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Home , Amoeba, Amoeba (genus), Dinoflagellate, Protozoa

Chapter 28:

1. General Features of Protists 2. Survey of the Protista A. The B. The SAR C. The D. The Unikonta 1. General Features of Protists All Protists are Eukaryotic consist of 1 or more eukaryotic cells: Prokaryotic • eukaryotic cells contain a “true nucleus” and other membrane- bound

Nucleus Most eukaryotes are single-celled organisms, most of which are protists (i.e., not fungi, or ).

Eukaryotic cell Organelles Protists have Diverse Characteristics

Protists are much more diverse that plants, animals & fungi:

• most are unicellular, though some are multicellular

• some are photoautotrophs (commonly called “”)

• some are chemoheterotrophs (commonly called “”)

• some have characteristics of both ()

• protists can reproduce sexually, asexually, or both Endosymbiosis in Eukaryotic Evolution Plasma membrane The theory proposes that mitochondria & are DNA derived from internalized . Ancestral Nucleus Endoplasmic Photosynthetic reticulum prokaryote

Mitochondrion Nuclear envelope

Aerobic heterotrophic prokaryote

Mitochondrion

Ancestral Ancestral photosynthetic heterotrophic eukaryote A Closer Look at Plastid Evolution

Dinoflagellates Membranes Secondary are represented endosymbiosis as dark lines in the cell. Red alga Cyanobacterium Plastid

1 2 3 Primary endosymbiosis

Nucleus Secondary Plastid Heterotrophic endosymbiosis eukaryote One of these membranes was lost in red and green algal descendants. Secondary endosymbiosis Green alga

Chlorarachniophytes Protists No Longer Constitute a Single

The traditional grouping of eukaryotes involved 4 kingdoms: PROTISTA FUNGI PLANTAE ANIMALIA

However this is not consistent with phylogenies based on recent molecular analysis which supports the following 4 supergroups… Figure 28.2 ■ Excavata 5 μm Excavata 4 Supergroups

Euglenozoans Stramenopiles ■ “SAR” Clade 50 μm The evolutionary

Brown algae intestinalis, history of all “SAR” clade “SAR”

Alveolates eukaryotes Apicomplexans currently consists Forams

Rhizarians of 4 supergroups: Cercozoans diversity ■ Archaeplastida Radiolarians 50 μm 1. Excavata

Red algae Archaeplastida Chlorophytes 2. SAR Clade Charophytes 3. Archaeplastida Land plants Amoebozoans • includes all land plants

Slime molds , a colonial freshwater green alga Tubulinids ■ Unikonta 4. Unikonta Entamoebas Unikonta • includes fungi & animals

Nucleariids Fungi All eukaryotes that are not plants, animals or fungi are Animals 100 μm considered to be Protists. A unikont 2A. Survey of the Protista The Excavata

Diplomonads Excavata

Parabasalids

Euglenozoans

SAR clade Archaeplastida Unikonta General Characteristics of Excavates

Below are some of the characteristics seen in Excavates:

• some members have an “excavated” feeding grooves that are associated with unique cytoskeletal structures • many have modified “unclassical” mitochondria • most have 2 or more flagella

• includes the following major groups:

DIPOMONADS PARABASALIDS EUGLENOZOANS Diplomonads

Diplomonads have reduced mitochondria called and derive energy by anaerobic processes. They also have 2 nuclei and multiple flagella.

Many are parasites such as Giardia intestinalis shown here: Parabasalids Parabasalids have reduced mitochondria called and thrive in anaerobic environments. • vaginalis, a sexually transmitted human shown below is one example

Flagella

Undulating membrane 5 μm Euglenozoans The is a diverse clade that includes predatory , photosynthetic , mixotrophs, and parasites.

Flagella • a characteristic feature of this 0.2 μm clade is the crystalline rod structure within their flagella

• members of this clade include:

KINETOPLASTIDS 8 μm Crystalline rod (cross section) EUGLENIDS Ring of (cross section) Kinetoplastids Kinetoplastids have a single mitochondrion containing an unusual organized mass of DNA called a .

