Introduction to Protists Origins of Eukaryotic Diversity Chapter 28 Introduction to Protists

Origin of Eukaryotes 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 Eukaryotic cell more complex than prokaryotic cell: 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.

Prokaryotic Cells

Eukaryotic Animal Cell Typical Animal Cell

Eukaryotic Plant Cell Typical Plant Cell

Animal Vacuole Functions vacuole Plant mitochondria chloroplasts Storage Support Water Regulation vacuole Plant mitochondria chloroplasts Both cell types have membrane-bounded organelles

Origin of Eukaryotes Endomembrane infolding Infolding of membrane system forming nucleus and ER

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 A B C D Cyanobacteria Aerobic bacteria Mitochondria Chloroplasts N N N Plant cell Prokaryote N Animal Cell

Endosymbiosis Hypothesis Over a long period of time the aerobes became mitochondria, no longer able to live on their own A B C D Cyanobacteria Aerobic bacteria Mitochondria Chloroplasts N N N Plant cell Prokaryote N Animal Cell

Endosymbiosis Hypothesis C Some primitive prokaryotes also ingested cyanobacteria, which contain photosynthetic pigments A B C D Cyanobacteria Aerobic bacteria Mitochondria Chloroplasts N N N Plant cell Prokaryote N Animal Cell

Endosymbiosis Hypothesis Cyanobacteria became chloroplasts, unable to live on their own A B C D Cyanobacteria Aerobic bacteria Mitochondria Chloroplasts N N N Plant cell Prokaryote N Animal Cell

Secondary Endosymbiosis and Origin of Algal Diversity Algae AB N N Secondary endosymbiosis N Heterotroph C Algae ABC Many membrane layers

Secondary Endosymbiosis Fig. 28-02-2 Secondary Endosymbiosis Plastid Dinoflagellates Secondary endosymbiosis Apicomplexans Cyanobacterium Red alga Primary endosymbiosis Stramenopiles Heterotrophic eukaryote Plastid Secondary endosymbiosis Over the course of evolution, this membrane was lost. Euglenids Secondary endosymbiosis Green alga Chlorarachniophytes

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

Common ancestral community of primitive cells model All three domains seem to have genomes that are chimeric mixes of DNA that was transferred across the boundaries of the domains.

Fig. 28.8 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Five Supergroups Excavata Chromalveolata Rhizaria Archaeplastida Euglenoids Chromalveolata Dinoflagellates, diatoms, golden and brown algae Rhizaria Forams and radiolarians Archaeplastida Red and green algae Unikonta Slime molds

Plantae Fungi Animalia Kingdom Protista Plantae Fungi Animalia Protista Monera prokaryotic eukaryotic

Kingdom Protista Eukaryotic Mostly unicellular A very heterogeneous group include both heterotrophic and photoautotrophic forms 11 phyla Lots of disagreements Whittaker = “leftovers”

Reproduction: binary fission splits into two asexually multiple fission producing more than two individuals sexually by conjugation (opposite mating strains join & exchange genetic material) 

Kingdom Protista 3 informal groups Animal-like protists Fungus-like protists Plant-like (algal) protists Misleading: some change ~ 45,000 species

Kingdom Plantae Kingdom Animalia Kingdom Fungi Kingdom Protista Chlorophyta Ciliophora Myxomycota Phaeophyta Mastigophora Rhodophyta Chrysophyta Sarcomastigophora Euglenophyta Apicomplexa Pyrrophyta Kingdom Protista

Animal-like Protists Amoeba Cilliates Flagellates 13,000 species

Animal-like Protists Classified by the way they move pseudopodia cilia flagella

Heterotrophs ingest small food particles & digest it inside food vacuoles containing digestive enzymes Paramecium consume nutrients from other organisms. Their diet is bacteria, algae, yeast and other micro-organisms. It uses its cilia (strand or tail) and consumes the substance along with water from the mouth of the paramecium. The food enters the gullet or stomach and is stored there. After the gullet is full, the food breaks away and creates a vacuole along with the water. The vacuole moves through the cell, enzymes break down the substance from the inside by entering the vacuole. The nutrients are removed from the vacuole into the cell and the cell gets smaller until it gets released from the cell as waste. Paramecium are interesting cause they eat micro-organisms and even resort to cannibalism. The protist kingdom is very diverse so it is hard to put comparisons on one another without a base.

Animal-like protists Sarcomastigophora (amoebas, forams, radiolarian) Ciliophora (paramecium) Zoomastigophora (trypansoma) Apicocomplexa (Sporozoa)

Animal-like Protists Phylum Sarcomastigophora “Amoeba” Shell-like glass or calcium carbonate structures Radiating projections 13,000 species

Note: glass projections

Foraminifera Tropics = beaches Most have symbiotic algae

Foramenifera: Globigerina ooze Covers about 36% of the ocean floor

Animal-like Protists Phylum Ciliophora (“ciliates”) Largest, most homogeneous Share few characteristics with others Movement coordinated Sex: 8 mating types 8,000 species

Paramecium

Plant-like Protists Dinoflagellates Diatoms Euglena Cocolithophore Green algae Brown Algae Red algae Dinoflagellates Cocolithophore Radiolarian

Plant-like Protists Phylum Pyrrophyta (“dinoflagellates”) Marine and Freshwater Some live in corals Cause “red tide” 1,100 species

Zooxanthellae in Coral Polyp

Bioluminescence Pyrocystis fusiformis

Plant-like Protists Phylum Chrysophyta (“diatoms & golden algae”) Link to green algae 13,000 species

Plant-like Protists Phylum Euglenophyta (“euglenoids”) 800 species

Division Chlorophyta “Green algae” Most freshwater or terrestrial Some marine 7,000 species

Chlorophyta: Green Algae Halimeda opuntia Codium edule Caulerpa sertularioides Dictyosphaeria cavernosa Caulerpa racemosa

Division Phaeophyta “Brown algae” Marine habitats Example: giant kelp forests 1,500 species

Example of complex morphology: Macrocystis holdfast - attaches to substrate stipe blade - main organ of photosynthesis bladder - keeps blades near the surface Blade Bladder Stipe Holdfast

Laminaria Life Cycle

Phaeophyta: Brown Algae Turbinaria ornata Padina japonica Hydroclathrus clathratus Sargassum echinocarpum Sargassum polyphyllum

Division Rhodophyta “Red algae” Most in marine habitats 4,000 species

Rhodophyta: Red Algae Ahnfeltia concinna Acanthophora spicifera Hypnea chordacea Galaxaura fastigiata Asparagopsis taxiformis

Herbivores

Algal Invaders Halimeda opuntia Acanthophora Gracilaria Hypnea Avrainvillae Kappaphycus Eucheuma

Super Sucker

Inquiry Identify 2 organisms that have a mutualistic symbiotic relationship with an other organism. Read pages 510 – 514 Chpt 20 Alternation of Generations ( two examples)