This document discusses protists and their evolution and classification. It describes how endosymbiosis led to the development of organelles in eukaryotic cells from prokaryotic ancestors. Protists are the most diverse eukaryotic kingdom and are classified based on evolving criteria including DNA analysis. Some protists like Chlamydomonas are useful for studying the origins of multicellularity and processes like sex determination.

1. Eukaryotes - Protista
BIOL 1407
Ebeling

2. Learning Objectives
1. Describe the characteristics common to all protists
2. Explain how endosymbiosis is involved with the evolution of
multicellular eukaryotic organisms from prokaryotic
ancestors
3. Understand why the protists are the most diverse eukaryotic
kingdom
4. Describe the criteria used to classify protists

3. Origins of eukaryotes: division of labor
Eukaryotic cells
contain membrane
bound organelles.
What is the origin of
these organelles?
Golgi apparatus
cell membrane
cytoplasm
endoplasmic
recticulum
(ER)
nucleus
cell wall
chloroplast

4. Membrane infolding hypothesis
Section 15.2 Fig. 15.7

5. The endosymbiont theory
Section 15.2 Fig. 15.8

6. Endosymbiont Theory
Lynn Margulis 1970

8. Why are protists important?
● Phytoplankton
● Zooplankton
Fig. 38.4

9. How are protists classified?
Protist classification is a work in
progress!
Traditionally, taxonomists classified
them based on organisms they most
resembled.
DNA analysis is leading to changes in
how biologists classify protists.
Classification is changing so that it is
based on common evolutionary
lineage.

11. plant-likefungus-likeanimal-like

17. http://www.youtube.com/watch?v=
GY_uMH8Xpy0

24. Some protists are helpful in studying origins of multicellularity
Chlamydomonas--unicellular green algae that can reproduce
sexually.
Used to study:
● the evolution of sex
● how individual sex is determined
● how cells of opposite sex recognize each other
Choanoflagellates--single cell or
colonies. These are a sister group
to animals.
Used to study:
● how cells
interact with
each other
● how cells
communicate
with each other
Dictostelium--”Dicty” cellular
slime mold.
Used to study:
● cell movement
● chemotaxis (moving
toward a stimulus)
● cell differentiation