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

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

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

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

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

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

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

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

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

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

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

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:

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

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

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

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

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

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

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

Eukaryotes Dinoflagellates This is exactly what is happening in Fig. 26.13 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

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

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

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

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

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

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

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)

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

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

Hypotheses for the earliest stages of biological diversification:

Protists Highly diverse genetically and phenotypically Eukaryotes Protists Highly diverse genetically and phenotypically

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

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

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

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

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)

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

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

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

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

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.

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

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.