Protista

Eukaryotic Kingdoms• Animalia

– multicellular, motile, ingestive heterotrophs

• Fungi

– multicellular, filamentous, absorptive heterotrophs

• Plantae

– multicellular, embryophytic, photoautotrophs

Eukaryotic Kingdoms• Protista

– non-animal, non-fungal, non-plant eukaryotes

– mostly unicellular

– several distinct lineages

– modern representatives of earliest eukaryotic lineage(s)

non-plantFigure 28-1

non-animal

Eukaryotic Origins

• The modern eukaryotic cell type probably arose in stages– a proto-eukaryote arose from a prokaryotic

ancestor– the rigid cell surface was replaced with a

flexible cell surface• increased surface area for exchange of materials with environment

• pseudo-internal membranes for localized metabolism

early “internal”

membranesFigure 28-2

Eukaryotic Origins

• The modern eukaryotic cell probably arose in stages.– the rigid cell surface was replaced with a

flexible cell surface• internalized cell membranes formed the nuclear envelope

• digestive endocytosis increased the capacity for resource uptake

Eukaryotic Origins

• The modern eukaryotic cell probably arose in stages.– the rigid cell surface was replaced with a

flexible cell surface– origin of a cytoskeleton

• required proteins not encoded in modern Bacteria or Archaea genomes

• produced the diversity of morphology and motility in unicellular eukaryotic cell types

Eukaryotic Origins• The modern eukaryotic cell probably arose in

stages.

– the origin of organelles by endosymbiosis

• peroxisomes detoxify products of oxygen metabolism

• mitochondria provide heterotrophic energy generation using oxygen

–a few eukaryotes lack mitochondria

two eukaryotes

that lack

mitochondriaFigure 28-10

Eukaryotic Origins• The modern eukaryotic cell probably arose in

stages.

– origin of organelles by endosymbiosis

• chloroplasts provide an autotrophic energy/carbon source and generate oxygen

Figure 28-3

Modern Eukaryotes

• General characters of modern protists– inhabit aquatic or damp sites– exhibit diverse structures– utilize multiple nutritional modes (but fewer

than prokaryotes)• “protozoans” (a polyphyletic group)

–ingestive heterotrophs• “algae” (a polyphyletic group)

–photoautotrophs

Amoeba proteusFigure 28-4

Modern Eukaryotes• General characters of modern protists

– locomotion• none• amoeboid

–pseudopods structured by cytoskeletons• ciliary

–provides fast & precise movement

ciliate diversityFigure 28-15

Modern Eukaryotes• General characters of modern protists

– locomotion• none• amoeboid

–pseudopods structured by cytoskeletons• ciliary

–provides fast & precise movement• flagellar

–whiplike movement pushes/pulls cells

twoflagellated

protistsFigure 28-11

food vacuole

in ParameciumFigure 28-6

Modern Eukaryotes

• General characters of modern protists

– various vesicles

• food vacuole

• contractile vacuole

contractile vacuoles expel excess waterFigure 28-5

calcareous shells of foraminiferaFigure 28-7

Modern Eukaryotes

• General characters of modern protists

– diverse cell surfaces

• plasma membrane only

• plant-like cell wall

• calcium carbonate-reinforced shell

• aggregated sand particles

• proteinaceous pellicle

• glassy silicate shells

transparent glassy shells on

radiolariansfigure 28.8

Endosymbiosis• mitochondria and chloroplasts are descended

from endosymbiotic proteobacteria and cyanobacteria– 2-membrane envelopes– incomplete, but functional, genomes– incapable of extracellular existence

protists in a protistFigure 28-8

Endosymbiosis

• modern radiolarians– contain endosymbiont protists that are

potentially free-living organisms• haptophytes, euglenoids, stramenopiles

– have chloroplasts with 3 membranes• dinoflagellates & cryptomonads

– have chloroplasts with 4 membranes

Figure 28-29

Modern Protists

• Life Cycles– asexual or sexual reproduction– asexual reproduction with genetic

recombination• Asexual reproduction

– binary fission– multiple fission– budding– sporulation

Modern Protists

• Life Cycles– sexual reproduction

• gametogenic meiosis [animal-like]• sporogenic meiosis [plant-like]

Protist Phylogenies

• The protists are not a monophyletic group

– several monophyletic groups are being defined among the protists

• rRNA sequencing

• the significance of morphological, metabolic, life cycle characters is being evaluated

aphylogeny of protist groupsFigure 28-9

Diplomonads & Parabasalids• oldest known clade(s) of protists• lack mitochondria (secondary reduction?)• some cause human diseases

– Giardia lamblia - a diplomonad

– Trichomonas - a parabasilid

Protist Phylogenies

• The Euglenozoa

– unicellular, asexual flagellates

– Euglenoids

• complex cellular organization

• two unequal anterior flagella

• +/- chloroplasts (3 membrane envelope)

