ch 27

Overview of Protists

• Seventh Week Discussion: Continuing with the study of protists, a diverse group of eukaryotic microorganisms.

• Upcoming Quiz: Quiz on protist material from the book is scheduled for Sunday night.

• Upcoming Lab: Live demonstrations of protists will be conducted in the lab, showcasing their unique movements and behaviors.

Eukaryotic Classification

• Tree of Life: Divided into three domains: Bacteria, Archaea, and Eukaryotes.

  • Bacteria and Archaea: Simple, single-celled organisms.

  • Eukaryotes: Complex cells with compartments and organelles (e.g., nucleus, mitochondria).

  • Unique Characteristics: Eukaryotic cells are larger and have intricate shapes and structures, making their classification challenging.

Defining Protists

• General Definition: Protists are eukaryotic organisms that are not classified as plants, animals, or fungi.

• Characteristics:

  • Need for Water: Most protists require moist environments to live.

  • Diversity in Structure and Function: Includes various feeding methods and reproductive strategies.

Major Groups of Protists

1. Amorphians, Amoeboids, and Apicomplexa

• Amoeboid Motion: Characterized by pseudopodia for movement (e.g., amoebas).

• Interesting Life Cycles: Examples include slime molds that form slugs and engage in complex behaviors.

• Apicomplexans: Notable for being parasites that can cause diseases in humans (e.g., Plasmodium causing malaria).

2. Archaeoplastida

• Connection to Plants: These protists are the ancestral relatives to plants.

• Algae Types: Includes red algae, green algae, which are essential for photosynthesis on Earth.

  • Carophytes: A type of green algae that contributes significantly to biofuel production.

3. SAR Group

• Components: Incorporates Straminopiles, Alveolates, and Rhizarians.

• Species Diversity: Contains a vast number of protist species with varied living styles and lifecycles.

A. Straminopiles

• Morphological Features: Characterized by two flagella, primarily found in reproductive cells.

• Subgroups:

  • Diatoms: Important photosynthetic organisms with silica cell walls, contributing significantly to ocean photosynthesis.

  • Oomycetes: Water molds that resemble fungi but belong to protists, exhibit fuzzy appearance.

B. Alveolates

• Characteristics: Defined by the presence of alveoli (sac-like structures).

• Subgroups: Includes dinoflagellates, ciliates, and apicomplexans.

  • Ciliates: Use cilia for movement, possess complex feeding mechanisms and multiple nuclei.

  • Dinoflagellates: Some are bioluminescent and can cause harmful algal blooms (red tides).

C. Rhizarians

• Unique Features: Characterized by their amoeboid shape and typically have a hard outer shell called a test.

• Formaminifera: Famous for their shells made of calcium carbonate, contribute to limestone formation.

4. Excavates

• Characteristics: Often parasites lacking typical mitochondrial functions.

• Subgroups:

  • Metamonads: Parasites like Giardia causing gastrointestinal infections.

  • Euglenozoids: Organelle-rich protists capable of photosynthesis or heterotrophy; includes Euglena.

Learning Challenges

• Complexity of Classification: The sheer diversity and complexity of the protist groups make them challenging to study and categorize.

• Learning Strategy: Consistent review and recall of protist characteristics and classifications is essential for navigating the upcoming exam topics.

  • Practice: Recommended to create study tools and engage with material frequently leading up to exams.

Preparation for Exam

• Exam Format: Approximately one-third of the questions will relate to protists, with a focus on classifying them correctly into their respective groups.

• Study Recommendations: Develop a study grid or flashcards to aid in memorization of protists and their characteristics, beneficial for both quizzes and the exam.