Biological Sciences Lecture on Protists

Announcements / Reminders

• Upcoming Assignments:
  • RRQs 10-12 due by 12 PM (noon) on Tuesday, April 22.
  • Module 6 activity & discussion post due by 11:59 PM on Tuesday, April 8:
  • Access information on Biology Student Resources Canvas site.
  • Upload the table to the Assignments folder in Biol 211 Canvas site.
  • Post the Module 6 thread under the Discussion tab in Biol 211 Canvas site.
• Exam #3:
  • Will include many taxon names and life cycles.
  • Recommend to start learning them now! Date: Tuesday, April 22

Seminar Series: Biological Sciences

• Guest Speaker: Amanda Kahn, PhD
  • Topic: The secret lives of sponges: Understanding ancient animals at their own pace.
• Biography Highlights:
  • Focus on movement of food and carbon in deep-sea ecosystems.
  • Research includes deep-sea sponges from various regions.
  • Educational background includes Biology and Chemistry at CSU Bar Bay, Master's in Marine Science, and a PhD in Ecology.
  • Joined Moss Landing Marine Laboratories & San Jose State University in 2019 as Assistant Professor.
• Suggested Reading: "Surf, Sand, and Stone" by Keith Heyer Meldahl
• Contact Information: Dr. Houng-Wai Tsai at CSULB for more details.

Review of Previous Topics

• Finished discussing prokaryotes, including different groups of Bacteria and Archaea.
• Introduced viruses and key questions surrounding their origins.
• Discussed the evolution of eukaryotic cells and their life cycles.

Introduction to Protists

• Defining Protists: All eukaryotes except plants, animals, and fungi.
  • Most eukaryotic lineages are classified as protists.
  • Deepest nodes in eukaryote phylogeny are poorly resolved.

Today's Goals: Explore Major Clades of Protists

1. Archaeplastida
2. Excavata
3. SAR Clade
4. Unikonta

• Detailed exploration of named groups within each clade.

Major Clades of Protists

Archaeplastida

• Defined by plastids from primary endosymbiosis, using chlorophyll a (chl a)

• Four Main Groups:

  • Red Algae
  • Green Algae
  • Glaucophytes (sister taxon to other Archaeplastida)
  • Land Plants

• Glaucophytes:

  • Unicellular, freshwater “algae”, unique in having a peptidoglycan layer in chloroplast membranes.

• Red Algae (~6000 species):

  • Contain both chl a and phycoerythrin (gives red color).
  • Mostly marine, known for diverse life cycles.
  • Some examples include:
  • Nori (used in sushi)
  • Agar (used for lab cultures)
  • Coralline red algae (important for coral reefs).

• Green Algae (~8000 species):

  • Not a clade, paraphyletic group, includes chlorophytes and charophytes.
  • Contains chlorophyll a and b, found in various habitats.
  • Examples include:
  • Chlamydomonas (unicellular)
  • Volvox (colonial)
  • Ulva (multicellular).

Excavata

• Best understood through DNA analysis, primarily unicellular.

• Characteristic features:

  • Feeding groove present in some taxa.

• Diplomonads & Parabasalids:

  • Sister taxa.
  • Diplomonads: mucus-producing, include Giardia lamblia (causes diarrhea).
  • Parabasalids: include Trichomonas vaginalis (causes STIs).

• Euglenozoa:

  • Defined by having flagellae and a crystalline rod.
  • Typically unicellular and diverse in nutrition; can be photosynthetic or heterotrophic.

SAR Clade

• A larger clade, divided into three groups: Stramenopiles, Alveolates, and Rhizarians.
• Stramenopiles:
  • Characterized by two different flagella.
  • Includes:
  • Diatoms: major contributors to photosynthesis, producing silicon dioxide shells, forming diatomaceous earth.
  • Brown Algae: e.g., giant kelp, important in marine ecosystems.

Alveolates:

• Features membrane-bounded sacs (alveoli).
• Includes:
  • Dinoflagellates: important for coral symbiosis and harmful algal blooms.
  • Apicomplexans: obligate parasites like Plasmodium (causes malaria), Toxoplasma (affecting behavior).

Rhizarians:

• Unified by long, thin pseudopodia for movement and feeding.
• Includes:
  • Foraminiferans: calcareous skeletons, useful in geology.
  • Radiolarians: silica skeletons, host symbiotic algae.

Unikonta

• Cells usually with a single flagellum when present.
• Major groups include:
  • Amoebozoans: e.g., slime molds, tubulinids, and parasitic entamoebas.
  • Opisthokonts: includes fungi and animals, recognizable by the position of their flagellum.
  • Slime Molds: can be plasmodial (large, multinucleate) or cellular (aggregating amoebae).

Essential Vocabulary

• Important Terms:
  • Phytoplankton, harmful algal blooms, chlorophyll (a, b), colonies.
  • Taxa: foraminiferans, ciliates, Euglenozoa, etc.
  • Lifecycle types: alternating generations, haplontic and diplontic cycles.

Study Questions

1. Identify major clades of protists and their subtaxa.
2. Describe important protists that are pathogens.
3. Compare and describe different eukaryotic lifecycles.
4. Explain the distinctions between sexual reproduction and reproduction in ciliates.