bio202 protists

Unicellular Nature: Most eukaryotes are unicellular organisms.
Complexity: Eukaryotic cells have organelles, making them more complex than prokaryotic cells.
Majority: The organisms in most eukaryotic lineages are protists, most of which are unicellular.

Variety: Protists exhibit greater structural and functional diversity than any other group of eukaryotes.
- Most are unicellular but also include colonial and multicellular species.
Biological Functions: Single-celled protists can be complex, with organelles performing all biological functions.
Reproduction: Some reproduce asexually, while others reproduce sexually or through meiosis and fertilization.

Autotrophs (Plant-like): Perform photosynthesis.
- Examples:
  - Euglena, Diatoms, Dinoflagellates, Red Dinoflagellates, Green Algae.
Heterotrophs (Animal-like and Fungus-like): Ingest food or absorb nutrients.
- Ingestive Example: Amoeba.
- Absorptive Examples: Cellular and Plasmodial slime molds.
Mixotrophs: Utilize both photosynthetic and heterotrophic means of nutrition.

Protist groups are divided into four supergroups based on evolutionary relationships:
- Excavata: Characterized by modified mitochondria and unique flagella. Includes diplomonads, parabasalids, and euglenozoans.
- “SAR” Clade: Includes stramenopiles (Diatoms, Algae), alveolates (Dinoflagellates, Ciliates), and rhizarians.
- Archaeplastida: Contains red algae, green algae, and land plants.
- Unikonta: Includes animals, fungi, and some protists like amoebozoans.

Concept: Much of protist diversity arises through endosymbiosis, a relationship where one organism lives within another.
Mitochondria and plastids evolved from engulfed prokaryotes.
- Mitochondria from an alpha proteobacterium.
- Plastids from cyanobacteria.

Mitochondria evolved first through engulfment of bacteria.
Plastids evolved from photosynthetic cyanobacteria engulfed by heterotrophic eukaryotes.
Resulted in photosynthetic protists like red and green algae.

Excavata group features:
- Modified mitochondria (diplomonads and parabasalids).
- Unique feeding grooves.
Diplomonads: Anaerobic environment, two nuclei, multiple flagella, e.g., Giardia intestinalis.
Parabasalids: Have hydrogenosomes, e.g., Trichomonas vaginalis.

Distinct clade with spiral or crystalline rod in flagella.
Includes diverse organisms, from heterotrophs to mixotrophs (Euglenids and Kinetoplastids).
Kinetoplastids: One mitochondrion with a mass of DNA. Can be free-living or parasitic (e.g., Trypanosoma).

A highly diverse supergroup defined by DNA similarities encompassing:
- Stramenopiles: Hairy and smooth flagella; includes diatoms, golden algae, brown algae.
- Alveolates: Characterized by membrane-enclosed sacs; includes dinoflagellates, apicomplexans, and ciliates.
- Rhizarians: Amoebas with thread-like pseudopodia.

Diatoms: Major components of phytoplankton; silica walls contribute to diatomaceous earth.
Golden Algae: Photosynthetic with unique pigments; often biflagellated.
Brown Algae: Largest and most complex; include multicellular forms like kelps.

Multicellular algae display alternation of generations (haploid/diploid forms).
Complex reproductive cycles involve haploid gametophytes and diploid sporophytes.

Protists as symbionts or producers in their environments.
Example symbionts include dinoflagellates aiding coral polyps.
Parasitic examples such as Plasmodium (malaria).
Photosynthetic Protists: Major contributors of biomass; their health is crucial to aquatic ecosystems.

Protists have a substantial impact on ecological communities, emphasizing their roles as both beneficial symbionts and harmful parasites.