Introduction to Protists. First eukaryotic organism thought to have evolved about 1.5 billion years ago Protozoans possible evolved from the 1 st eukaryotes.

Introduction to Protists

• First eukaryotic organism thought to have evolved about 1.5 billion years ago

• Protozoans possible evolved from the 1st eukaryotes by Endosymbiosis

• Endosymbiosis – process where one prokaryote lives inside another becoming dependent upon each other

Origin of Eukaryotes

• Membrane-bound nucleus and organelles

• Chromosomes consist of DNA and histone proteins and occur in pairs.

• Protists, fungi, plants & animals are composed of eukaryotic cells.

Origin of EukaryotesEukaryotic cell more complex than prokaryotic cell:

Prokaryotic Cells

Typical Animal Cell

Eukaryotic Animal Cell

Typical Plant Cell

Eukaryotic Plant Cell

Animal

Plant

mitochondria

chloroplasts

vacuole

Vacuole Functions• Storage• Support• Water Regulation

Both cell types havemembrane-bounded organelles

Infolding of membrane system forming nucleus and ER

Origin of Eukaryotes

Endomembrane infolding

Origin of Eukaryotes

Evolution of eukaryotic cell- Endosymbiosis

• Theory proposed by Mereschkovsky and refines by Margulis- serial endosymbiosis• Mitochondria and plastids were

prokaryotes that invaded larger cells• Endosymbiont, ancestral

mitochondria:Aerobic, heterotrophic &

prokaryotic

Origin of Eukaryotes

• Ancestral chloroplasts were photosynthetic, prokaryotes that became endosymbionts

• Relationship began as parasitic or undigested prey

• Assumed here that endomembrane infolding evolved first, i.e., cell already evolved nucleus, ER, …

Endosymbiosis Hypothesis

A

A prokaryote ingested some aerobic bacteria. The aerobes were protected and produced energy for the prokaryote

ChloroplastsAerobic bacteria MitochondriaCyanobacteria

Prokaryote

Animal Cell

Plant cell

B C D

A

N

NN

N

Endosymbiosis Hypothesis

B Over a long period of time the aerobes became mitochondria, no longer able to live on their own

A B C D

ChloroplastsAerobic bacteria MitochondriaCyanobacteria

Prokaryote

Animal Cell

Plant cellN

NN

N

Endosymbiosis Hypothesis

C Some primitive prokaryotes also ingested cyanobacteria, which contain photosynthetic pigments

A B C D

ChloroplastsAerobic bacteria MitochondriaCyanobacteria

Prokaryote

Animal Cell

Plant cellN

NN

N

Endosymbiosis HypothesisD Cyanobacteria became chloroplasts,

unable to live on their own

A B C D

ChloroplastsAerobic bacteria MitochondriaCyanobacteria

Prokaryote

Animal Cell

Plant cellN

NN

N

Secondary Endosymbiosis and Origin of Algal Diversity

Algae AB

Heterotroph C

N

N

Secondary endosymbiosis

N

Many membrane layers

Algae ABC

Fig. 28-02-2

Cyanobacterium

Heterotrophiceukaryote

Over the courseof evolution,this membranewas lost.

Red alga

Green alga

Primaryendosymbiosis

Secondaryendosymbiosis

Secondaryendosymbiosis

Secondaryendosymbiosis

Plastid

Dinoflagellates

Apicomplexans

Stramenopiles

Plastid

Euglenids

Chlorarachniophytes

Secondary Endosymbiosis

LUCA model places the archaea as more closely related to eukaryotes than they are to prokaryotes.

• All three domains seem to have genomes that are chimeric mixes of DNA that was transferred across the boundaries of the domains.

