2/13/12 Objective: Chapter 28- Protists DISCLAIMER: You do not need to memorize the name of each protist group (see phylogenetic tree), but you will be responsible for the significance of some of the major protists discussed in class. To make it easier, I highlighted all important examples in GREEN

Overview: 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 kingdom of mostly unicellular eukaryotes Advances in eukaryotic systematics have caused the classification of protists to change significantly Protists constitute a paraphyletic group, and Protista is no longer valid as a kingdom

What’s in a junk drawer? Kingdom Protista is very diverse and where scientists place eukaryotes that are not animals, plants, or fungus.

Basic Characteristics of Protists Have eukaryotic cells (has a nucleus and organelles) Most are unicellular, algae is multicellular Very diverse kingdom

Protist Complexity Protists are unicellular, so thought to be simple, but… The protist’s one cell must carry out many processes (consume food, excrete waste, reproduce, respond to stimuli), so considered to be the most complex of eukaryotic cells

Protists are grouped by how they get nutrition 1. Animal-like protists (protozoans) are heterotrophs that ingest food 2. Fungus-like protists are heterotrophs that feed on decaying organic matter 3. Plant-like protists (algae) are autotrophs that make their own food like plants

Protists, the most nutritionally diverse of all eukaryotes, include: –Photoautotrophs, which contain chloroplasts –Heterotrophs, which absorb organic molecules or ingest larger food particles –Mixotrophs, which combine photosynthesis and heterotrophic nutrition

Endosymbiosis in Eukaryotic Evolution There is now considerable evidence that much protist diversity has its origins in endosymbiosis Mitochondria evolved by endosymbiosis of an aerobic prokaryote Plastids evolved by endosymbiosis of a photosynthetic cyanobacterium

Fig Cyanobacterium Heterotrophic eukaryote Over the course of evolution, this membrane was lost. Red alga Green alga Primary endosymbiosis Secondary endosymbiosis Secondary endosymbiosis Secondary endosymbiosis Plastid Dinoflagellates Apicomplexans Stramenopiles Plastid Euglenids Chlorarachniophytes

The plastid-bearing lineage of protists evolved into red algae and green algae On several occasions during eukaryotic evolution, red and green algae underwent secondary endosymbiosis, in which they were ingested by a heterotrophic eukaryote

Fig a Green algae Amoebozoans Opisthokonts Alveolate s Stramenopiles Diplomonads Parabasalids Euglenozoans Dinoflagellates Apicomplexan s Ciliates Diatoms Golden algae Brown algae Oomycetes Excavata Chromalveolata Rhizaria Chlorarachniophytes Forams Radiolarians Archaeplastida Red algae Chlorophytes Charophyceans Land plants Unikonta Slime molds Gymnamoebas Entamoebas Nucleariids Fungi Choanoflagellates Animals

Fig h 50 µm

Fig i 20 µm

Fig j 20 µm 50 µm

Fig l 100 µm

The clade Excavata is characterized by its cytoskeleton Some members have a feeding groove This controversial group includes the diplomonads, parabasalids, and euglenozoans Excavates include protists with modified mitochondria and protists with unique flagella

Fig. 28-UN1 Kinetoplastids Euglenids Diplomonads Parabasalids Euglenozoans Excavata Chromalveolata Rhizaria Archaeplastida Unikonta

Diplomonads and Parabasalids Diplomonads –Derive energy anaerobically, for example, by glycolysis –Have multiple flagella –Are often parasites, for example, Giardia intestinalis

Parabasalids –Have reduced mitochondria that generate some energy anaerobically –Include Trichomonas vaginalis, the pathogen that causes yeast infections in human females

Fig µm Flagella Undulating membrane

Euglenozoans Euglenozoa is a diverse clade that includes predatory heterotrophs, photosynthetic autotrophs, and pathogenic parasites The main feature distinguishing them as a clade is a spiral or crystalline rod of unknown function inside their flagella

Fig Flagella Crystalline rod Ring of microtubules 0.2 µm

Kinetoplastids Kinetoplastids have a single mitochondrion with an organized mass of DNA called a kinetoplast They include free-living consumers of prokaryotes in freshwater, marine, and moist terrestrial ecosystems This group includes Trypanosoma, which causes sleeping sickness in humans

Fig µm

Euglenids Euglenids have one or two flagella that emerge from a pocket at one end of the cell Some species can be both autotrophic and heterotrophic

Fig Long flagellum Eyespot Short flagellum Contractile vacuole Nucleus Chloroplast Plasma membrane Light detector Pellicle Euglena (LM) 5 µm

Alveolates Members of the clade Alveolata have membrane-bounded sacs (alveoli) just under the plasma membrane The function of the alveoli is unknown Alveolata includes the dinoflagellates, apicomplexans, and ciliates

Fig Flagellum Alveoli Alveolate 0.2 µm

Dinoflagellates Dinoflagellates are a diverse group of aquatic mixotrophs and heterotrophs They are abundant components of both marine and freshwater phytoplankton

Two flagella make them spin as they move through the water Dinoflagellate blooms are the cause of toxic “red tides”

Zooxanthellae -A dinoflagellate -Photosynthetic algae, mutalistic with reef- building coral -Provide oxygen to coral

Fig Flagella 3 µm

Apicomplexans Apicomplexans are parasites of animals, and some cause serious human diseases Most have sexual and asexual stages that require two or more different host species for completion

The apicomplexan Plasmodium is the parasite that causes malaria Plasmodium requires both mosquitoes and humans to complete its life cycle

