NIS - BIOLOGY Lecture 93 – Lecture 94 Introduction to Protists Ozgur Unal 1

Protists 2  Protists are classified more easily by what they are not than by what they are.  Protists are:  not animals  not plants  not fungi..  The Kingdom Protista includes more than 200,000 known organisms.  All protists are eukaryotes.  Some produce asexually (by mitosis) and some exchange genetic material during meiosis.

Protists 3  Protists are divided into three groups according to the way they obtain their nutrients:  Animal-like protists (protozoa)  Plantlike protists  Funguslike protists Animal-like protists:  Aka protozoans..  Heterotrophs..  Usually ingest bacteria, algae or other protozoans..  Example: Amoeba is a unicellular protozoa

Protists 4 Plantlike protists:  Commonly referred to as algae..  Can be unicellular or multicellular..  Example: The giant kelp Funguslike protists:  These are similar to fungus because they absorb their nutrients from other organisms.  These organisms are not classified as fungi because they contain centrioles.  Fungus and funguslike protists also differ in the composition of their cell wall.

Habitats of Protists 5  Protists typically are found in damp or aquatic environments, such as decaying leaves, damp soil, ponds, streams and oceans.  They live in symbiotic relationships.  Microsporidia are microscopic protozoans that cause disease in insects.  What benefit can we get from microsporidia?  Green algae live in the hair of a sloth.  What type of symbiotic relationship does algae+sloth represent?

Origin of Protists 6  Remember endosymbiotic relationship?  Some scientists think that mitochondria and chloroplast found in some eukaryotes (including protists) were once individual organisms.  Protists might have been the first eukaryotes to appear billions years ago.  Check out Figure 19.3!!  Notice that all of the protists have a common ancestral eukaryotic cell.