Common ancestral community of primitive cells model

Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Fig. 28.8

Excavata

Chromalveolata

Rhizaria

Archaeplastida

Unikonta

Five Supergroups

Red and green algae

Slime molds

Forams and radiolarians

Dinoflagellates, diatoms, golden and brown algae

Euglenoids

Kingdom Protista

Plantae Fungi Animalia

Protista

Moneraprokaryoticprokaryotic

eukaryoticeukaryotic

Kingdom Protista

• Eukaryotic

• Mostly unicellular

• A very heterogeneous group include both heterotrophic and photoautotrophic forms

• 11 phyla

• Lots of disagreements

• Whittaker = “leftovers”

• binary fission splits into two asexually

• multiple fission producing more than two individuals

• sexually by conjugation (opposite mating strains join & exchange genetic material) 

Reproduction:

3 informal groups

Animal-like protists

Fungus-like protists

Plant-like (algal) protists

Misleading: some change

Kingdom Protista

~ 45,000 species

Ciliophora

Kingdom Animalia

Sarcomastigophora

Apicomplexa

Mastigophora

Euglenophyta

Kingdom Plantae

Chrysophyta

Pyrrophyta

Myxomycota

Kingdom Fungi

Kingdom Protista

Chlorophyta

Phaeophyta

Rhodophyta

Amoeba

Cilliates

Flagellates

Animal-like Protists

13,000 species

• Classified by the way they move

Animal-like Protists

cilia flagella pseudopodia

• Heterotrophs ingest small food particles & digest it inside food vacuoles containing digestive enzymes

Animal-like protists

• Sarcomastigophora (amoebas, forams, radiolarian)

• Ciliophora (paramecium)

• Zoomastigophora (trypansoma)

• Apicocomplexa (Sporozoa)

Phylum Sarcomastigophora

“Amoeba”

Shell-like glass or calcium carbonate structures

Radiating projections

Animal-like Protists

13,000 species

Note: glass projections

Foraminifera

Tropics = beaches

Most have symbiotic algae

Foramenifera:Globigerina ooze

Covers about 36%of the ocean floorCovers about 36%of the ocean floor

Phylum Ciliophora (“ciliates”)

Largest, most homogeneous

Share few characteristicswith others

Movement coordinated

Sex: 8 mating types

Animal-like Protists

8,000 species

Paramecium

Plant-like Protists

• Dinoflagellates• Diatoms• Euglena• Cocolithophore• Green algae• Brown Algae• Red algae

Diatoms

Dinoflagellates

Radiolarian

Cocolithophore

Plant-like Protists

Phylum Pyrrophyta (“dinoflagellates”)

1,100 species

Cause “red tide”

Some live in corals

Marine and Freshwater

Zooxanthellae in Coral Polyp

Pyrocystis fusiformis

Bioluminescence

Plant-like ProtistsPhylum Chrysophyta (“diatoms &

golden algae”)

Link to green algae

13,000 species

Phylum Euglenophyta (“euglenoids”)

Plant-like Protists

800 species

Division Chlorophyta

“Green algae”

Most freshwater or terrestrial

Some marine

7,000 species

Halimeda opuntia

Chlorophyta: Green Algae

Caulerpa racemosa

Caulerpa sertularioides

Dictyosphaeria cavernosa

Codium edule

Division Phaeophyta

“Brown algae”

Marine habitats

Example: giant kelp forests

1,500 species

Example of complex morphology: Macrocystis

a. holdfast - attaches to substrate

b. stipe

c. blade - main organ of photosynthesis

d. bladder - keeps blades near the surface

Blade

Bladder

Stipe

Holdfast

Laminaria Life Cycle

Sargassum polyphyllumSargassum echinocarpum

Phaeophyta: Brown Algae

Turbinaria ornata

Padina japonicaHydroclathrus clathratus

Division Rhodophyta

“Red algae”

Most in marine habitats

4,000 species

Hypnea chordacea

Asparagopsis taxiformis

Galaxaura fastigiata

Acanthophora spicifera

Ahnfeltia concinna

Rhodophyta: Red Algae

Halimeda opuntia

Acanthophora

Avrainvillae

Eucheuma

Gracilaria Hypnea

Kappaphycus

Super Sucker

Inquiry

1. Identify 2 organisms that have a mutualistic symbiotic relationship with an other organism.

2. Read pages 510 – 514 Chpt 20

3. Alternation of Generations ( two examples)