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Home , Amoeba, Amoeba (genus), Archaeplastida, Brown algae, Ciliate, Dinoflagellate

9/29/14

Biosc 41 Announcements 9/29 Review: History of v Quick review followed by lecture quiz (history & v How long ago is thought to have formed? phylogeny) v What is thought to have been the first genetic material? v Lecture: v Are we ? v Lab: (-like protists) v Most atmospheric comes from v Lab exam 1 is Wed! (does not cover today’s lab) § Since many of the first were photosynthetic (i.e.

), a LOT of excess oxygen accumulated (O2 revolution)

§ Some organisms adapted to use it (aerobic respiration)

Review: Review: Phylogeny v Which are thought to have originated as v is similarity due to shared ancestry ? v Analogy is similarity due to convergent v During what event did resembling modern taxa suddenly appear en masse? v A valid is monophyletic, meaning it consists of the ancestor and all its descendants v How many mass seem to have occurred during v A paraphyletic grouping consists of an ancestral and Earth’s history? Describe one? some, but not all, of the descendants v When is adaptive likely to occur? v A polyphyletic grouping includes distantly related species but does not include their most recent common ancestor

v Maximum parsimony assumes the requiring the fewest evolutionary events is most likely

Quiz 3 (History and Phylogeny) BIOSC 041 1. How long ago is Earth thought to have formed?

2. Why might many organisms have evolved to use aerobic respiration? PROTISTS! Reference: Chapter 28 3. Which two organelles are thought to have originated as endosymbionts?

4. ______is similarity due to shared ancestry, while ______is similarity due to .

5. A valid clade is ______, meaning it consists of the ancestor taxon and all its descendants.

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Diplomonads Outline What is a ?

Euglenozoans § Everything that is not v General characteristics of protists something else v Our understanding of the relationships among protist Golden § But definitely not an animal

“SAR” clade “SAR”

groups continues to change rapidly! v The one- of v One hypothesis divides all (including protists) Apicomplexans Protista has been abandoned

into four supergroups: Forams v Protists are now recognized as Rhizarians Cercozoans § Excavata polyphyletic Radiolarians

§ “SAR” clade § Some lineages of protists Green § Archaeplastida recognized as kingdoms algae Chlorophytes Charophytes § v Protist remains the informal Unikonta Land

Amoebozoans v Roles in Ecological Communities name for highlighted taxa v “Protozoa” are animal-like Slime molds § Producers Tubulinids Entamoebas

protists Unikonta

§ Consumers Nucleariids Fungi

§ Parasites &

Animals

The Protists exhibit more structural and functional Most protists are unicellular, and small… diversity than any other group of eukaryotes v Single-celled protists can be very complex, as all biological § Include unicellular, colonial, and multicellular taxa functions are carried out by organelles in each individual § Most range in size from <1-200 µm

…but there are many exceptions… v The Protists also include colonial and multicellular taxa- particularly algae v Galatheammina (Xenophyophore) v Algae are considered protists because they don’t meet the v Benthic (deep ) protozoan, ~10 cm in diameter complex criteria of true plants v Single-celled(!!) § Range in size from 100’s um to 100’s meters (giant ) § “ruffled” surface increases surface area for gas/nutrient exchange

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Nutritional and reproductive diversity Endosymbiosis in Eukaryotic Evolution

v Protists owe their diversity to endosymbiosis- a unicellular v Nutrition engulfs another cell, which becomes an § Photoautotrophs and then an in the cell § Contain § Review:

§ Obtain from the sun and from CO2 § Mitochondria evolved by endosymbiosis of an aerobic § heterotrophic bacterium § Obtain both energy and carbon from organic , § Chloroplasts evolved by endosymbiosis of absorbed from the environment or through ingestion of photosynthetic cyanobacterium other organisms v The -bearing protists evolved into red and § (DNA of plastid in red algae and green algae closely resemble DNA of cyanobacteria) § Combine photosynthesis and v During eukaryotic evolution, red and green algae also v underwent secondary endosymbiosis, in which they were § Sexual, asexual, or both! ingested by a heterotrophic

