1. General Features of Protists

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1 Chapter 28: Protists 1. General Features of Protists 2. Survey of the Protista A. The Excavata B. The SAR Clade C. The Archaeplastida D. The Unikonta 1. General Features of Protists All Protists are Eukaryotes Eukaryotic organisms consist of 1 or more eukaryotic cells: Prokaryotic cell eukaryotic cells contain a true nucleus and other membranebound organelles Nucleus Eukaryotic cell Organelles Most eukaryotes are single-celled organisms, most of which are protists (i.e., not fungi, plants or animals). 1

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 algae

Plasma membrane DNA Ancestral prokaryote Cytoplasm The endosymbiont theory proposes that mitochondria & chloroplasts are derived from internalized prokaryotes.

2 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 algae ) some are chemoheterotrophs (commonly called protozoa ) some have characteristics of both (mixotrophs) protists can reproduce sexually, asexually, or both Endosymbiosis in Eukaryotic Evolution Plasma membrane DNA Ancestral prokaryote Cytoplasm The endosymbiont theory proposes that mitochondria & chloroplasts are derived from internalized prokaryotes. Nucleus Endoplasmic reticulum Photosynthetic prokaryote Nuclear envelope Mitochondrion Aerobic heterotrophic prokaryote Mitochondrion Plastid Ancestral heterotrophic eukaryote Ancestral photosynthetic eukaryote A Closer Look at Plastid Evolution Membranes are represented as dark lines in the cell. Secondary endosymbiosis Dinoflagellates Cyanobacterium Red alga Plastid Primary endosymbiosis Stramenopiles Nucleus Heterotrophic eukaryote One of these membranes was lost in red and green algal descendants. Secondary endosymbiosis Secondary endosymbiosis Plastid Euglenids Green alga Chlorarachniophytes 2

Protists No Longer Constitute a Single Kingdom The traditional grouping of eukaryotes involved 4 kingdoms: PROTISTA FUNGI PLANTAE ANIMALIA However this is not consistent with phylogenies based on

2 Diplomonads Parabasalids Euglenozoans Excavata Excavata 5 μm 4 Supergroups Stramenopiles Alveolates Rhizarians Amoebozoans Opisthokonts Green algae Diatoms Golden algae Brown algae Dinoflagellates

3 Protists No Longer Constitute a Single Kingdom 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 Diplomonads Parabasalids Euglenozoans Excavata Excavata 5 μm 4 Supergroups Stramenopiles Alveolates Rhizarians Amoebozoans Opisthokonts Green algae Diatoms Golden algae Brown algae Dinoflagellates Apicomplexans Ciliates Forams Cercozoans Radiolarians Red algae Chlorophytes Charophytes Land plants Slime molds Tubulinids Entamoebas Nucleariids Fungi Choanoflagellates Animals SAR clade Archaeplastida Unikonta Giardia intestinalis, Archaeplastida SAR Clade Diatom diversity 50 μm Volvox, a colonial freshwater green alga Unikonta 100 μm 50 μm 1. Excavata 2. SAR Clade The evolutionary history of all eukaryotes currently consists of 4 supergroups: 3. Archaeplastida includes all land plants 4. Unikonta includes fungi & animals All eukaryotes that are not plants, animals or fungi are considered to be Protists. A unikont amoeba 2A. Survey of the Protista The Excavata Diplomonads Parabasalids Euglenozoans Excavata SAR clade Archaeplastida Unikonta 3

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

mitosomes and derive energy by anaerobic processes. They also have 2 nuclei and multiple flagella.

4 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 have reduced mitochondria called mitosomes and derive energy by anaerobic processes. They also have 2 nuclei and multiple flagella. Diplomonads Many are parasites such as Giardia intestinalis shown here: Flagella Parabasalids Parabasalids have reduced mitochondria called hydrogenosomes and thrive in anaerobic environments. Trichomonas vaginalis, a sexually transmitted human pathogen shown below is one example Undulating membrane 5 μm 4

Euglenozoans The Euglenozoa is a diverse clade that includes predatory heterotrophs, photosynthetic autotrophs, mixotrophs, and parasites. Flagella 0.

(cross section) Ring of microtubules (cross section) KINETOPLASTIDS EUGLENIDS Kinetoplastids Kinetoplastids have a single mitochondrion containing an

includes the genus Trypanosoma which contains parasites that cause sleeping sickness and Chaga s disease RBC 9 μm Euglenids Euglenids have 1 or 2

5 Euglenozoans The Euglenozoa is a diverse clade that includes predatory heterotrophs, photosynthetic autotrophs, mixotrophs, and parasites. Flagella 0.2 μm a characteristic feature of this clade is the crystalline rod structure within their flagella members of this clade include: 8 μm Crystalline rod (cross section) Ring of microtubules (cross section) KINETOPLASTIDS EUGLENIDS Kinetoplastids Kinetoplastids have a single mitochondrion containing an unusual organized mass of DNA called a kinetoplast. includes the genus Trypanosoma 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 Euglena, are both autotrophic and heterotrophic (i.e., mixotrophs). Long flagellum Eyespot Short flagellum Contractile vacuole Light detector Nucleus Chloroplast Euglena (LM) 5 μm Plasma membrane Pellicle 5

