1. Chapt. 28 – The Origins of Eukaryotic Diversity
Microbial Diversity
Chapt. 28 – The Origins of Eukaryotic Diversity

2. Single-celled organisms and some non-cellular parasites
What are microbes?
Single-celled organisms and some non-cellular parasites

3. Kinds of microbes Non-cellular, parasitic molecules Prokaryotes
Viruses
Viroids
Prions
Prokaryotes
Domain Bacteria
Domain Archaea
Eukaryotes
Several Kingdoms in Domain Eukarya

4. Carl Woese’s 3 Domains of Life
Based primarily on genetic sequence data; e.g., small subunit ribosomal RNA – present in all organisms

5. Kingdoms of Protists within the Domain Eukarya
Eukaryotes
Kingdoms of Protists within the Domain Eukarya

6. Eukaryotes
Protists
Complex cellular structure – cells with nucleus and other organelles

7. Eukaryotic cell Many membranous organelles… including mitochondria,
which are
common to
all
eukaryotes…
and chloroplasts
(found only in photosynthesizers)

8. Eukaryotes
Protists
Complex cellular structure – cells with nucleus and other organelles
E.g., cilia & flagella aid motility; these cytoplasmic extensions are not homologous with pili or flagella of prokaryotes

9. Eukaryotes Protists Complex cellular structure – cells with
nucleus and other organelles
Nutrition – Absorption, Photosynthesis, or Ingestion

10. Eukaryotes Protists Complex cellular structure – cells with
nucleus and other organelles
Nutrition – Absorption, Photosynthesis, or Ingestion
Reproduction – mostly asexual, but some exchange genetic material

11. exchange of some genetic material across a cytoplasmic bridge
Asexual cell division
(mitosis)
Two modes of protistan reproduction…
Paramecium, a ciliate, reproduces asexually by cell division that results in two daughters identical to the original parent.
Mating in the ciliate Euplotes occurs when genetic material is exchanged across a cytoplasmic bridge – after the exchange, new individuals are formed by cell division that will have gene combinations different from those of either parent cell.
Conjugation:
exchange of some genetic material across a cytoplasmic bridge

12. Sexual, spore-forming cells of a slime mold:
Sexual reproduction via the formation and union of gametes or other haploid cells
(requires meiosis)
See pg. 565 of Campbell & Reece, 7th ed., for an example. Meiosis occurs in the diploid sporangium.
Sexual, spore-forming cells of a slime mold:

13. Eukaryotes
Protists
Complex cellular structure – cells with nucleus and other organelles
Nutrition – Absorption, Photosynthesis, or Ingestion
Reproduction – mostly asexual, but some reproduce sexually
Cysts – resting stages through harsh conditions

14. Protists Arose from endosymbiosis
Eukaryotes
Protists
Arose from endosymbiosis
Compelling evidence for Lynn Margulis’ theory is found in the genetic material of mitochondria & plastids

15. Eukaryotes Macroevolutionary timeline Figure 26.13 Ancestral
prokaryote
Plastids are membrane-bound, specialized organelles, primarily found in plants and plant-like protists.
Macroevolutionary timeline
Figure 26.13

16. endoplasmic reticulum
Eukaryotes
Infolding of plasma
membrane to form
endoplasmic reticulum
and nuclear envelope
Ancestral
prokaryote
Macroevolutionary timeline
Figure 26.13

17. endoplasmic reticulum
Eukaryotes
Infolding of plasma
membrane to form
endoplasmic reticulum
and nuclear envelope
Ancestral
prokaryote
Engulfing of
heterotrophic
prokaryote
Macroevolutionary timeline
Figure 26.13

18. endoplasmic reticulum
Eukaryotes
Infolding of plasma
membrane to form
endoplasmic reticulum
and nuclear envelope
Ancestral
prokaryote
Engulfing of
heterotrophic
prokaryote
Mitochondrion
Macroevolutionary timeline
Figure 26.13

19. endoplasmic reticulum
Eukaryotes
Infolding of plasma
membrane to form
endoplasmic reticulum
and nuclear envelope
Engulfing of
photosynthetic
prokaryote
Plastid
Ancestral
prokaryote
Engulfing of
heterotrophic
prokaryote
Mitochondrion
Macroevolutionary timeline
Figure 26.13

20. Eukaryotes
Dinoflagellates
This is exactly what is happening in Fig when the prokaryote is engulfed and then forms a plastid.
Apicomplexans
Secondary
endosymbiosis
Cyanobacterium
Red algae
Ciliates
Primary
endosymbiosis
Stramenopiles
Heterotrophic
eukaryote
Plastid
Euglenids
Secondary
endosymbiosis
Figure 28.3
Green algae

21. Eukaryotes Figure 28.3 Dinoflagellates Apicomplexans Cyanobacterium
Secondary
endosymbiosis
Cyanobacterium
Red algae
Ciliates
Primary
endosymbiosis
Stramenopiles
Heterotrophic
eukaryote
Plastid
Euglenids
Secondary
endosymbiosis
Figure 28.3
Green algae