Figure 28.2 Five Supergroups of Excavata Plastid Eukaryotes Parabasalids Euglenozoans Stramenopiles Dinoflagellates Diatoms v Our understanding of the Brown algae

“SAR” clade “SAR” Secondary Alveolates Dinoflagellates endosymbiosis relationships among protist Membranes Apicomplexans Apicomplexans are represented groups continues to change as dark lines in Ciliates Red alga the cell. rapidly Forams Cyanobacterium Rhizarians 1 2 Cercozoans 3 v One hypothesis divides all Radiolarians

Primary eukaryotes (including protists) endosymbiosis Archaeplastida Stramenopiles Red algae Green into four supergroups algae Chlorophytes

Heterotrophic Secondary Plastid Charophytes endosymbiosis eukaryote One of these Land plants

membranes was Amoebozoans lost in red and Slime molds green algal descendants. Tubulinids Secondary Entamoebas Unikonta

endosymbiosis Nucleariids

Green alga Opisthokonts Fungi

Chlorarachniophytes Choanoflagellates

Supergroup #1: Excavates Excavata: Diplomonads and Parabasalids

v These two groups lack , have modified mitochondria, v Include protists with modified mitochondria and protists and most live in anaerobic environments with unique flagella v Diplomonads v The clade Excavata is characterized by its § Have modified mitochondria called v Some members have a feeding groove § Derive energy from anaerobic biochemical pathways v This diverse group includes § Have two equal-sized nuclei and multiple flagella § Diplomonads § Are often parasites, for example, intestinalis (also known as Giardia lamblia) § Parabasalids Diplomonads Excavata § Euglenozoans Parabasalids

Euglenozoans

SAR clade Archaeplastida Unikonta

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Parabasalids Euglenozoans

v is a diverse clade that includes predatory v Have reduced mitochondria called heterotrophs, photosynthetic , and parasites that generate some energy anaerobically v Distinguishing feature v Include vaginalis, the that § A spiral or crystalline rod of unknown function inside causes a type of vaginal in females their flagella v This clade includes the § Kinetoplastids § Euglenids

Euglenozoa - Kinetoplastids More about trypanosomes

v Kinetoplastids are distinguished from other protozoa by the v Trypanosomes evade immune responses by switching surface - a single containing an organized mass of DNA (kDNA) that comprises several copies of the v A cell produces millions of copies of a single mitochondrial v The new generation produces millions of copies of a v Include free-living consumers of in freshwater, different protein marine, and moist terrestrial v These frequent changes prevent the host from developing v Also include some pathogens immunity § , which causes sleeping sickness in § Another pathogenic trypanosome causes Chagas’ disease

Euglenozoa - Euglenids Supergroup #2: SAR clade v Euglenids have one or two flagella that emerge from a v A highly diverse group of protists defined by DNA similarities pocket at one end of the cell v The “SAR” clade is a diverse monophyletic supergroup v Some species can be both autotrophic and heterotrophic named for the first letters of its three major Stramenopiles, Alveolates, and Rhizarians v This group is the most controversial of the four supergroups (sometimes split to give 5 subgroups) v Stramenopiles covered in Biosc 42

Excavata Diatoms Golden algae Stramenopiles Brown algae SAR clade SAR Dinoflagellates Apicomplexans Alveolates Ciliates Forams Cercozoans Rhizarians Radiolarians Archaeplastida Unikonta

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Alveolata Dinoflagellates

v Dinoflagellates have two flagella and each cell is reinforced v Members of the clade Alveolata have membrane-bounded sacs (alveoli) just under the plasma membrane by plates v They are abundant components of both marine and v The function of the alveoli is unknown freshwater v The alveolates include v They are a diverse group of aquatic , § Dinoflagellates mixotrophs, and heterotrophs § Apicomplexans v Toxic “red ” are caused by blooms § Ciliates