2B. Survey of the Protista The SAR Clade Diatoms Golden algae Brown algae Dinoflagellates Apicomplexans Ciliates Forams Cercozoans Radiolarians Stramenopiles

based on DNA similarities that includes the following: STRAMENOPILES ALVEOLATES RHIZARIANS 5 μm Stramenopiles Most members of the Stramenopile clade have both hairy

6 2B. Survey of the Protista The SAR Clade Diatoms Golden algae Brown algae Dinoflagellates Apicomplexans Ciliates Forams Cercozoans Radiolarians Stramenopiles Alveolates Rhizarians Excavata SAR clade 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 5 μm Stramenopiles Most members of the Stramenopile clade have both hairy and smooth flagella. this clade includes the following ecologically important groups of photosynthetic organisms: Smooth flagellum Hairy flagellum DIATOMS GOLDEN ALGAE BROWN ALGAE 6

40 μm 2/19/2015 Diatoms Diatoms have unique glass-like walls made of silicon dioxide and

their remains are the main components of white sediments referred to as diatomaceous

, the white cliffs of Dover ) Flagellum Outer container Living cell Golden Algae contain

two flagella 25 μm most are singlecelled though some are colonial Brown Algae Brown

7 40 μm 2/19/2015 Diatoms Diatoms have unique glass-like walls made of silicon dioxide and are a significant portion of phytoplankton in the oceans. their remains are the main components of white sediments referred to as diatomaceous earth (e.g., the white cliffs of Dover ) Flagellum Outer container Living cell Golden Algae contain yellow and brown carotenoids which give them their characteristic color typically have two flagella 25 μm most are singlecelled though some are colonial Brown Algae Brown algae are all multicellular and are the largest algae. includes many seaweeds such as kelp Blade although brown algae are not plants, many have plant-like structures shown in this image Stipe Holdfast 7

0.2 μm 2/19/2015 Sporangia Haploid Diploid (2n) Alternation of Generations 10 cm Mature female gametophyte Developing sporophyte Zygote (2n) FERTILIZATION

Alternation of Generations the alternation between multicellular haploid and diploid forms Flagellum Alveoli Alveolates Members of the Alveolate clade have

this clade includes the following: DINOFLAGELLATES Alveolate APICOMPLEXANS CILIATES Dinoflagellates Dinoflagellates are also an important component of

8 0.2 μm 2/19/2015 Sporangia Haploid Diploid (2n) Alternation of Generations 10 cm Mature female gametophyte Developing sporophyte Zygote (2n) FERTILIZATION Sporophyte (2n) Female Egg MEIOSIS Gametophytes Sperm Zoospore Male many multicellular algae have a life cycle similar to that of plants called the Alternation of Generations the alternation between multicellular haploid and diploid forms Flagellum Alveoli Alveolates Members of the Alveolate clade have membrane enclosed sacs called alveoli must beneath the plasma membrane. this clade includes the following: DINOFLAGELLATES Alveolate APICOMPLEXANS CILIATES Dinoflagellates Dinoflagellates are also an important component of phytoplankton and have 2 flagella, one of which wraps around the cell and causes it to rotate. 3 μm Flagella (a) Dinoflagellate flagella are responsible for the algal blooms known as red tides (b) Red tide in the Gulf of Carpentaria in northern Australia 8

Apicomplexans The Apicomplexans are parasites of animals that have complex life cycles with multiple hosts.

Liver Merozoite Plasmodium Life Cycle MEIOSIS Zygote (2n) FERTILIZATION Oocyst Merozoite Gametes Red blood cells Liver cell Gametocytes Red blood cell Haploid Diploid

5 μm mosquitoes are the definitive host (in which sexual reproduction occurs) humans are the intermediate host (in which reproduction is asexual) 50 μm Contractile

9 Apicomplexans The Apicomplexans are parasites of animals that have complex life cycles with multiple hosts. the most significant genus in this clade is Plasmodium, the cause of malaria nearly 1 million people each year die from malaria Inside mosquito Sporozoites Inside human Liver Merozoite Plasmodium Life Cycle MEIOSIS Zygote (2n) FERTILIZATION Oocyst Merozoite Gametes Red blood cells Liver cell Gametocytes Red blood cell Haploid Diploid (2n) Apex 0.5 μm mosquitoes are the definitive host (in which sexual reproduction occurs) humans are the intermediate host (in which reproduction is asexual) 50 μm Contractile vacuole Cilia Ciliates The Ciliates clade is a large group characterized by cilia used for locomotion and/or feeding and 2 nuclei, one macronucleus and one micronucleus. the genus Paramecium is a good example Oral groove Cell mouth Ciliates also engage in a form of sexual reproduction called conjugation Micronucleus Macronucleus Food vacuoles (a) Feeding, waste removal, and water balance. 9

Conjugation in Ciliates Compatible mates MEIOSIS Conjugation Asexual reproduction Diploid

Haploid micronucleus Diploid micronucleus MICRO- NUCLEAR FUSION (b) Conjugation and reproduction.