• includes the which contains parasites that cause “sleeping sickness” and Chaga’s disease

RBC 9 μm Euglenids Euglenids have 1 or 2 flagella, and some members of this clade, such as the genus , are both autotrophic and heterotrophic

(i.e., mixotrophs). Long

Eyespot

Light Short flagellum detector Contractile

Nucleus

Plasma 5 μm membrane Euglena (LM) Pellicle 2B. Survey of the Protista The SAR Clade

Excavata Diatoms

Golden algae Stramenopiles SAR SAR clade Dinoflagellates Apicomplexans Ciliates Forams Cercozoans Rhizarians Radiolarians Archaeplastida Unikonta General Characteristics of the SAR Clade

The SAR clade is a highly diverse monophyletic supergroup based on DNA similarities that includes the following:

STRAMENOPILES

ALVEOLATES

RHIZARIANS Stramenopiles

Most members of the clade have both “hairy” and smooth flagella. • this clade includes the following ecologically important groups of photosynthetic

Hairy organisms: flagellum Smooth DIATOMS flagellum GOLDEN ALGAE BROWN ALGAE 5 μm and are a significantportion of Diatoms haveglass unique

40 μm • Diatoms of Dover”) “diatomaceous“whitethe cliffs (e.g., earth” whitesediments referred to as remainsmain componentstheir arethe of - like walls made ofsilicondioxide in the . in the Flagellum Golden Algae

Outer container • contain yellow and brown carotenoids Living cell which give them their characteristic color

• typically have two flagella

• most are single- celled though some are colonial 25 μm Brown Algae

Brown algae are all multicellular and are the largest algae.

• includes many “” Blade such as kelp

• although brown algae are Stipe not plants, many have -like structures shown in this image Holdfast Haploid (n) Alternation of Diploid (2n)

Sporangia Generations

• many multicellular 10 cm algae have a cycle Sporophyte similar to that of (2n) Zoospore Female plants called the Developing Gameto- “Alternation of sporophyte phytes Generations” – the (n) Mature female (2n) gametophyte Egg Male alternation between (n) FERTILIZATION multicellular haploid and diploid forms Alveolates Members of the clade have membrane enclosed sacs called alveoli must beneath the plasma membrane.

Flagellum Alveoli • this clade includes the following:

DINOFLAGELLATES

Alveolate

APICOMPLEXANS m

μ CILIATES 0.2 0.2 Dinoflagellates Flagella

Dinoflagellates are also an (a) important component of flagella phytoplankton and have 2 flagella, one of which wraps around the cell and causes it to 3 μm rotate.

• are responsible for the algal blooms known as “red tides” (b) in the Gulf of Carpentaria in northern Australia Apicomplexans The Apicomplexans are parasites of animals that have complex life cycles with multiple hosts.

• the most significant genus in this clade is , the cause of

• nearly 1 million people each die from malaria Inside mosquito Inside human Merozoite Plasmodium Sporozoites (n) Liver Life Cycle

Liver cell • mosquitoes are Apex the definitive Oocyst MEIOSIS (in which sexual Merozoite Red blood 0.5 μm cell (n) Red Zygote blood occurs) (2n) cells • humans are the

FERTILIZATION intermediate host (in which reproduction Gametes Game- is asexual) tocytes Haploid (n) (n) Diploid (2n) Ciliates The Ciliates clade is a large group characterized by cilia used for locomotion and/or feeding and 2 nuclei, one and one . • the genus is a good example

Contractile • Ciliates also engage vacuole in a form of sexual Oral groove Cilia Cell mouth reproduction called 50 μm conjugation…

Micronucleus Food Macronucleus

(a) Feeding, waste removal, and water balance. Conjugation in Ciliates

Compatible mates Conjugation Asexual MEIOSIS reproduction

Haploid Diploid micronucleus micronucleus The original macro- Diploid nucleus disintegrates. micronucleus

MICRO- NUCLEAR FUSION

(b) Conjugation and reproduction. Rhizarians The Rhizarians are mostly containing that are threadlike (unlike the in the Unikonta clade.

