Protists

Endosymbiosis

• Definition: Symbiosis means a mutually beneficial relationship between two parties. In endosymbiosis, a larger cell engulfs a smaller cell, allowing both to survive and work together. This process leads to the formation of chloroplasts and mitochondria.

Three Main Branches of Protists:

1. Plant-like Protists:

   • Phytoplankton

   • Diatoms: Cell walls made of silica.

   • Dinoflagellates: Can cause toxic "red tides."

   • Euglenoids: Autotrophs during the day and heterotrophs in the dark.

2. Animal-like Protists (Protozoans):

   • Have features such as:

     • Flagella: tail-like structures.

     • Cilia: tiny hair-like structures.

     • Pseudopods: false feet for movement.

3. Fungus-like Protists:

   • Heterotrophic and act as decomposers.

   • Different from fungi because they are not made of chitin and can be unicellular or multicellular.

Multicellularity in Protists:

• Algae is a protist but is not as complex as tissues in multicellular organisms.

Reproduction:

• Protists can reproduce both asexually and sexually, with some species capable of both.

Advantages of Protists:

• Plant-like protists are the base of the marine food chain.

• Some are edible and used in foods such as sushi.

Disadvantages of Protists:

• Certain diseases, like malaria, are caused by protozoa.

• Dinoflagellates can lead to harmful red tides.