Apicomplexans More about Apicomplexans v Apicomplexans are parasites of animals, and some cause serious human diseases v Responsible for some of the most serious human disease – § No movement, no free-living forms (), (obligate parasites) v Plasmodium requires both § Complex intracellular structures and mosquitoes and humans to lifecycles (spread through host as complete its life infectious cells called sporozoites) v ~900,000 people die each § One end, the apex, contains a from malaria complex of organelles specialized to v Efforts are ongoing to develop penetrate host cells and tissues malaria vaccines § Most have sexual and asexual stages that require two or more host species for completion

Figure 28.10-3 Inside mosquito Inside human Ciliates Merozoite Sporozoites (n) Liver v Ciliates, a large varied group of protists, are named for their use of cilia to move and feed Liver cell § caudatum is a good example of a Oocyst Apex v Have large macronuclei and Merozoite Red blood 0.5 µm (n) cell small micronuclei (2n) Red blood v Genetic Variation cells § Exchange of haploid micronuclei via sexual

FERTILIZATION conjugation v Reproduction Key Gametocytes § (n) Asexual- binary Haploid (n) Diploid (2n)

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Figure 28.11 Rhizarians Contractile Oral groove

Cell mouth Cilia 50 µm v DNA evidence supports as a monophyletic clade (so it sometimes is split from SAR into its own supergroup) Food v Rhizaria includes some groups of (“testate ameobas”= with shells), including radiolarians, forams, and (a) Feeding, waste removal, and water balance cercozoans Key Conjugation v Amoebas are protists that move and feed by , Asexual MEIOSIS reproduction extensions of the cell surface v Rhizarian amoebas differ from amoebas in other clades by Haploid Diploid micronucleus Compatible micronucleus having threadlike pseudopodia mates The original Diploid macronucleus micronucleus disintegrates.

MICRONUCLEAR FUSION

(b) Conjugation and reproduction

Radiolarians Forams v called radiolarians have tests fused v Foraminiferans, or forams, are named for porous, generally into one delicate piece, usually made of silica multichambered shells, called tests v Radiolarians use their pseudopodia to engulf § Organic material hardened with CaCO3 through v Pseudopodia extend through the pores in the v Foram tests in marine sediments form an extensive v The pseudopodia of radiolarians radiate from the record central body v Many forams have endosymbiotic algae

Cercozoans Supergroup #3: Archaeplastida 20 cm v Cercozoans include most amoeboid and flagellated v Covered in detail in Biosc 42 protists with threadlike pseudopodia v Includes red algae, green algae, and land plants v They are common in marine, freshwater, and ecosystems v Most are heteroptrophs, including parasites and Excavata Dulse ( palmata) predators SAR clade

Archaeplastida 2 cm Red algae

Chlorophytes Green algae Charophytes

Land plants

Unikonta

Imbricatea (a) Ulva, sea lettuce

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Supergroup 4: Unikonts Amoebozoans v Includes animals, fungi, and some protists (that are closely v Amoebozoans are that have lobe- or tube- related to fungi and animals) shaped, rather than threadlike, pseudopodia- and no v This group includes two clades: the amoebozoans and the shell opisthokonts (animals, fungi, and related protists) v They include slime molds, tubulinids, and entamoebas v The of the eukaryotic tree remains controversial v It is unclear whether unikonts separated from other eukaryotes relatively early or late

Excavata SAR clade Archaeplastida Slime molds

Tubulinids Unikonta Entamoebas Nucleariids Fungi

Choanoflagellates Animals

Slime Molds Plasmodial Slime Molds

v Slime molds (mycetozoans) once thought to be fungi v Many species of plasmodial slime molds are brightly pigmented, usually yellow or orange v Molecular places slime molds in the clade v Two types: § Plasmodial (no cell membranes, but many nuclei) § Cellular (cell membranes present) § Give clues to evolution of multicellularity