Fig µm Inside human Liver Liver cell Merozoite (n) Red blood cells Gametocytes (n) Haploid (n) Diploid (2n) Key Merozoite Apex Red blood cell

Fig µm Inside human Liver Liver cell Merozoite (n) Red blood cells Gametocytes (n) Haploid (n) Diploid (2n) Key Merozoite Apex Red blood cell Zygote (2n) FERTILIZATION Gametes Inside mosquito

Fig µm Inside human Liver Liver cell Merozoite (n) Red blood cells Gametocytes (n) Haploid (n) Diploid (2n) Key Merozoite Apex Red blood cell Zygote (2n) FERTILIZATION Gametes Inside mosquito MEIOSIS Oocyst Sporozoites (n)

Ciliates Ciliates, a large varied group of protists, are named for their use of cilia to move and feed They have large macronuclei and small micronuclei The micronuclei function during conjugation, a sexual process that produces genetic variation

Fig Contractile vacuole Oral groove Cell mouth Cilia Micronucleus Macronucleus Food vacuoles (a) Feeding, waste removal, and water balance 50 µm MEIOSIS Compatible mates Diploid micronucleus Haploid micronucleus The original macronucleus disintegrates. Diploid micronucleus MICRONUCLEAR FUSION (b) Conjugation and reproduction Key Conjugation Reproduction

Stramenopiles The clade Stramenopila includes several groups of heterotrophs as well as certain groups of algae Most have a “hairy” flagellum paired with a “smooth” flagellum

Fig Smooth flagellum Hairy flagellum 5 µm

Ex : Diatoms Diatoms are unicellular algae with a unique glass-like wall made of silica

Diatoms are a major component of phytoplankton and are highly diverse Fossilized diatom walls compose much of the sediments known as diatomaceous earth

Golden Algae Golden algae are named for their color, which results from their yellow and brown carotenoids All golden algae are photosynthetic, and some are also heterotrophic Most are unicellular, but some are colonial

Fig µm Outer container Flagellum Living cell

Brown Algae Brown algae are the largest and most complex algae All are multicellular, and most are marine Brown algae include many species commonly called “seaweeds”

Ex: Giant Kelp (Brown Algae) VERY important habitat for many marine species Area of fish spawning Keystone species (beaver) why?

Giant seaweeds called kelps live in deep parts of the ocean The algal body is plantlike but lacks true roots, stems, and leaves and is called a thallus The rootlike holdfast anchors the stemlike stipe, which in turn supports the leaflike blades

Fig Blade Stipe Holdfast

Alternation of Generations A variety of life cycles have evolved among the multicellular algae The most complex life cycles include an alternation of generations, the alternation of multicellular haploid and diploid forms

Fig cm Haploid (n) Diploid (2n) Key Sporangia Sporophyte (2n) Zoospore MEIOSIS Female Gametophytes (n) Egg Male Sperm

Fig cm Haploid (n) Diploid (2n) Key Sporangia Sporophyte (2n) Zoospore MEIOSIS Female Gametophytes (n) Egg Male Sperm FERTILIZATION Zygote (2n) Developing sporophyte Mature female gemetophyte (n)

Oomycetes (Water Molds and Their Relatives) Oomycetes include water molds, white rusts, and downy mildews They were once considered fungi based on morphological studies Most oomycetes are decomposers or parasites They have filaments (hyphae) that facilitate nutrient uptake Their ecological impact can be great, as in Phytophthora infestans causing potato blight

Fig Germ tube Cyst Hyphae ASEXUAL REPRODUCTION Zoospore (2n) Zoosporangium (2n) Haploid (n) Diploid (2n) Key Oogonium Egg nucleus (n) Antheridial hypha with sperm nuclei (n) MEIOSIS Zygote germination SEXUAL REPRODUCTION Zygotes (oospores) (2n) FERTILIZATION

Red algae and green algae are the closest relatives of land plants Over a billion years ago, a heterotrophic protist acquired a cyanobacterial endosymbiont The photosynthetic descendants of this ancient protist evolved into red algae and green algae Land plants are descended from the green algae Archaeplastida is a supergroup used by some scientists and includes red algae, green algae, and land plants

Red Algae Red algae are reddish in color due to an accessory pigment, which masks the green of chlorophyll Pigment reflects red light and absorbs blue ( blue light can penetrate deeper depths, so red algae can grow in deeper areas of ocean) Red algae are the most abundant large algae in coastal waters of the tropics

Fig Bonnemaisonia hamifera 20 cm 8 mm Dulse (Palmaria palmata) Nori. The red alga Porphyra is the source of a traditional Japanese food. The seaweed is grown on nets in shallow coastal waters. The harvested seaweed is spread on bamboo screens to dry. Paper-thin, glossy sheets of nori make a mineral-rich wrap for rice, seafood, and vegetables in sushi.

Green Algae Green algae are named for their grass-green chloroplasts Plants are descended from the green algae

Fig a (a) Ulva, or sea lettuce 2 cm

Rhizarians are a diverse group of protists defined by DNA similarities Ex: Amoebas move and feed by pseudopodia

Pseudopod Pseudopod: Move by extending lobes of cytoplasm, also used to take in food Pseudopod = “false foot” Ex: Amoeba

Forams

Slime Molds Slime molds, or mycetozoans, were once thought to be fungi

Plasmodial Slime Molds When feeding, form a mass of cytoplasm called “plasmodium” Creeps along ground, rocks, or logs eating bacteria or other small organisms v=GScyw3ammmk

Cellular Slime Molds Cellular slime molds form multicellular aggregates in which cells are separated by their membranes Cells feed individually, but can aggregate to form a fruiting body

Fig. 28-UN6