22. Eukaryotes Figure 28.3 Dinoflagellates Apicomplexans Cyanobacterium
Secondary
endosymbiosis
Cyanobacterium
Red algae
Ciliates
Primary
endosymbiosis
Stramenopiles
Heterotrophic
eukaryote
Plastid
Euglenids
Secondary
endosymbiosis
Figure 28.3
Green algae

23. Eukaryotes Figure 28.3 Plastid Dinoflagellates Apicomplexans
Secondary
endosymbiosis
Cyanobacterium
Red algae
Ciliates
Primary
endosymbiosis
Stramenopiles
Heterotrophic
eukaryote
Plastid
Euglenids
Secondary
endosymbiosis
Figure 28.3
Green algae

24. Eukaryotes Figure 28.3 Plastid Dinoflagellates Apicomplexans
Secondary
endosymbiosis
Cyanobacterium
Red algae
Ciliates
Primary
endosymbiosis
Stramenopiles
Heterotrophic
eukaryote
Plastid
Euglenids
Secondary
endosymbiosis
Figure 28.3
Green algae

25. Eukaryotes Figure 28.3 Plastid Dinoflagellates Apicomplexans
Secondary
endosymbiosis
Cyanobacterium
Red algae
Ciliates
Primary
endosymbiosis
Stramenopiles
Heterotrophic
eukaryote
Plastid
Euglenids
Secondary
endosymbiosis
Figure 28.3
Green algae

26. Eukaryotes Figure 28.3 Plastid Dinoflagellates Apicomplexans
Secondary
endosymbiosis
Cyanobacterium
Red algae
Ciliates
Primary
endosymbiosis
Stramenopiles
Heterotrophic
eukaryote
Plastid
Euglenids
Secondary
endosymbiosis
Figure 28.3
Green algae
Chlorarachniophytes

27. Eukaryotes Protists Arose from endosymbiosis
Various lineages gave rise to all modern unicellular & colonial protists, as well as all multicellular organisms (some protists, as well as all plants, fungi, and animals)

28. Paraphyletic distribution of protists within a tentative phylogeny of Eukarya
Diplomonadida
Choanoflagellates
Parabasala
Euglenozoa
Cercozoa
Radiolaria
Animalia
Rhodophyta
Chlorophyta
Fungi
Plantae
Alveolata
Stramenopila
Amoebozoa
Ancestral eukaryote
An ancestor and
only some of its
descendents
Figure 28.4

29. “Last Universal Common Ancestor”
Hypotheses for the earliest stages of biological diversification:
“Last Universal Common Ancestor”

30. Hypotheses for the earliest stages of biological diversification:

31. Protists Highly diverse genetically and phenotypically
Eukaryotes
Protists
Highly diverse genetically and
phenotypically

32. Eukaryotes Protists Highly diverse genetically and phenotypically
“Fungus-like” protists
Heterotrophic
Absorption

33. Eukaryotes Protists Highly diverse genetically and phenotypically
“Fungus-like” protists
Heterotrophic
Decomposers
E.g., slime molds
Some “fungus-like” protists are decomposers.

34. Eukaryotes Protists Highly diverse genetically and phenotypically
“Fungus-like” protists
Heterotrophic
Parasitic
E.g., water molds
Some “fungus-like” protists are parasitic.

35. Eukaryotes Protists Highly diverse genetically and phenotypically
“Plant-like” protists
Autotrophic
Photosynthesis

36. Eukaryotes Protists Highly diverse genetically and phenotypically
“Plant-like” protists
Autotrophic
Unicelluar
E.g., Euglena
Some “plant-like” protists are unicellular.
Phytoplankton (unicellular algae & cyanobacteria [prokaryotes] ~ 70% of all photosynthesis)

37. Eukaryotes Protists Highly diverse genetically and phenotypically
“Plant-like” protists
Autotrophic
Multicelluar
E.g., Many
seaweeds
Some “plant-like” protists are multicellular.

38. Eukaryotes Protists Highly diverse genetically and phenotypically
“Animal-like” protists
Heterotrophic
Ingestion

39. Eukaryotes Protists Highly diverse genetically and phenotypically
“Animal-like” protists
Heterotrophic
Free-living
E.g., Some amoebae
Some “animal-like” protists are free-living.

40. Eukaryotes Protists Highly diverse genetically and phenotypically
“Animal-like” protists
Heterotrophic
Parasitic
symbionts
E.g., Giardia
Some “animal-like” protists are parasitic.

41. Eukaryotes Protists Highly diverse genetically and phenotypically
“Animal-like” protists
Heterotrophic
Mutualistic symbionts
E.g., protists of termite guts
Some “animal-like” protists live mutualistically symbiotic lives with other organisms.

42. Eukaryotes Protists Highly diverse genetically and phenotypically
“Animal-like” protists
Heterotrophic
Exhibit slightly more complex behavior than prokaryotes…

43. Predator-prey interaction between ciliates:
Didinium preys upon Paramecium
Figure: 19.32
Title:
Microscopic predator
Caption:
In this scanning electron micrograph, the predatory ciliate Didinium attacks a Paramecium. Note that the cilia of Didinium are confined to two bands, whereas Paramecium has cilia over its entire body. Ultimately, the predator will engulf and consume its prey. This microscopic drama could occur on a pinpoint with room to spare.