Plasmodial Slime Molds Cellular Slime Molds v At one point in the life cycle, plasmodial slime molds form a v Cellular slime molds form multicellular aggregates in which mass called a plasmodium (not to be confused with malarial cells are separated by their membranes Plasmodium) v Cells feed individually, but can aggregate to form a fruiting v The plasmodium is not multicellular body FERTILIZATION v It is undivided by plasma membranes but contains many (n) Emerging diploid nuclei amoeba (n) Zygote SEXUAL (2n) v Extends pseudopodia through decomposing material, engulfing Solitary REPRODUCTION food by phagocytosis 600 µm amoebas (n) MEIOSIS Amoebas (n) Fruiting ASEXUAL bodies REPRODUCTION (n) Aggregated amoebas

Migrating aggregate 200 µm

Key Haploid (n) Diploid (2n)

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Tubulinids Entamoebas v Have lobe or tube-shaped pseudopodia. Typical v Entamoebas are parasites of and some “amoeboid” movement v Common unicellular amoebozoans in soil as well as v histolytica causes amebic , the freshwater and marine environments third-leading cause of human due to eukaryotic v Most are heterotrophic and actively seek and consume parasites and other protists

Opisthokonts Protists play key roles in ecological communities v Opisthokonts include animals, fungi, and several v Protists are found in diverse environments groups of protists § Aquatic, marine and terrestrial § Nucleariids (amoeba more similar to fungi) v Protists are found in all trophic levels § Choanoflagellates § Producer (photoautotrophs) § Various types of consumer (heterotrophs feeding on photoautotrophs or other heterotrophs) Excavata SAR clade § Parasites (including human pathogens) Archaeplastida § Detritovore Slime molds

Tubulinids Unikonta § Important in recycling nutrients Entamoebas Nucleariids Fungi

Choanoflagellates Animals

Photosynthetic Protists Symbiotic Protists v Many protists are important producers that obtain energy from the sun v In aquatic environments, photosynthetic protists and v Some protist symbionts prokaryotes (cyanobacteria) are the main producers benefit their hosts v In aquatic environments, photosynthetic protists are limited § Dinoflagellates by nutrients () § Primarily N and/or P, sometimes Fe photosynthesize to provide v These can explode (bloom) when limiting food for polyps that nutrients are added build reefs § -digesting protists digest cellulose in the gut of

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Parasitic Protists A Protist as Engineer?

v Plasmodium causes malaria v Galatheammina (Xenophyophore- giant ) v Can form very dense populations on undersea plains v Stirs up sediment and creates structure with slime § Creates for other bottom-dwelling organisms v shumwayae is a dinoflagellate that causes § Populations of crustaceans and worms much higher where Galatheammina is present fish kills § Plays key role in circulating C & N back into the water

v Phytophthora ramorum causes sudden oak death

Figure 28.UN06 Eukaryote Key Morphological Global warming and phytoplankton Supergroup Major Groups Characteristics Specific Examples Excavata Diplomonads and Modified mitochondria Giardia, parabasalids Trichomonas

Euglenozoans Spiral or crystalline rod in- Trypanosoma, Kinetoplastids side flagella v Phytoplankton form the basis for marine and aquatic food Euglenids webs (most phytoplankton are protists) “SAR” Clade Stramenopiles Hairy and smooth flagella Phytophthora, Diatoms v of photosynthetic protists has declined as sea surface Golden algae temperature has increased Brown algae Alveolates Membrane-enclosed sacs Pfiesteria, Dinoflagellates (alveoli) beneath plasma Plasmodium, membrane Paramecium v If continues to warm due to global Apicomplexans Ciliates warming, this could have large effects on Rhizarians Amoebas with threadlike Globigerina Radiolarians pseudopodia Forams § Marine ecosystems Cercozoans

Archaeplastida Red algae Phycoerythrin (photosyn- § Fishery yields thetic pigment) Green algae -type chloroplasts Chlamydomonas, § The global carbon cycle Ulva

Land plants (See Chapters 29 and 30.) , , , flowering plants

Unikonta Amoebozoans Amoebas with lobe- Amoeba, Slime molds shaped or tube-shaped pseudopodia Tubulinids Entamoebas Opisthokonts (Highly variable; see Choanoflagellates, Chapters 31–34.) nucleariids, animals, fungi

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