1. Domain Eukarya Kingdom Protista Phylum Mycetozoa

2. The Organism as a Unit of Life
Looking Back at Bio 115
The Organism as a Unit of Life
Cellular Structure (cell = unit of life)…one or many!
Metabolism = Homeostasis (PSN, Resp, N2fix, ferment, etc.)
Growth = irreversible change in size
Reproduction…failure = extinction
Acclimatization-short term responses = behavior
Adaptation-long term responses = evolution

3. Multicellular Animals
Shifting Kingdoms
Lumpers
Splitters
Plantae
Fungi
Protista 2 3 5 6 8
Bacteria
Archaebacteria
Archezoans
Euglenoids
Chrysophytes
Green Algae
Brown Algae
Red algae
Slime Molds
True Fungi
Bryophytes
Tracheophytes
Protozoans
Myxozoans
Multicellular Animals

4. How Many Kingdoms? Extant 8 Still needs refining! Protista appears 5 3
Multicellular Animals
Myxozoans
Protozoans
Tracheophytes
Bryophytes
True Fungi
Slime Molds
Red algae
Brown Algae
Green Algae
Chrysophytes
Euglenoids
Archezoans
Archaebacteria
Bacteria
Protista
refined 8
Still needs refining!
Protista appears 5 3
Extinct 2 1
Long Time with
Prokaryotes only
Original Cell

5. Mycetozoans “True and Cellular Slime Molds”
Somewhere between protists and fungi
Predatory amoeboid feeding upon bacteria, usually in decaying material
Engulfing feeding
Reproduction via spores
500 species
Two Major Classes:
Myxogastrea (True slime molds: Physarum)
Dictyostelea (Cellular slime molds: Dictyostelium)

6. Physarum polycephalum
True Slime Mold
Haploid (1N) spores germinate in rotting vegetation
Flagellated gametes emerge and undergo syngamy
Diploid (2N) zygote amoeboid cell feeds on bacteria
Mitosis without cytokinesis makes multinucleate plasmodium
Cytoplasm migrates by streaming
Develops into fruiting body undergoing meiosis to make haploid spores

7. Physarum polycephalum
True Slime Mold
This portion of the plasmodium is showing the amoeboid movement of the cytoplasm.
The plasmodium engulfs bacteria by endocytosis into food vacuoles for digestion
Food
Vacuoles
Nuclei
The plasmodium is multinucleate, and each nucleus is diploid (2N).

8. Physarum polycephalum
True Slime Mold
The plasmodium with all of those nuclei and food vacuoles, etc. shows amazingly active cytoplasmic streaming shown in this movie.
The movement involves actin-myosin interactions between microfilaments of actin and myosin proteins bound to organelles.
The movement relies upon Ca2+ and ATP availability.

9. Physarum polycephalum
True Slime Mold
Looking at this sporangium, can you figure out how the specific epithet was inspired?
Sporangium
Sporangiophore
Spores

10. Physarum polycephalum
True Slime Mold
The spores germinate, releasing flagellated gametes.
The gametes unite in syngamy.
The resulting zygote is amoeboid and begins feeding.
Mitoses without cytokinesis enlarges the multinucleate zygote into a full plasmodium.
Spore
Zygote
Gametes

11. Tipula oleraceae or T. paludosa
Adults resemble mosquitoes because they are indeed relatives.
Adults generally do not feed and live for only a few days.
The larval stages are aquatic in some species or lawn soil dwelling in other species.
adult
eggs
adult
larva
pupa

12. Life Cycle of Physarum polycephalum
isogametes
swarm cells
plasmodium
SYNGAMY
no cytokinesis
gametes
zygote
mitosis
germination
asexual
reproduction
mitosis
This is basically the gametic shortcut… spores become gametes… if the mitosis of myxamoebae is not considered equivalent to the production of a multicellular gametophyte.
gametangia
mitosis
differentiation
differentiation
Gametophyte 1N 2N
Sporophyte
myxamoebae
differentiation
differentiation
mitosis
sporangium
germination
mitosis
sporangium
cytokinesis
spores
sporocyte
4 meiospores
MEIOSIS
sporocyte

13. Dictyostelium discoideum
Cellular Slime Mold
This is the spore produced by the sporangium.
Actin rods extend the length of the spore.
It is released into the wind and carried to hopefully-better environments.
There it germinates to produce amoebae.

14. Dictyostelium discoideum
Cellular Slime Mold
The amoebae feed upon bacteria.
When the bacterial supply is gone, one amoeba produces cAMP.
This signals others to join together to form a multicellular pseudoplasmodium (“slug”).
Adenine N
NH2 OH O O- O P
Ribose

15. Dictyostelium discoideum
Cellular Slime Mold
The pseudoplasmodium moves on a slime trail seeking more bacteria.
If bacteria are not found, the plasmodium differentiates into sporangiophore and sporangium.

16. Dictyostelium discoideum
Cellular Slime Mold
The amoebae feed upon bacteria.
When the bacterial supply is gone, one amoeba produces cAMP, signalling the others to join together to form a multicellular pseudoplasmodium (“slug”).
The slug moves on a slime trail seeking more bacteria.
If bacteria are not found, the plasmodium differentiates into sporangiophore and sporangium.
The spores are shed to the wind to disperse the species.