BIOLOGY Global Edition

TENTH EDITION BIOLOGY Global Edition

Campbell • Reece • Urry • Cain • Wasserman • Minorsky • Jackson 28

The Origin and Evolution of Eukaryotes

Lecture Presentation by Nicole Tunbridge and Kathleen Fitzpatrick

1 μm

a) Even a low-power microscope can reveal a great variety of organisms in a drop of pond water b)Protist is the informal name of the group of mostly unicellular eukaryotes c) Protists are eukaryotes not plants, animals or fungi.

a) Protists are eukaryotes b) Eukaryotic cells have organelles and are more complex than prokaryotic cells c) It is important to bear in mind that

a)The organisms in most eukaryotic lineages are protists, and b)Most protists are unicellular

a) Protists exhibit more structural and functional diversity than any other group of eukaryotes b) Though most protists are unicellular, there are some colonial and multicellular species c) Single-celled protists can be very complex, as all biological functions are carried out by organelles in each individual cell

a)Photoautotrophs, which contain chloroplasts b)Heterotrophs, which absorb organic molecules or ingest larger food particles c)Mixotrophs, which combine photosynthesis and heterotrophic nutrition

a) One hypothesis divides all eukaryotes (including protists) into four supergroups

Euglenozoans Stramenopiles

Diatoms Golden algae

Brown algae

“ SAR

Alveolates Dinoflagellates ” ”

Apicomplexans clade Ciliates

Forams Rhizarians Cercozoans Radiolarians

Red algae Archaeplastida Green algae Chlorophytes Charophytes

Land plants Amoebozoans

Slime molds Tubulinids

Entamoebas Unikonta

Nucleariids Opisthokonts Fungi Choanoflagellates Animals

a)The clade Excavata is characterized by its cytoskeleton b)Some members have an “excavated” feeding groove c) This group includes the diplomonads, parabasalids, and euglenozoans

Diplomonads Excavata Parabasalids

Euglenozoans

SAR clade Archaeplastida Unikonta

a) Euglenozoa is a diverse clade that includes predatory heterotrophs, photosynthetic autotrophs, mixotrophs, and parasites b) The main feature distinguishing them as a clade is a spiral or crystalline rod inside their flagella c) This clade includes the kinetoplastids and euglenids

Flagella 0.2 μm

8 μm Crystalline rod (cross section) Ring of microtubules (cross section)

a) Kinetoplastids have a single mitochondrion with an organized mass of DNA called a kinetoplast b) Free-living species are consumers of prokaryotes in freshwater, marine, and moist terrestrial ecosystems

© 2015 Pearson Education Ltd a) Some species are parasitic b) Kinetoplastids in the genus Trypanosoma cause sleeping sickness in humans, tsetse fly. c) Another pathogenic trypanosome causes Chagas’ disease, blood suckig iset leads to congestive heart desease.

9 μm

© 2015 Pearson Education Ltd a) Trypanosomes evade immune responses by switching surface proteins b) A cell produces millions of copies of a single protein (bait and switch) c) The new generation produces millions of copies of a different protein d) These frequent changes prevent the host from developing immunity

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

Long flagellum

Eyespot

Light Short flagellum detector Contractile vacuole

Nucleus Chloroplast

Plasma 5 μm membrane Euglena (LM) Pellicle

Long flagellum

Eyespot

Contractile vacuole Nucleus Chloroplast

Plasma 5 μm membrane Euglena (LM)

a)The “SAR” clade is a diverse monophyletic supergroup named for the first letters of its three major clades stramenopiles, alveolates, and rhizarians

Excavata Diatoms Golden algae Stramenopiles

Brown algae SARclade Dinoflagellates Apicomplexans Alveolates Ciliates Forams Cercozoans Rhizarians Radiolarians Archaeplastida Unikonta

a)The stramenopiles clade includes some of the most important photosynthetic organisms on Earth b)Most have a “hairy” flagellum paired with a “smooth” flagellum c) Stramenopiles include diatoms, golden algae, and brown algae

Hairy flagellum Smooth flagellum

5 μm

a)Diatoms are unicellular algae with a unique two- part, glass-like wall of silicon dioxide embedded in an organic matrix.

Figure 28.10

μ 40 40

© 2015 Pearson Education Ltd a) Diatoms are a major component of phytoplankton and are highly diverse b) Fossilized diatom walls compose much of the sediments known as diatomaceous earth c) After a diatom population has bloomed, many dead individuals fall to the ocean floor undecomposed

© 2015 Pearson Education Ltd a) This removes carbon dioxide from the atmosphere and “pumps” it to the ocean floor b) Some scientists advocate fertilizing the ocean to promote diatom blooms and the movement of carbon dioxide from the atmosphere to the ocean floor

a)Brown algae are the largest and most complex algae b)All are multicellular, and most are marine c) Brown algae include many species commonly called “seaweeds” d) brown or olive color  carotenoids

