called axopodia
  • Terminology note: axopodia are thin pseudopodia; foraming organisms like radiolarians and related groups may display them.
• Flagellates
  • Flagellum: a whip-like tail used for propulsion.
  • Example: Trypanosoma (a genus that includes species responsible for African sleeping sickness; discussed as Trypanosoma in the lecture).
• Ciliates
  • Cilia: numerous short projections surrounding the cell used for movement and feeding.
  • Example: Paramecium.

Plant-like autotrophs: body forms, pigments, and locomotion

• Plant-like protists are categorized by body form, presence of flagella, and photosynthetic pigments they contain.
• Diatoms
  • Pigments: chlorophyll a and c.
  • Cell wall: silica-based structure.
  • Locomotion: limited or essentially none.
  • Ecological note: extremely abundant algae; major producers of global oxygen.
• Green algae (Chlorophyta)
  • Pigments: chlorophyll a and b (similar to land plants).
  • Cell wall: cellulose.
  • Locomotion: flagellated forms exist among green algae.
  • Relationship: closely related to land plants.
• Myxotrophs (mixotrophs)
  • Example: some dinoflagellates are mixotrophic (capable of photosynthesis and ingesting prey).
• Dinoflagellates
  • Pigments: chlorophyll a and c.
  • Locomotion: two flagella for movement.
  • Light emission: bioluminescence (emits light in response to stimulation).
  • Ecological note: some cause red tide events; some dinoflagellates are bioluminescent.
  • Additional feature: many have paired flagella and a characteristic the lecture notes describes as bioluminescence; some are mixotrophic.
• Visualized point: red tides are associated with certain dinoflagellates and can involve significant ecological impacts.

Axopodia, actinopodia, and skeletal features

• Axopodia vs actinopodia
  • Axopodia: slender, spike-like pseudopodia used by certain protists for prey capture and movement.
  • Actinopoda: a group that features radiating projections called axopodia; the lecture notes mention actinopodia in relation to axopodia and radiating projections.
• Skeletons
  • Some groups with axopodia have skeletons made of silica or chitins, depending on the lineage.
  • The lecture notes mention silica or chitin as materials for the skeletons of these radiating-projection protists.
• Takeaway: pseudopodial structures (axopodia) and their skeletal material are key diagnostic features for some protist groups.

The dinoflagellate table and quick Q&A (concept checks from the lecture)

• Green algae (Chlorophyta) table entry
  • Locomotion: 2? (The class discussion concluded that many green algae have flagella, i.e., flagellated locomotion; some non-motile forms exist.)
  • Correct answer highlighted: flagella (i.e., they can move with a flagellum/flagella).
  • Nutrition: autotrophs (photosynthetic).
  • Relation to other groups: not fungus-like; green algae are protists but more closely related to plants.
• Slime mold question: plasmodium vs cellular slime mold
  • If the cells are separating from each other, that corresponds to cellular slime mold.
  • Conversely, plasmodial slime mold shows a single multinucleate plasmodium with nuclei dividing without cell separation.
• Which protist has nucleus dividing but no cell division, forming sporangia that release spores?
  • Plasmodial slime mold.
• Which organism lacks a relying locomotion form in a certain diagram and is flagged as “none” or shows non-motility?
  • Diatoms are often non-motile; many are silica-skeletoned and non-malfunctioning in terms of locomotion.
• Which group lacks a locomotion form and is represented as having no movement?
  • Diatoms typically lack locomotion; their cell walls and ecology reflect non-motile forms.
• Which protist is characterized by a pattern with cilia instead of flagella in the given image?
  • The organism with cilia (Paramecium-like) does not belong to the flagellate group in that particular image.
• Which organisms glow (bioluminescence) and what causes red tides?
  • Dinoflagellates glow via bioluminescence; red tide events are caused by certain dinoflagellates.
• Which organism uses pseudopodia as locomotion and feeding method with lobed pseudopodia (sarcodina/rhizopodium) or axopodia?
  • Amoebas use pseudopodia; lobed pseudopodia correspond to sarcodina/rhizopodium; axopodia are thin pseudopodia used by other protists.
• Which protist can be found in blood and causes African sleeping sickness? What is the vector?
  • Genus Trypanosoma (e.g., Trypanosoma sp.); transmitted by the tsetse fly.
• What are axopodia, and which groups feature them? What are their skeletal materials?
  • Axopodia are thin pseudopodia; actinopoda (radiolarians and related groups) are associated with axopodia; their skeletons can be made of silica or chitin.

Connections, significance, and practical implications

• Ecological roles
  • Algae (plant-like protists) contribute a major share of the world’s oxygen via photosynthesis.
  • Diatoms, in particular, are key primary producers in aquatic ecosystems due to their abundance and photosynthetic capacity.
• Environmental phenomena
  • Dinoflagellates can cause red tide events, impacting marine life and coastal environments; some are bioluminescent, creating striking oceanic displays.
• Human health and disease
  • Amoeboid and flagellate protists can be pathogenic or vector-borne (e.g., Trypanosoma spp. cause sleeping sickness; tsetse flies as vectors).
• Evolutionary context
  • Green algae are closely related to land plants, sharing key pigments (chlorophylls a and b) and cellulose-based cell walls, highlighting evolutionary links to terrestrial photosynthetic life.
• Study strategies highlighted in the session
  • Use a table to categorize protists by: locomotion type, nutrition, and key example groups.
  • Recognize morphological features: flagella, cilia, pseudopodia, and silica/chitin skeletons as diagnostic characteristics.
  • Remember representative examples for quick recall during exams (e.g., Paramecium for ciliates, Amoeba for pseudopodia, Trypanosoma for disease relevance, Diatoms for silica shells).

Key terms and quick glossary

• Eukaryote: organism with a nucleus and membrane-bound organelles.
• Autotroph: organism that makes its own food via photosynthesis.
• Heterotroph: organism that consumes organic material for food.
• Mixotroph: organism capable of both autotrophy and heterotrophy.
• Plasmodium (plasmodial slime mold): multinucleate, single cellular mass without cytokinesis; forms sporangia to produce spores.
• Fruiting body: structure produced by slime molds that releases spores.
• Cellular slime mold: cells divide nuclei and remain separate; aggregate to form a fruiting structure.
• Pseudopodium (pseudopodium, plural pseudopodia): temporary cytoplasmic extension used for movement and feeding.
• Lobed pseudopodium: a type of pseudopodium with broad, lobed extensions (sarcodina).
• Axopodium (axopodia): thin, spike-like pseudopodia.
• Flagellum (flagella): whip-like locomotive appendage.
• Cilium (cilia): numerous short locomotory appendages around a cell.
• Chlorophyll a, b, c: photosynthetic pigments used by various protists.
• Diatom: a siliceous-shelled alga; important oxygen producers.
• Dinoflagellate: a dinophyte with two flagella; some are bioluminescent and cause red tides; mixotrophic in some cases.
• Axopodia vs actinopodia: pseudopodial projections; actinopoda typically have silica/chitin skeletons; axopodia are thin projections.
• Trypanosoma: genus of protozoa causing African sleeping sickness; transmitted by tsetse flies.

Note on LaTeX formatting in this document: When a mathematical expression or symbol is used, it is formatted with LaTeX syntax and enclosed in double dollar signs, for example: a, b, 2, 3, ext{chlorophyll } a, or ext{chlorophyll } a ext{ and } b as appropriate.