10 Conjugation in Ciliates Compatible mates MEIOSIS Conjugation Asexual reproduction Diploid micronucleus The original macronucleus disintegrates. Haploid micronucleus Diploid micronucleus MICRO- NUCLEAR FUSION (b) Conjugation and reproduction. Rhizarians The Rhizarians are mostly amoebas containing pseudopodia that are threadlike (unlike the Amoebozoa in the Unikonta clade. this clade includes the following: RADIOLARIANS FORAMS CERCOZOANS Radiolarians have delicate, symmetrical endoskeletons made typically of silica. Radiolarians the pseudopodia extend from the cell to catch prey Pseudopodia 200 μm 10

Forams Foraminiferans ( hole bearers ), or forams for short, are singlecelled heterotrophs that

foram tests are found throughout the fossil record and their tests can be analyzed to estimate ocean

Paulinella chromatophora are autotrophs that contain unique photosynthetic structures called

11 Forams Foraminiferans ( hole bearers ), or forams for short, are singlecelled 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 ocean temperatures in ancient times Cercozoans Chromatophore most are heterotrophs, though a few such as Paulinella chromatophora are autotrophs that contain unique photosynthetic structures called chromatophores 5 μm 2C. Survey of the Protista The Archaeplastida Excavata SAR clade Chlorophytes Charophytes Red algae Green algae Land plants Archaeplastida Unikonta 11

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

pigment called phycoerythrin. phycoerythrin absorbs non-red light many red algae live in deep water where red light does not penetrate This group includes many seaweeds some of which are edible.

12 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 Nori 8 mm Dulse (Palmaria palmata) The red algae contain, in addition to chlorophyll, a red accessory pigment called phycoerythrin. phycoerythrin absorbs non-red light many red algae live in deep water where red light does not penetrate This group includes many seaweeds some of which are edible. Green Algae Green algae contain green chloroplasts (due to chlorophyll) and includes 2 main groups: CHLOROPHYTES most live in fresh water CHAROPHYTES closest relatives to plants 2 cm (b) Caulerpa, an intertidal chlorophyte (a) Ulva, or sea lettuce 12

Opisthokonts Amoebozoa 2/19/2015 Chlorophyte Life Cycle Most chlorophytes have complex life cycles with both sexual and asexual reproductive stages: Flagella 1 μm Cell wall Nucleus +

Survey of the Protista The Unikonta Slime molds Tubulinids Entamoebas Nucleariids Fungi Choanoflagellates Animals Excavata SAR clade Archaeplastida Unikonta The Unikonta This group

13 Opisthokonts Amoebozoa 2/19/2015 Chlorophyte Life Cycle Most chlorophytes have complex life cycles with both sexual and asexual reproductive stages: Flagella 1 μm Cell wall Nucleus + Gamete + Cross section of cupshaped chloroplast (TEM) Zoospore ASEXUAL REPRODUCTION Mature cell FERTILIZATION SEXUAL REPRODUCTION Zygote (2n) + Haploid + MEIOSIS Diploid (2n) 2D. Survey of the Protista The Unikonta Slime molds Tubulinids Entamoebas Nucleariids Fungi Choanoflagellates Animals Excavata SAR clade Archaeplastida Unikonta The Unikonta This group contains 2 major clades: AMOEBOZOA all of which are protists: SLIME MOLDS TUBULINIDS ENTAMOEBAS OPISTHOKONTS includes animals and fungi in addition to some protists: NUCLEARIIDS CHOANOFLAGELLATES 13

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

separation of nuclei by membranes (i.e., a plasmodium), thus they are not considered to be multicellular.

cells feed individually and can aggregate to migrate and form a fruiting body species such as Dyctiostelium discoideum are studied to better

14 Amoebozoans Amoebozoans have tube or lobe-shaped pseudopodia (unlike the Rhizaria). Amoeba proteus, a tubulinid Entamoeba 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 Mold Life Cycle 600 μm Fruiting bodies Spores Emerging amoeba Solitary amoebas (feeding stage) ASEXUAL REPRODUCTION Aggregated amoebas Migrating aggregate FERTILIZATION SEXUAL REPRO- DUCTION 200 μm Zygote (2n) MEIOSIS Amoebas Haploid Diploid (2n) 14

15 Zygote (2n) FERTILIZATION Feeding plasmodium Mature plasmodium (preparing to fruit) 4 cm Flagellated cells Young Amoeboid sporangium cells Mature sporangium Germinating spore Spores MEIOSIS Plasmodial Slime Mold Life Cycle Haploid Diploid (2n) Stalk 15

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2014 Pearson Education, Inc. 1 1 4.5 bya 3.5 2.5 1.5 500 mya 1.8 bya 1.5 bya 1.3 bya 1.2 bya 750 mya 635 mya 600 mya 0.5 cm 550 mya 535 mya 1 cm 20 µm (a) A 1.8-billionyear-old fossil eukaryote (b) Tappania, a 1.5-billion-year-old fossil