1. The Kingdom Protista

2. What is a Protist? Eukaryotic Most are unicellular
May include more than 200,000 species
Protists are everything the other kingdoms are not – they are not animals, plants, fungi, or prokaryotes

3. Evolution of Protists – Endosymbiont Theory
Protists were first eukaryotic organisms on Earth
Endosymbiont Theory – theory that eukaryotic cells formed from a symbiosis among several different prokaryotic organisms
Mitochondria, chloroplasts, cilia, and flagella, all began as endosymbionts
Both host and endosymbiont benefited from the relationship
Eventually, the endosymbionts lost ability to live on their own and became organelles.

4. Evolution of Protists – Endosymbiont Theory (continued)
Evidence?
Cyanophora paradoxa, protist whose “chloroplasts” are actually blue-green bacteria that can be removed and can live on their own.
Present-day eukaryotic cells may be descended from more than one organism.

5. Classification of Protists
Biologists do not agree on how best to classify protists
Obtain nutrition
many protists that are heterotrophic considered “animal-like”
other protists that are autotrophic are considered “plant-like”
external digestion (decomposers or parasites) are considered “fungus-like”
These are artificial categories!!
Likely to be reclassified as more research is done on protists

6. How Protists are Classified
are classified by
Animallike
Funguslike
Plantlike
which include
which
which
which
Parasites
Take in food from the environment
Produce food by photosynthesis
Obtain food by external digestion
Decomposers