Protists: Types and Characteristics

• Protists are eukaryotic organisms that don't fit into the plant, animal, or fungi kingdoms.
• They belong to the kingdom Protista and the domain Eukarya.
• Most protists are unicellular aquatic organisms.
• Eukaryotic cells have a nucleus and membrane-bound organelles, similar to human cells.

Types of Protists

• Protists are categorized into animal-like, plant-like, and fungus-like groups based on their similarities to other eukaryotic kingdoms.

Animal-like Protists

• Animal-like protists are heterotrophs that ingest food to obtain nutrients, similar to animals.
• They are also known as protozoa, meaning "first animals."

Plant-like Protists

• Plant-like protists ar autotrophs that perform photosynthesis to produce sugars and oxygen.
• They are also called protophyta, meaning "first plants."

Fungus-like Protists

• Fungus-like protists are heterotrophs that absorb food for nutrients like fungi.
• Unlike animals and protozoa, they externally digest food before absorbing nutrients.

Endosymbiosis in Protists

• Endosymbiosis involves one cell engulfing another, explaining the origin of chloroplasts and mitochondria in eukaryotic cells.
• Evidence within the Protista kingdom supports the endosymbiosis theory.
• The theory suggests mitochondria were engulfed first, followed by a photosynthetic cell (likely cyanobacteria) becoming the chloroplast.
• Red and green algae (protists) have DNA similar to cyanobacteria, showing an evolutionary link.
• Cyanobacteria is considered an evolutionary ancestor of both red and green algae.

Examples and Importance of Protists

• Protists have diverse examples and significant roles.
• Diatoms
  • Unicellular protists with glass-like cell walls.
  • Over 100,000 species exist.
  • Plant-like and used in nanotechnology due to cell wall structure and small size.

Dinoflagellates

• Found in marine and freshwater environments
• Some species cause red tide by producing toxins that kill aquatic organisms.
• Some have mutualistic relationships with coral, while others are bioluminescent.

Euglena

• Can be autotrophic or heterotrophic depending on resource availability.
• Capable of photosynthesis when sunlight is available.
• Can consume and process nutrients when sunlight is limited.

Protists are eukaryotic organisms categorized into animal-like, plant-like, and fungus-like groups. Animal-like protists are heterotrophs, while plant-like protists are autotrophs. Fungus-like protists are heterotrophs that absorb food for nutrients, similar to fungi.