1

Protists

Protists• Characteristics

• A) Organelles

• B) Organizational structure

Endosymbiotic hypothesis

Protists are believe to be the oldest eukaryotes on the evolutionary tree.

2

Cyanobacterium

Heterotrophiceukaryote

Primaryendosymbiosis

Red algae

Green algae

Secondaryendosymbiosis

Secondaryendosymbiosis

Plastid

Dinoflagellates

Apicomplexans

Ciliates

Stramenopiles

Euglenids

Chlorarachniophytes

Plastid

Alve

olat

es

• Diversity of plastids produced by secondary endosymbiosis

Protists• Groups

• 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

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Kingdom Protista is

very diverse.

15 phyla, based on the way

they obtain energy.

• Protist habitats are also diverse. • And including freshwater and marine species

100 µm

100 µm

4 cm

500 µm

The freshwater ciliate Stentor,a unicellular protozoan (LM)

Ceratium tripos, a unicellular marine dinoflagellate (LM)

Delesseria sanguinea, a multicellular marine red alga

Spirogyra, a filamentous freshwater green alga (inset LM)

(a)

(b)

(c)

(d)

LE 16-19

Dip

lom

onad

s

Eugl

enoz

oans

Din

ofla

gella

tes

Api

com

plex

ans

Cili

ates

Wat

er m

olds

Bro

wn

alga

e

Gre

en a

lgae

Plan

ts

Clo

sest

alg

al re

lativ

es o

f pla

nts

Red

alg

ae

Ani

mal

s

Fung

i

Am

oeba

s

Cho

anof

lage

llate

s

Cel

lula

r slim

e m

olds

Plas

mod

ials

lime

mol

ds

Dia

tom

s

Alveolates Stramenopila Amoebozoa

Ancestral eukaryote

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Fig. 22-2, p.352

Groups (Phyla)

7 monophyletic groups

Parabasalids & Diplomonads

• Most primitive• Are adapted to anaerobic environments• Lack plastids• Have mitochondria that lack DNA, an

electron transport chain, or citric-acid cycle enzymes

Diplomonads• Diplomonads

– Have two nuclei and multiple flagella

5 µm(a) Giardia intestinalis, a diplomonad (colorized SEM)

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Once ingested by a host, the trophozoiteemerges to an active state of feeding and motility. It feeds on mucous inside the digestive tract and causes the host to have epigastric pain, excessive gas, and diarrhea with fat and mucous but no blood. This can last from 2 -4 weeks but for a lactose intolerant individual, it can last up to six months.

Diplomonads – 3+1 flagella

Giardia lamblia – intestinal parasite

Fig. 22-3b,c p.353

Parabasalids• Parabasalids include trichomonads

– Which move by means of flagella and an undulating part of the plasma membrane

Trichomonas vaginalis, a parabasalid (colorized SEM)

Flagella

Undulating membrane 5 µm

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Parabasalids--Heterotrophic flagellates

Trichomonas vaginalis

Fig. 22-3a, p.353

STD

Euglenoids & Kinetoplastids

• Single-celled flagellates• Have flagella with a unique internal

structure• A diverse clade that includes

– Predatory heterotrophs, photosynthetic autotrophs, and pathogenic parasites

• The main feature that distinguishes protists in this clade– Is the presence of a spiral or crystalline rod

of unknown function inside their flagella

Flagella 0.2 µm

Crystalline rod

Ring of microtubules

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Fig. 22-4b, p.354

Euglenoids

Euglena gracilis

mitochondrion

nucleus

long flagellum

chloroplast

Fig. 22-4a2, p.354

Euglenoids

Euglena gracilis

Phylum Euglenophyta

Freshwater

This phylum is a typical example of the difficulties in categorizing protists: 1/3 have chloroplasts, the other 2/3 do not.

No sexual reproduction. Longitudinal fission.

Propels the body through water.

For photosynthesis

Diversity of Kingdom Protista

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Kinetoplastids

• Kinetoplastids– Have a single, large mitochondrion that

contains an organized mass of DNA called a kinetoplast

– Include free-living consumers of bacteria in freshwater, marine, and moist terrestrial ecosystems

– Known best for its parasitic representatives

long flagellum attached to undulating membrane

single, longmitochondrion

Golgi body

vacuolenucleusER

Fig. 22-5a, p.355

Kinetoplastids -- Heterotrophs (parasites)

Fig. 22-5b, p.355

red blood cellundulating membrane attached to flagellum

Trypanosoma brucei --- sleeping sickness

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Trypanosomes- transmitted by the bite of a tsetse fly,

cause African Sleeping Sickness.

9 µm

Trypanosoma transferred by

Triatomine bugs (kissing bugs)

causes South American Chagas disease

Forams & Radiolarians

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Fig. 22-6, p.355

Forams & Radiolarians

Part of marine plankton

Foraminiferans (Forams)• Foraminiferans, or forams

– Are named for their porous, generally multichambered shells, called tests

20 µm

Foraminiferans (Forams)

• Pseudopodia extend through the pores in the test

• Foram tests in marine sediments– Form an extensive fossil record

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Radiolarians

• Radiolarians are marine protists….– whose tests are fused into one delicate

piece, which is generally made of silica– that phagocytose microorganisms with their

pseudopodia

• The pseudopodia of radiolarians, known as axopodia– Radiate from the central body

200 µm

Axopodia

Alveolates

Cillium/flagellumAlveoli0.2 µm

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Ciliated Alveolates

alveolus

cilium

Ciliates

• Ciliates, a large varied group of protists– Are named for their use of cilia to move and

feed– Have large macronuclei and small

micronuclei

Paramecium

Paramecium

Didinium

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food vacuole (being emptied)

gullet

cilia trichocysts

filled contractile vacuole

micronucleus

macronucleus

contractile vacuole emptied

Fig. 22-7c, p.356

Paramecium

intact trichocyst

Fig. 22-7a2, p.356

contractile vacuole

pellicle

Paramecium

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micronucleus

macronucleus

Fig. 22-7c, p.356

Paramecium

Fig. 22-8, p.357

Fig. 22-8n, p.357

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Flagellated Alveolates

• Dinoflagellates

Dinoflagellates

• Dinoflagellates– Are a diverse group of aquatic

photoautotrophs and heterotrophs– Are abundant components of both marine

and freshwater phytoplankton

Flagellated Alveolates• Dinoflagellates

Some are bioluminescent Some produce toxins