1. Protists Domain Eukarya 2007-2008 Domain Bacteria Archaea Eukarya
Common ancestor

2. Living Small
Even a low-power microscope can reveal a great variety of organisms in a drop of pond water
Protist is the informal name of the group of mostly unicellular eukaryotes
Advances in eukaryotic systematics have caused the classification of protists to change significantly
Protists constitute a polyphyletic group, and Protista is no longer valid as a kingdom

3. Which of these organisms are prokaryotes and which are Eukaryotes?

4. General characteristics
Classification criteria
eukaryotes
not animal, plant or fungi
The organisms in most eukaryotic
lineages are protists, and
Most protists are unicellular

5. Structural and Functional Diversity
Protists exhibit more structural and functional diversity than any other group of eukaryotes
Though most protists are unicellular, there are some colonial and multicellular species
Single-celled protists can be very complex, as all biological functions are carried out by organelles in each individual cell

6. dinoflagellates & ciliates
Great Diversity
dinoflagellates & ciliates
brown algae & diatoms
euglenoids
red algae
green algae
miscellaneous?

7. Be sure to know the 4 different Clades and 2 examples from each
Be sure to know the 4 different Clades and 2 examples from each! Check out page

8. Problems with Protist Classification
Too Diverse!
doesn’t reflect any evolutionary relationship amongst all kingdom members
paraphyletic
Euglenozoa
Animals
Streptophyta
(includes land plants)
Choanoflagellida
Fungi
Chlorophyta
Rhodophyta
Stramenopila
Alveolata
Archaea
Bacteria
Something’s not right here!

9. Protist Diversity The full spectrum of modes of life
from unicellular to multicellular
autotrophic to heterotrophic
asexual to sexual reproduction
pathogenic to beneficial
sessile to mobile

10. Nutrionally Diverse Photoautotrophs, which contain chloroplasts
Heterotrophs, which absorb organic molecules or ingest larger food particles
Mixotrophs, which combine photosynthesis and heterotrophic nutrition

11. Protist Diversity Plant-like Protists autotrophs, photosynthesis
Euglena
algae
diatoms

12. Protist Diversity Animal-like Protists heterotrophs, predators Amoeba
Paramecium with food vacuoles stained red
Protist Diversity
Animal-like Protists
heterotrophs, predators
Amoeba
Paramecium
Stentor
Amoeba ingesting a Paramecium

13. Protist Diversity Parasitic & pathogenic Protists malaria Giardia
trypanosomes
Plasmodium
Giardia
Trypanosoma

14. Protist Diversity Beneficial & necessary Protists phytoplankton
small algae + diatoms
much of the world’s photosynthesis
produces ~90% of atmospheric oxygen
zooplankton
heterotrophic protists + animals
key ecological role at base of marine food web

15. Mobility
How Protists move
flagellum
cilia
pseudopod

16. Evolution of Protist
There is now considerable evidence that much protist diversity has its origins in endosymbiosis
Endosymbiosis is a relationship between two species in which one organism lives inside the cell or cells of the other organism (the host)

17. Theory of Endosymbiosis
mitochondrion
internal membrane system
aerobic bacterium
Ancestral eukaryotic cell
Eukaryotic cell with
mitochondrion
Paramecium & symbiont Chlorella
photosynthetic bacterium
chloroplast
Eukaryotic cell with chloroplasts

18. Any Questions??