• this clade includes the following:

RADIOLARIANS

FORAMS

CERCOZOANS Radiolarians Radiolarians have delicate, symmetrical endoskeletons made typically of silica.

• the pseudopodia extend from the cell to catch prey Pseudopodia

200 μm Forams Foraminiferans (“hole bearers”), or forams for short, are single- celled heterotrophs that characteristically have multi-chambered shells called tests.

• foram tests are found throughout the fossil record and their tests can be analyzed to estimate temperatures in ancient times Cercozoans

Chromatophore

• most are heterotrophs, though a few such as chromatophora are autotrophs that contain unique photosynthetic structures called chromatophores

5 μm 2C. Survey of the Protista The Archaeplastida

Excavata

SAR clade Archaeplastida

Chlorophytes Green algae Charophytes

Land plants

Unikonta The Archaeplastida

The supergroup Archaeplastida contains the following:

RED ALGAE GREEN ALGAE LAND PLANTS

• molecular and other data indicate the land plants are descendants of the green algae, though only the red and green algae are considered to be protists ► Bonnemaisonia hamifera Red Algae

20 cm The red algae contain, in addition to , a red accessory pigment called phycoerythrin.

• phycoerythrin absorbs non-red light 8 mm ◀ Dulse (Palmaria palmata) • many red algae live in deep water

▼ Nori where red light does not penetrate

This group includes many seaweeds some of which are edible. Green Algae

Green algae contain 2 cm (a) Ulva, or lettuce green chloroplasts (due to chlorophyll) and includes 2 main groups:

CHLOROPHYTES • most live in fresh water (b) Caulerpa, an intertidal CHAROPHYTES chlorophyte • closest relatives to plants Chlorophyte Life Cycle Most chlorophytes have complex life cycles with both sexual and asexual reproductive stages:

− Flagella 1 μm + Gamete − (n) + Nucleus

Zoospore Mature cell (n) FERTILIZATION Cross ASEXUAL SEXUAL section REPRODUCTION REPRODUCTION of cup- Zygote shaped (TEM) (2n) chloroplast − +

+ − MEIOSIS Haploid (n) Diploid (2n) 2D. Survey of the Protista The Unikonta

Excavata SAR clade Archaeplastida

Slime molds

Tubulinids Unikonta

Entamoebas Amoebozoa Nucleariids Fungi Choanoflagellates

Opisthokonts Animals The Unikonta

This group contains 2 major :

AMOEBOZOA • all of which are protists: SLIME MOLDS TUBULINIDS ENTAMOEBAS

OPISTHOKONTS • includes animals and fungi in addition to some protists: NUCLEARIIDS CHOANOFLAGELLATES Amoebozoans

Amoebozoans have tube or lobe-shaped pseudopodia (unlike the ).

Amoeba proteus, a tubulinid histolytica Slime Molds

Plasmodial slime molds form multicellular aggregates in which there is no separation of nuclei by membranes (i.e., a plasmodium), thus they are not considered to be multicellular.

Cellular slime molds form multicellular aggregates in which cells are separated by their membranes. • cells feed individually and can aggregate to migrate and form a fruiting body • species such as Dyctiostelium discoideum are studied to better understand the origins of multicellularity Cellular Slime (n) FERTILIZATION Emerging Mold Life Cycle amoeba (n) SEXUAL Zygote REPRO- (2n) Solitary amoebas DUCTION 600 μm (feeding stage) MEIOSIS (n) ASEXUAL REPRODUCTION Amoebas Aggregated (n) amoebas

Fruiting Migrating aggregate bodies 200 μm (n)

Haploid (n) Diploid (2n) Zygote (2n)

Feeding FERTILIZATION plasmodium

Mature plasmodium (preparing to fruit) 4 cm Young Flagellated Amoeboid sporangium cells cells (n) (n) Mature Plasmodial sporangium Germinating Spores (n) Life Cycle MEIOSIS Stalk Haploid (n) Diploid (2n)