Chapter 17 Bio Lab Review

Protists: Diversity, Structure, and Function

Introduction to Protists

Protists are a diverse group of mostly unicellular eukaryotic organisms that do not fit into the plant, animal, or fungal kingdoms. They are classified based on their similarities in structure, nutrition, and life cycles. Protists are traditionally grouped as plant-like (algae), fungus-like, and animal-like (protozoans) protists.

Plant-like Protists ("Algae")

Phylum Chlorophyta (Green Algae)

• Volvox (slide and wet mount)

  • Nutritional Mode: Phototroph (photosynthetic)

  • Unique Characteristics: Forms spherical colonies; each colony consists of numerous flagellated cells embedded in a gelatinous matrix. Daughter colonies are produced asexually inside the parent colony.

  • Individuals vs. Colonies: Individual cells can exist, but typically observed as colonies.

• Spirogyra (slide, wet mount, poster)

  • Nutritional Mode: Phototroph

  • Unique Characteristics: Spiral-shaped chloroplasts visible in cells.

  • Conjugation: A form of sexual reproduction where filaments align and exchange genetic material through conjugation tubes.

Phylum Bacillariophyta (Diatoms)

• Diatoms (slide, wet mount, poster)

  • Nutritional Mode: Phototroph

  • Unique Characteristics: Possess a cell wall (test) made of silica; remains accumulate as diatomaceous earth.

Phylum Rhodophyta (Red Algae)

• Polysiphonia (slides, blocks)

  • Nutritional Mode: Phototroph

  • Unique Characteristics: Red color due to phycobilin pigments; multicellular marine algae.

Phylum Euglenophyta

• Euglena (slide, wet mount)

  • Nutritional Mode: Mixotroph (can photosynthesize and ingest food)

  • Unique Characteristics: Possess flagella for movement; flexible pellicle instead of a rigid cell wall.

Fungus-like Protists

Phylum Myxomycota (Plasmodial Slime Molds)

• Plasmodial Slime Mold (Petri dish)

  • Nutritional Mode: Absorption (decomposers)

  • Unique Characteristics: Multinucleate, amoeboid mass called a plasmodium; moves by cytoplasmic streaming.

Phylum Oomycota (Water Molds)

• Saprolegnia (slide)

  • Nutritional Mode: Absorption

  • Unique Characteristics: Cell wall composed of cellulose (not chitin); aquatic, filamentous organisms.

Animal-like Protists ("Protozoans")

Overview

• Divided into four major groups based on locomotion: pseudopodia, flagella, cilia, and non-motile forms.

• Nutritional Mode: Heterotrophs (ingest or absorb food).

Group 1: Pseudopodia

• Phylum Sarcodina/Rhizopoda (Amoeba)

  • Locomotion: Pseudopodia (extensions of cytoplasm)

  • Unique Characteristics: Presence of nucleus and food vacuoles.

• Phylum Foraminifera (Forams)

  • Locomotion: Threadlike pseudopodia through pores in calcium carbonate shell (test)

  • Unique Characteristics: Shells contribute to limestone formation.

• Phylum Actinopoda (Radiolarians)

  • Locomotion: Thin, stiff pseudopodia

  • Unique Characteristics: Shells made of silicon dioxide.

• Phylum Sarcodina (Entamoeba histolytica)

  • Unique Characteristics: Causes amoebic dysentery; found in fecal smears.

Group 2: Flagella

• Phylum Zoomastigina (Trypanosoma rhodesiense)

  • Locomotion: Flagella and undulating membrane

  • Unique Characteristics: Causes African sleeping sickness.

• Phylum Pyrrophyta (Dinoflagellates)

  • Locomotion: Flagella

  • Unique Characteristics: Some species cause red tides, which can lead to shellfish poisoning.

• Kingdom Diplomonadida (Giardia lamblia)

  • Locomotion: Flagella

  • Unique Characteristics: Causes giardiasis; found in fecal smears.

