Kingdom Protista

Kingdom Protista

Kingdom Protista

• Kingdom Protista - 65,000-200,000 species (est.), fr. Greek protos = first, ktistos = established - algae, protozoans

• Also called Kingdom Protoctista

• Taxonomic “grab bag”, primitive organisms only distantly related (polyphyletic)

Kingdom Protista

• All protists are eukaryotes

• All protists are aquatic

• Unicellular or multicellular

• Some are colonial - cells specialize in different function (feeding, reproduction) = division of labor, communication

Kingdom Protista

• Some are autotrophs = algae

• Some are heterotrophs = protozoa

• Reproduce either sexually or asexually (by binary fission)

• Complex life cycles

Kingdom Protista

• Protists are so small they don’t need special organs to exchange gas or excrete wastes

• They rely on diffusion - passive movement of molecules from area of higher concentration to area of lower concentration

• Diffusion results from the random movement of molecules

Kingdom Protista

• Diffusion is a two edged sword

• Protists don’t need to invest in complex respiratory or excretory tissue

• They have to stay tiny - diffusion only works if you’re very small

• Most protists are single cells

Kingdom Protista

• Size is also limited by means of locomotion

• Many protists are propelled by cilia or flagella, tiny movable hairs

• Protists eat by phagocytosis

> Engulf food in cell membrane

> Pinch off membrane to form a vacuole

> Vacuoles store food, water, enzymes, wastes

Phagocytosis

Didinium devours Paramecium

Kingdom Protista

• All of these traits are primitive - similarities may be due to convergent evolution

• Protists are mainly defined by what they are not

> Not bacteria, archaea, or fungi…

> Not plants or animals…

Kingdom Protista

• Protists gave rise to all other plants and animals

• Phylogeny of protists still a real mess

• We assume they rose from certain groups of archaeans, but which?

Kingdom Protista

• Protists are so different from one another, most may represent several early independent lineages of eukaryotes

• First evolved ~ 1.2 billion years ago

• As many as 50 phlya recognized

• We’ll focus on several typical phyla

Kingdom Protista

• Protozoa - heterotrophs

> Motile

– Cilia – Ciliophora

– Flagella – Dinoflagellata, Euglenozoa

– Pseudopodia – Amoebozoa, Foraminifera

> Non- motile - Apicomplexa

• Gave rise to higher animals

Kingdom ProtistaPhylum Euglenozoa

• 800 sp. - Euglena

• Plant or animal? Heterotrophs, but 1/3d are also photosynthetic

• May have formed by endosymbiosis, engulfed green algae cell

Euglena

Euglena

Kingdom ProtistaPhylum Dinoflagellata

• Dinoflagellates - 3,000 species, fr. Greek dinos = whirling, Latin flagellum = whip - Ceratium, Gonyaulax

• About half are photosynthetic

Dinoflagellates

Kingdom ProtistaPhylum Dinoflagellata

• Two flagella, one like a belt, one like a tail

• Many have armor of cellulose plates encrusted with silica

Dinoflagellates

Kingdom Protista Phylum Dinoflagellata

• Importance

> Zooxanthellae, dinoflagellates that have lost flagella & armor, live as symbionts in mollusks, sea anemones, jellyfish, coral

> Make coral more productive, limits coral to shallow water

Kingdom Protista Phylum Dinoflagellata

• Importance

> Algal blooms of dinoflagellates are the cause of red tide - 20 species produce potent toxins

> 1987 outbreak killed half the Western Atlantic population of bottlenose dolphin!

> Could make La. oysters an unforgettable experience…

Red Tide 2010 Breton-Chandeleur

Kingdom ProtistaPhylum Apicomplexa

• Apicomplexa are spore-forming parasites

• One end has an apical complex, apparatus designed to let them invade a host cell

• Sometimes called sporozoans, many form non-motile spores

Kingdom ProtistaPhylum Apicomplexa

• Plasmodium – causes malaria

• Spores are passed from one host to the next by vectors (mosquitoes etc.)