© 2015 Pearson Education Ltd a)Giant seaweeds called kelps live in deep parts of the ocean b)Brown algal seaweeds have plantlike structures: the rootlike holdfast, which anchors the alga, and a stemlike stipe, which supports the leaflike blades

Blade

Stipe

Holdfast

a)The most complex life cycles include an alternation of generations, the alternation of multicellular haploid and diploid forms b)Heteromorphic generations are structurally different, while isomorphic generations look similar

Laminaria Producing algin

10 cm

Haploid (n) Diploid (2n)

Sporangia

MEIOSIS 10 cm Sporophyte (2n) Zoospore Female Developing Gameto- sporophyte phytes Zygote (n) Mature female (2n) gametophyte Egg Male (n) FERTILIZATION

Sperm

© 2015 Pearson Education Ltd a) The diploid sporophyte produces haploid flagellated spores called zoospores b) The zoospores develop into haploid male and female gametophytes, which produce gametes c) Fertilization of gamates results in a diploid zygote, which grows into a new sporophyte

a) Members of the clade Alveolata have membrane- enclosed sacs (alveoli) just under the plasma membrane b) The alveolates include

a)Dinoflagellates b)Apicomplexans c)Ciliates

Flagellum Alveoli

Alveolate

μ 0.2

a)Apicomplexans are parasites of animals, and some cause serious human diseases b)They spread through their host as infectious cells called sporozoites c) One end, the apex, contains a complex of organelles specialized for penetrating host cells and tissues d)Most have sexual and asexual stages that require two or more different host species for completion

© 2015 Pearson Education Ltd a)The apicomplexan Plasmodium is the parasite that causes malaria b)Plasmodium requires both mosquitoes and humans to complete its life cycle c) Approximately 900,000 people die each year from malaria d)Efforts are ongoing to develop vaccines that target this pathogen

Sporozoites (n) Liver

Liver cell Apex Oocyst MEIOSIS Merozoite Red blood 0.5 μm cell (n) Red Zygote blood (2n) cells

FERTILIZATION

Gametes Game- tocytes Haploid (n) (n) Diploid (2n)

a)Ciliates, a large varied group of protists, are named for their use of cilia to move and feed b)They have large macronuclei and small micronuclei c) Genetic variation results from conjugation, in which two individuals exchange haploid micronuclei d)Conjugation is a sexual process, and is separate from reproduction, which generally occurs by binary fission

Micronucleus Food vacuoles Macronucleus

(a) Feeding, waste removal, and water balance.

Conjugation MEIOSIS Asexual reproduction

Haploid Diploid micronucleus Compatible micronucleus mates The original Diploid macronucleus micronucleus disintegrates.

MICRO- NUCLEAR FUSION

(b) Conjugation and reproduction.

Contractile vacuole Oral groove Cilia Cell mouth 50 μm

Micronucleus Food Macronucleus vacuoles

(a) Feeding, waste removal, and water balance.

a) The photosynthetic descendants of this ancient protist evolved into red algae and green algae b) Land plants are descended from the green algae c) Archaeplastida is the supergroup that includes red algae, green algae, and land plants

Excavata

SAR clade Archaeplastida Red algae Chlorophytes Green algae Charophytes Land plants Unikonta

a)Red algae are reddish in color due to an accessory pigment called phycoerythrin, which masks the green of chlorophyll b)The color varies from greenish-red in shallow water to dark red or almost black in deep water c) Red algae are usually multicellular; the largest are seaweeds d)Red algae are the most abundant large algae in coastal waters of the tropics

20 cm

8 mm ◀ Dulse (Palmaria palmata)

▼ Nori

a)Green algae are named for their grass-green chloroplasts b)Plants are descended from the green algae c) The two main groups are the charophytes and the chlorophytes d)Charophytes are most closely related to land plants

© 2015 Pearson Education Ltd a) Most chlorophytes live in fresh water, although many are marine b) Other chlorophytes live in damp soil, as symbionts in lichens, or in environments exposed to intense visible and ultraviolet radiation

− Flagella 1 μm Cell wall + 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)

Eukaryote Key Morphological Supergroup Major Groups Characteristics Specific Examples

Excavata Diplomonads and Modified mitochondria Giardia, parabasalids Trichomonas

Euglenozoans Spiral or crystalline rod in- Trypanosoma, Kinetoplastids side flagella Euglena Euglenids

“SAR” Clade Stramenopiles Hairy and smooth flagella Phytophthora, Diatoms Laminaria Golden algae Brown algae

Alveolates Membrane-enclosed sacs Pfiesteria, Dinoflagellates (alveoli) beneath plasma Plasmodium, Apicomplexans membrane Paramecium Ciliates

Rhizarians Amoebas with threadlike Globigerina Radiolarians pseudopodia Forams Cercozoans

Eukaryote Key Morphological Supergroup Major Groups Characteristics Specific Examples

Archaeplastida Red algae Phycoerythrin (photosyn- Porphyra thetic pigment)

Green algae Plant-type chloroplasts Chlamydomonas, Ulva

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

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