Kingdom Protista

The Link Between Bacteria and the Multicellular World

• There are plant-like protists that photosynthesize– Dinoflagellates– Euglena– Diatoms– Algae

The Link Between Bacteria and the Multicellular World

• Some are carnivorous protists that are hunters– Amoebas– Ciliates

The Link Between Bacteria and the Multicellular World

• Finally, some are like fungus, because they absorb nutrients from the surroundings and produce spores.– Slime molds.

Protist: Characteristics

• All are Eukaryotic• Some motile, some not• Some single-celled, some

multicellular.• Variety of Ways to Get Energy

– Some are• Carnivorous• Photosynthetic• Chemoautotrophic• Detritivores

Characteristics

• Reproduction– Primarily Asexual

• Budding• Fragmentation• Spores

– Sexual (less common but does happen)• Many events happen in times of stress• Male + Female gametes• Sometimes, protists

Protista: General

Characteristics

diplomonadsparabasalids

Flagellated Protozoans

trypanosomeseuglenoids

radiolariansforaminiferans

prokaryotic ancestor

ciliatesdinoflagellates

Alveolates

apicomplexans

water moldsdiatoms Stramenopilesbrown algae

red algae

chlorophyte algae Green Algae

charophyte algaeland plants

amoebas Amoebozoansslime molds

fungi

choanoflagellatesanimals

Classification and Phylogeny

Figure 22.2

Single-celled protists include (a) amoebas, (b) euglenoids, and (c) diatoms. Most red algae (d) and all brown algae (e) are multicelled. (f) One proposed eukaryotic family tree with traditional protist groups indicated by tan boxes. Notice that the protists are not united as a single lineage.

Figure It Out: Are land plants more closely related to the red algae or the brown algae?

Answer: red algae

Group: Flagellated Protozoans

• Flagellated protozoans are single-celled protists covered by a pellicle (proteins that help cells retain shape)

• They swim in lakes, seas, and the body fluids of animals

• They are typically heterotrophic and reproduce asexually by binary fission

Trypanosomes and Other Kinetoplastids• Kinetoplastids are flagellated

protozoans with a single large mitochondrion

• Trypanosomes include human pathogens that are transmitted by insects– African sleeping sickness (T. brucei) is

spread by tsetse flies– Chagas disease (T. cruzi) is spread by

bloodsucking bugs

Human DiseaseTrypanosoma

•African sleeping sickness

•Transmitted by tsetse fly

•Causes fever, mental deterioration and coma

Phylum Zoomastigina

•No means of locomotion- most are parasitic and don’t need it

•Sexual reproduction present

•Environment- parasitic-aquatic

Human DiseaseGiardia•Causes giardiasis

•Sever diarrhea and intestinal cramps

•Parasite in contaminated water

•Thousands of cases annually in U.S.

•Not usually fatal, but, you can imagine, uncomfortable.

                               

A SEM micrograph of the small intestine of a gerbil infested with Giardia reveals a mucosa surface almost entirely obscured by attached trophozoites

The Euglenoids• Euglenoids are flagellated protists

related to kinetoplastids that do not infect humans– Most prey on bacteria– Some have chloroplasts that evolved from

green algae and can detect light with an eyespot

– Most live in freshwater and have contractile vacuoles that expel excess water

Foraminiferans & Radiolarians

• Heterotrophic single cells with chalky or glassy shells live in great numbers in the world’s oceans; cytoplasm extends through many pores.

• Most forams live on the seafloor; others drift as part of the plankton.

Phylum Actinopoda

• Radiolarians• Silica test • Pseudopodia

used for food getting

• Asexual reproduction

• Mostly marine

Phylum Foraminifera

Forams

•Locomotion and food getting by pseudopodia

•Calcium carbonate test

•Environment- primarily marine

Group: Alveolates/ Ciliates

• Ciliates are heterotrophic single cells that move about with the help of cilia

• Ciliates reproduce asexually by binary fission or sexually by conjugation.

Phylum Ciliophora• Locomotion and

food getting by cilia • Pellicle present

maintains shape • Contractile vacuoles

remove excess water

• Sexual reproduction by conjugation

• Environment- aquatic

• Heterotrophic & parasitic

Paramecium•Unicellular•Heterotrophic•Cilia•Requires oxygen to live = aerobic environment•Asexual & Sexual Reproduction•Special Quality

2 nucleii•Found in most aquatic environments

Phylum Ciliophora

Stentor•Largest freshwaterprotozoan•Can regenerate body parts•Cilia covers bodyfor movement & feeding

Phylum Ciliophora

Didinium

This organism is aggressive and has a

huge appetite

Didinium feedingAttaches to paramecium

Starts to ingest

Almost completely engulfed

Phylum Apicomplexa•Protozoan that causes malaria •Plasmodium enters bloodstream, travels to liver cells, where they divide and release new spores into the bloodstream. •Parasitic•No locomotion•Reproduce asexually•Transmitted by bite of infected mosquito•Destroys red blood cells

Group: Stramenopiles • “Red Algae”• Brown algae are

multi-celled protists that live in temperate or cool seas; ranging from microscopic filaments to giant kelp

• Some brown algae are used commercially– Thickeners (algins),

food, fertilizer, herbal supplements (bladderwrack)

Diatoms

• Diatoms are single-celled or colonial protists that have a two-part silica shell – Shells accumulate on

the seafloor (diatomaceous earth)

• Most are photosynthetic, with a brown accessory pigment (fucoxanthin) – Major components of

phytoplankton

Group: Red Algae • Red algae are mostly multi-

celled marine algae that live in clear, warm waters

• Red accessory pigments (phycobilins) allow red algae to live at greater depths than other algae

• Red and green algae share a common ancestor with chloroplasts derived from cyanobacteria

• Life cycles vary and are often complex, with both asexual and sexual phases; there is no flagellated stage.

Group: Green Algae

• Most green algae are chlorophytes– Chlorella: Single celled, grown as health food– Chlamydomonas: Single celled, freshwater

alga– Volvox: Colonial, freshwater alga– Cladophora: Forms long filaments– Ulva: “Sea lettuce”– Codium fragilis: Branching marine alga

• Charophyte algae include several lineages that form a clade with land plants– Desmids: A single-celled,

freshwater group– Spirogyra: Forms long

filaments– Stoneworts (Chara):

Closely related to land plants

Group: Amoebozoans• Amoebozoans send out pseudopods,

move about, and capture food– Most have no cell walls, shell, or

pellicles• Amoebas live as single cells

– Example: Amoeba proteus, a freshwater predator

• Slime molds are “social amoebas”– Plasmodial and cellular slime molds

• Plasmodial slime molds spend most of their lives as a plasmodium– A streaming multinucleated

mass that feeds on microbes and organic matter

– Undergoes mitosis many times without cell division

– Develops into spore-bearing fruiting bodies

Phylum: Sarcodina• Unicellular• Have pseudopodia =

“false foot” which is an extension of the cytoplasm

• Pseudopodia for locomotion & feeding

• Reproduce asexually• Most are free-living,

some parasitic• Found in soil, marine

and freshwater

Amoebas

Amoeba Structure

Amoeba locomotion & feeding

• Endocytosis (Phagocytosis)

• Digestion by enzymes

• Distinguish between food and non-food

Recap

• Protists represent the kingdom where evolutionary adaptations allowed for the development of plants, fungus, and animals from single-celled bacteria.

• Protists have numerous characteristics that allow for grouping.

• Some protists are good for us: provide nutrients, photosynthesize, etc.

• Some protists cause disease: malaria, African sleeping sickness, giardiasis.