• Typical parasite life cycle, with intermediate hosts

Kingdom ProtistaPhylum Ciliophora

• 8,000 species, fr. Latin cilium = eyelash, Greek phorein = to bear - Paramecium, Blepharisma

• Complex little critters - many organelles and specialized structures

Blepharisma

Kingdom Protista

• Paramecium (and many other protists) have a contractile vacuole

• Complex vacuole that drains wastes from the cell

Contractile Vacuole of Paramecium

Kingdom ProtistaPhylum Ciliophora

• Move by numerous cilia

• Many ciliophorans defend themselves by discharging little toxic threads or darts

Paramecium, with cilia stained

Kingdom ProtistaPhylum Ameobozoa

• Over 300 species – true amoeba

• Move by pseudopods - extend part of cell to form a “false foot”, then flow into it (cytoplasmic streaming)

• Eat other protozoans, algae, even tiny multicellular creatures

Amoeba

Kingdom Protista Phylum Ameobozoa

• Many amoeba are parasites

> Entamoeba histolyca - amoebic dysentery, infects ~10 million Americans, 50% of population in the tropics


• Many amoeba are parasites

> Primary Ameobic Meningoencephalitis (PAM) Naegleria fowleri enters the nostrils (frequently during swimming), attacks the brain, can be fatal within one week of symptoms

> PAM is relatively rare -120 U.S. cases in 25 years


• PAM cases include two people in La. in 2011 who died from nasal irrigation with infected water (has to go way up the nose)

• PAM killed a 4 year old child in LA in 2013 who got it from playing on a Slip ‘n Slide

• Later found in the municipal water supply in Arabi and Violet (a first) – easily killed by chlorination

Kingdom Protista Phylum Foraminifera

• Foraminifera

> Marine forms, sculpted shells (calcium carbonate)

> Extend cytoplasmic podia out along the spines

> Spines function in feeding, swimming

Kingdom Protista Phylum Foraminifera

• Importance

> So abundant, they formed most of the world’s limestone, marble, and chalk

> Great Pyramids composed of billions upon billions of foraminiferan shells

> Abundant in fossil record, used by geologists to help identify layers of rock - indicator species

Foraminiferan shells

Great Pyramids of Egypt

Kingdom Protista

• Algae – autotrophic protists

> Photosynthetic

> Many referred to as “seaweeds”

> Gave rise to higher plants

• Phaeophyta, Bacillariophyta, Rhodophyta, Chlorophyta

Brown Algae - Fucus - rockweed

Kingdom ProtistaPhylum Phaeophyta

• Brown algae - 1,500 species, fr. Greek phaios = brown - Fucus, Sargassum, kelp

• Mostly marine

Kelp


• Largest protists, kelp up to 100 meters long

• Blades lack conducting tissue, rely on diffusion - can be large but must be thin

Brown Algae - Kelp

Brown Algae - Saccorhiza polyschides


• Importance

> Kelp forms the basis for major ecosystem along the Pacific Coast and in other cool waters

> Sargassum forms large floating mats in the Atlantic, northeast of the Caribbean, a major ecosystem - Sargasso Sea once thought to trap ships

Kelp

Kingdom ProtistaPhylum Baccilariophyta

• Diatoms - 11,500 species

• Golden-brown pigment

Kingdom ProtistaPhylum Baccilariophyta

• Abundant in freshwater and marine habitats

• Shells made of organic compounds impregnated with silica (CD jewel case)

Kingdom Protista Phylum Baccilariophyta

• Importance

> So abundant they account for a large percentage of the oxygen added to the atmosphere

> Shells form deposits called diatomaceous earth, used in abrasives, talc, and chalks

> Lompoc CA quarry - 270,000 metric tons/year, Santa Monica bed is over 900 meters thick!

Kingdom ProtistaPhylum Rhodophyta

• Red algae - 4,000 species, fr. Greek rhodos = red - Polysiphonia, Nemalion

• Mostly marine, closely related to green algae

• Red algae dominate in salt water, green algae dominate in fresh water

• Elaborate life cycles


• Red algae plastids (rhodoplasts) similar to certain cyanobacteria, acquired through endosymbiosis

• Brown algae formed in similar fashion, eukaryotic protist swallowed a red algae

Red Algae - Scinaia furcellata


• Importance

> Agar from cell walls used for culture plates

> Carrageen, thickening agent also extracted from red algae, used in making ice cream, lunch meats, cosmetics, paint, beer and wine!

Kingdom ProtistaPhylum Chlorophyta

• Green algae - ancestral to land plants

• Recently recognized as sister taxon to land plants

• Now “bumped up” to Kingdom Viridiplantae (algae + land plants)

Chlorophyta

Documents

Kingdom Protista