• able to grow autotrophically or heterotrophically

photosynthetic euglenoidFigure 28-11

Protist Phylogenies

• The Euglenozoa– Kinetoplastids

• have a single large mitochondrion• with DNA in a kinetoplast

–DNA minicircles & maxicircles»maxicircles encode proteins»minicircles encode editorial guides

• includes many pathogens–sleeping sickness, leishmaniasis, etc.

parasitic kinetoplastidFigure 28-12

Protist Phylogenies

• The Alveolata– Dinoflagellates [Pyrrophyta]

• unicellular, mostly marine, mostly photosynthetic

• two flagella in perpendicular grooves• common endosymbionts esp. in sponges• some secondarily heterotrophic parasites• some cause red tides• many are bioluminescent

Dinoflagellate red tideFigure 28-13

Protist Phylogenies

• The Alveolata– Apicomplexans

• obligate parasites

• complex life cycles

–asexual and sexual reproduction

–two or more hosts

Figure 28-14

Protist Phylogenies

• The Alveolata– Ciliates

• possess short, hair-like cilia

• mostly heterotrophic

• highly specialized body form

• possess two types of nuclei

–1-1000 macronuclei - expression

–1-80 micronuclei - recombination

CiliatesFigure 28-15

ParameciumFigure 28-16

Protist Phylogenies

• The Alveolata– Ciliates

• Paramecium - genetic recombination without reproduction–conjugation recombines the genomes of

two cells–reproduction does not accompany

conjugation–non-conjugating clones eventually die

Paramecium conjugation Figure 28-17

Protist Phylogenies

• The Stramenopiles– protists bearing two unequal flagella, one

with tubular hairs (and their descendants)– two photosynthetic groups, one

heterotrophic group– the “brown plant” kingdom

DiatomsFigure 28-18

Protist Phylogenies

• The Stramenopiles– Diatoms [Bacillariophyta]

• single-celled, non-flagellated• produce chrysolaminarin and oils• many produce cell walls containing silica• asexual reproduction reuses cell walls• sexual reproduction creates new walls

diatom reproductionFigure 28-19

Protist Phylogenies

• The stramenopiles– brown algae [Phaeophyta]

• multicellular thalli or branched filaments• fucoxanthin (carotenoid) pigment• some are very large• some have tissue and organ differentiation• all exhibit alternation of generations

–some isomorphic, some heteromorphic

alternation of generationsFigure 26-22

Protist Phylogenies

• The stramenopiles– Oomycetes - water molds, mildews, etc.

• heterotrophic, coenocytic• many are saprobes, some plant parasites• cell walls contain cellulose• produce flagellated gametes

a water moldFigure 28-23

Protist Phylogenies

• Rhodophyta - the Red Algae– mostly multicellular, marine– chloroplasts contain phycoerythrin &

phycocyanin– produce floridean starch– produce no flagellated motile cells– some are source of agar– ancestors became chloroplasts in brown

algae & diatoms

red algae Figure 28-24

Protist Phylogenies

• Chlorophyta - one of two green algae clades– large, diverse group– varied growth forms

• unicellular, flagellate• colonial• filamentous• membranous

isomorphic life cycle of UlvaFigure 28-26

Protist Phylogenies

• Chlorophyta - one clade of green algae– large, diverse group– varied life cycles

• isogamous or anisogamous• isomorphic or heteromorphic• haplontic, diplontic or two multicellular generations

heteromorphichaplontic life cycle

of Ulothrix

Figure 28-27

Protist Phylogenies

• Charophytes– the other green algae clade

• smaller, less diverse than chlorophytes• sister group (outgroup) to plants

Charophytes, Figure 29-3

Protist Phylogenies

• Choanoflagellida– flagellated, colonial– cells resemble most common type of sponge

cell– may be closest protist relative of animals

Figure 28-28

radiolarian and heliozoanFigure 28-30

Protist Phylogenies

• Recurring body plans– pseudopodia are produced in several groups

• amoeboid pseudopodal locomotion arose in several groups

• actinopods–radiolarians and heliozoans produce

thin stiff pseudopods• foraminiferans produce thin, branched pseudopods & calcium carbonate shells

Protist Phylogenies

• Recurring body plans– slime molds

• three groups share superficial similarities but represent different lineages–acellular forms produce coenocytic

sheets–under harsh conditions, sclerotia or

sporangia form

Figure 28-31

Protist Phylogenies

• Recurring body plans– slime molds

• three groups share superficial similarities but represent different lineages–cellular forms consist of populations of

amoeboid cells–under harsh conditions, cells aggregate

into a pseudoplasmodium and fruiting body

Figure 28-32

Table 28-1