WSU BIO 1501 Chapter 10: Protists

Protists Overview

• Protists
    - Eukaryotic organisms that are neither plants, animals, nor fungi.
    - Can be classified as single-celled, multicellular, or colonial.
    - Exhibit a diverse array of feeding methods, movement patterns, and reproductive strategies.
    - Not classified as a monophyletic group.

Monophyletic Group

• Definition:
    - A group of organisms that share a common ancestor and include all of its descendants.

Supergroups in Eukarya

• The six recognized supergroups include:
    - Excavata
    - Chromalveolata
    - Rhizaria
    - Archaeplastida
    - Amoebozoa
    - Opisthokonta

Types of Protists

• Unicellular
    - Defined as organisms that consist of a single cell, which carries out all life processes necessary for survival.

• Multicellular
    - Organisms composed of more than one cell; these cells are typically organized into specialized tissues, organs, and organ systems.

• Colonial
    - Comprising genetically identical cells that live in close association, often for mutual benefit, yet retain individual functions.

Body Plans of Specific Protists

1. Amoeba
     - Body plan: single-celled

2. Diatoms
     - Body plan: single-celled

3. Slime Molds
     - Body plan: colonial

4. Volvox
     - Body plan: colonial

5. Red Algae
     - Body plan: multicellular

Classification of Protists by Nutrition

• Plant-Like Protists
    - Commonly referred to as algae.
    - Possess chloroplasts and are autotrophic (photosynthetic).
    - Lack specialized tissues and organ systems.
    - Important for marine and freshwater food chains.

• Fungi-Like Protists
    - Heterotrophic organisms that feed on decaying matter (detritivores).
    - Reproduce via spores.

• Animal-Like Protists (Protozoa)
    - Heterotrophic and consume other organic matter.
    - Usually motile, equipped with appendages aiding in movement.

Examples of Specific Protists

• Volvox
    - Phylum: Chlorophyta
    - Mode of reproduction: asexual, colonial body plan
    - Motility: via flagellum

• Spirogyra
    - Body plan: ladder-like, multicellular
    - Reproductive strategy: sexual reproduction via conjugation; non-motile

• Diatoms
    - Phylum: Bacillariophyta
    - Body plan: single-celled, photosynthetic
    - Composition: silica in cell walls
    - Reproduction: asexual via binary fission; non-motile

• Red Algae (Phylum Rhodophyta)
    - Characteristics: plant-like, multicellular or colonial
    - Pigment: phycoerythrin for photosynthesis
    - Mode of life: non-motile except for gametes; exhibits alternation of generations

• Euglena
    - Phylum: Euglenophyta
    - Body plan: single-celled
    - Nutrition: mixotrophic (both photosynthetic and ingestion)
    - Characteristics: flexible pellicle coating, motile via flagella, includes a light-sensitive eyespot

• Plasmodial Slime Molds (Phylum Myxomycota)
    - Characteristics: fungus-like, plasmodial form
    - Mode of reproduction: via spores and fruiting bodies

• Amoeba (Phylum Rhizopoda)
    - Characteristics: single-celled organism using phagocytosis for feeding
    - Movement: utilizes pseudopodia (false feet) and cytoplasmic streaming

• Foraminifera
    - Appearance: resemble sea shells
    - Characteristics: unicellular; utilize calcium carbonate in tests (shells)
    - Feeding: extend pseudopodia for feeding

Pathogenic Protists

• Trypanosoma
    - Characteristics: unicellular, flagellate
    - Impact: causes pathogenic diseases such as African Sleeping Sickness and Chagas Disease

• Trichomonas Vaginalis
    - Characteristics: zooflagellate, parasite
    - Mode of movement: motile via flagellum
    - Human health: known STI with humans as the only known host

Other Protist Types

• Zooflagellates
    - Definition: Any heterotrophic, animal-like protist that possesses one or more flagella for movement

• Ciliates (Phylum Ciliophora)
    - Description: exhibit various shapes with motile appendages known as cilia

• Paramecium (Phylum Ciliophora)
    - Characteristics: unicellular, heterotrophic
    - Reproductive strategies: reproduces via binary fission; conjugation occurs during reproduction
    - Movement and feeding: utilizes cilia

• Apicomplexans (Phylum Apicomplexa)
    - Characteristics: single-celled, intracellular parasites
    - Diseases: responsible for causing malaria; non-motile

• Toxoplasma Gondii
    - Characteristics: unicellular, intracellular parasite
    - Reproduction: sexual reproduction occurs in the intestines of cats
    - Health implications: harmful to human fetuses

General Characteristics of Protists

• All protists share a common definition: they are eukaryotic organisms.

Mixotrophy and Other Nutritional Strategies

• Mixotrophy
    - Definition: The ability to switch between photosynthesis (autotrophy) and the consumption of other organisms (heterotrophy).
    - Example: Euglena is categorized as a mixotroph.

Classification and Distinctions

• Brown Algae (Phaeophyta)
    - Classification: Large, multicellular seaweeds and kelps belong to this group.

Specialized Structures and Functions

• Amoebas
    - Specialized structures: utilize pseudopodia for movement and feeding.

• Diatoms
    - Cell walls: intricate, glass-like cell walls composed primarily of silica.

Disease-Like Conditions

• Malaria
    - Pathogen responsible: Plasmodium; a non-motile intracellular parasite.

Fungal-Like Distinctions

• Comparison of cell wall composition:
    - Fungi-Like Protists: use cellulose.
    - True Fungi: utilize chitin.

Cytoplasmic Streaming

• Definition: A process that helps in rapidly distributing nutrients, waste products, and organelles throughout the cell.

Volvox as a Model Organism

• Study Importance: Volvox is significant in studies due to its hollow, spherical colonies that exhibit early signs of cell specialization (division of labor).