• Kingdom Parabasalid (Trichonympha)

  • Locomotion: Flagella

  • Unique Characteristics: Symbiont in termite guts, aids in cellulose digestion.

Group 3: Cilia

• Phylum Ciliophyta (Ciliates)

  • Locomotion: Cilia

  • Examples:

    • Paramecium: Has anterior and posterior ends, cilia for movement, macronucleus, micronucleus, oral groove (food intake), contractile vacuole (osmoregulation), and trichocysts (defense).

    • Vorticella: Sessile, attached to substrate, cilia around oral region.

    • Stentor: Sessile, vase-shaped, cilia for feeding.

  • Reproduction: Paramecium can reproduce by conjugation (exchange of genetic material).

  • Response to Stimuli: Paramecium can react to negative stimuli (e.g., vinegar) by reversing ciliary beat.

Group 4: Non-motile

• Phylum Apicomplexa (Apicomplexans)

  • Locomotion: Non-motile in mature form

  • Examples: Plasmodium vivax, Plasmodium falciparum (cause malaria)

  • Transmission: By Anopheles mosquito

  • Life Cycle:

    1. Sporozoites enter host blood via mosquito bite

    2. Schizonts develop in liver

    3. Schizogony releases merozoites

    4. Merozoites infect red blood cells, become trophozoites

    5. Trophozoites mature, produce more merozoites (repeat)

    6. Some trophozoites become gametocytes (micro- and macrogametocytes)

    7. Gametocytes taken up by mosquito

    8. Gametes mature in mosquito, form zygote

    9. Zygote forms oocyst

    10. Oocyst releases sporozoites, cycle repeats

Summary Table: Major Protist Groups

Group	Phylum/Example	Locomotion	Nutritional Mode	Unique Features
Plant-like	Chlorophyta (Volvox, Spirogyra), Bacillariophyta (Diatoms), Rhodophyta (Polysiphonia), Euglenophyta (Euglena)	Flagella (Euglena, Volvox), Non-motile (Spirogyra, Diatoms)	Phototroph, Mixotroph (Euglena)	Colonies, spiral chloroplasts, silica/cellulose walls, red pigments
Fungus-like	Myxomycota (Slime Mold), Oomycota (Saprolegnia)	Amoeboid (slime mold), Non-motile (water mold)	Absorption	Multinucleate plasmodium, cellulose cell wall
Animal-like	Sarcodina (Amoeba), Foraminifera, Actinopoda (Radiolarians), Zoomastigina (Trypanosoma), Pyrrophyta (Dinoflagellates), Diplomonadida (Giardia), Parabasalid (Trichonympha), Ciliophyta (Paramecium), Apicomplexa (Plasmodium)	Pseudopodia, Flagella, Cilia, Non-motile	Heterotroph	Shells, undulating membrane, conjugation, parasitism

Key Terms and Definitions

• Phototroph: Organism that obtains energy from light.

• Mixotroph: Organism capable of both photosynthesis and heterotrophy.

• Pseudopodia: Temporary cytoplasmic projections for movement and feeding.

• Flagella: Long, whip-like structures for locomotion.

• Cilia: Short, hair-like structures for movement and feeding.

• Conjugation: Sexual process involving exchange of genetic material.

• Schizogony: Asexual reproduction by multiple fission, common in Apicomplexa.

• Test: Hard shell of some protists (e.g., foraminifera, diatoms).

Examples and Applications

• Red tides: Caused by dinoflagellate blooms, can produce toxins harmful to marine life and humans.

• Malaria: Caused by Plasmodium species, transmitted by mosquitoes, major global health concern.

• Diatomaceous earth: Used as a filtration aid, mild abrasive, and insecticide; composed of fossilized diatom remains.

• Symbiosis: Trichonympha lives in termite guts, aiding in cellulose digestion.

Additional info: Academic context and definitions have been added to clarify and expand upon the original lab exercise instructions, ensuring the notes are self-contained and suitable for exam preparation.