Protists

Protists

Any member eukaryotic that are unicellular microscope organisms (share morphological physiological characteristics with animals/plants or both).

Eukaryotic Cell Structure

Cytoskeleton; microtubules; flagella, cilia & centrioles; microfilaments; chloroplasts.

Microtubules

Crucial & found in all eukaryotes. Major components of cytoskeleton. Involved in mitosis, cell motility, intracellular transport, & maintenance of cell shape. Composed of alpha & beta-tubulin subunits assembled to linear protofilaments.

Flagella

Long, hair-like structure that extend from the plasma membrane and are used to move an entire cell (i.e. sperm)

T or F: Centrioles are absent in fungi, conifers & flowering plants, which do not have flagellated cells.

True

Microfilaments (=actin & myosin filaments)

Consists of 2 intertwined strands of Actin proteins & Myosin protein. Smallest filaments of the cytoskeleton. Have a vital role in cell movements, cell division & muscle contraction.

\--- are key to eukaryotic --- & -- movement.

Microtubules; flagella; cilia

\--- also produce cell movement.

Microfilaments (actin) & myosin motor proteins

Chloroplasts

Produce energy through photosynthesis & oxygen-release processes, which sustain plant growth. Are responsible for the biosynthesis of active compounds (i.e. amino acids). Mode of nutrition in eukaryotes.

Chemo-heterotrophs: Absorptive

Monomers cross plasma membrane by diffusion/active transport.

Chemo-heterotrophs: Ingestive

Particles taken into cell by phagocytosis followed by intracellular digestion. Food taken into digestive cavity, followed by extracellular digestion.

A heterotrophic prokaryote gained nucleus & ER from --- --- ---.

infolded plasma membrane

How Prokaryotes gained Mitochondria to develop into Eukaryotes?

Mitochondrion gained from endosymbiosis of aerobic heterotrophic bacterium.

What is endosymbiosis?

Mitochondria & chloroplast likely evolved from engulfed prokaryotes that once lived as independent organisms. This eukaryotic cell engulfed an aerobic prokaryote, which then formed an endosymbiotic relationship with the host eukaryote, gradually developing into a chloroplast.

How Prokaryotes gained Plastids to develop into Eukaryotes?

Unique plastids came from eukaryotic, symbiotic alga cells thru secondary endosymbiosis

Plastids that contain chlorophyll pigment

Chloroplasts

Unicellular

Entire life cycle as single cell. Diverse organelle: diverse forms.

Colonial

Daughter cells remain connect together. Share resources. Some specialized, but changeable, roles.

Multicellular

Cell specialization, interdependence. Cell junctions. Cell communication & coordination.

Multinucleate

Nuclear division without cytokinesis.

Eukaryotic Reproduction

Asexual (via mitosis, budding, fragmentation or regeneration) & Sexual.

Mitosis (Asexual Reproduction)

A process where a single cell divides into 2 identical daughter cells (cell division).

Budding (Asexual Reproduction)

A process in which a new organism develops from a bud of an existing organism.

Can some eukaryotes reproduce both sexually & asexually?

Yes! For example, organism A switches to sexual reproduction when moisture or available N is low. Zygote has a coating that lets its remain dormant even without moisture.

Fragmentation (Asexual Reproduction)

A process in which a piece of the body, or fragment, of the parent breaks off and develop into an independent offspring.

T or F: Sexual reproduction meiosis & fertilization separate haploid and diploid phases.

True

Where are most protist found?

Most are aquatic or live in moist tissues.

4 Supergroups of Eukaryotes

* Excavata
* SAR (Stramenopiles, Alveolata, Rhizaria)
* Archaeplastida (incl. land plants)
* Unikonta (incl. animals and fungi)

Excavata

* Diplo-monads
* Para-basalids
* Eugleno-zoans

\
*All are unicellular, flagellated, have no cell wall.*

Diplomonads

Unicellular; multiple flagella; no cell wall. Anaerobic; reduced mitochondria. Most are parasitic & can cause well-known diseases.

Example of Diplomonads

Girdia, which is a parasitic organism that causes Giardiasis (diarrheal illness). Victim swallow cyst in untreated water. One of the most common causes of waterborne disease.

How do Diplomonads reproduce?

By asexual method (=mitosis & cytokinesis)

Para-basalids

Unicellular; multiple flagella; no cell wall. Anaerobic; reduced mitochondria, asexual. Most are symbiotic.

Example of Para-basalids

Trichomonas vaginalis - human vaginal parasite (STD)

Eugleno-zoans

Unicellular; no cell wall; flagella with crystalline rod.

Example of Eugleno-zoans

Trypanosoma, which is a blood parasite that causes “sleeping sickness” (carried by tse-tse fly)

Stramenopiles (**S**ARs)

* Diatoms
* Brown Algae
* Oomycetes

Diatoms

Unicellular phytoplankton (“algae”). Key primary producers (aquatic) with yellow & brown accessory pigments. Silica walls (glass-life), life a petri dish. No flagellum except in gamete.

Brown Algae

Multicellular, mostly marine “seaweeds”. Major 1° producers with brownish accessory pigments. Large thallus form. Cell wall with cellulose & algin.

Oomycetes

Filamentous, multinucleate, heterotrophs; some infect plants. Superficially resemble fungi but have cell walls with cellulose, not chitin. Filamentous growth is diploid.

Dinoflagellates

Unicellular aquatic heterotroph or phytoplankton with reddish accessory pigments. Pair of flagella in perpendicular grooves. Many with internal cellulose plates. Many are photosynthetic mutualists within corals.

Apicomplexans

Unicellular, parasites of animals; no cell wall. Apical complex helps them enter host cells. Complex life cycles - requires more than one host.

Example of Apicomplexans

Plasmodium causes malaria & are carried by mosquitos.

Ciliates

Unicellular ingestive (taken into body by mouth) heterotroph with no cell wall; aquatic. Cilia for feeding & locomotion. Almost all ciliates are “free-living”, feeding on bacteria & algae.

Ciliates Reproduction

Most reproduction is asexual division. Both macronucleus (polyploid; controls cell functions) & micronucleus (used only for genetic recombination) divide.

Rhizaria (SA**R**s)

* Radio-larians
* Forami-niferans (“Forams”)

Radiolarians

Unicellular marine plankton. Feed with threadlike pseudopodia. Symmetric silica “skeletons”.

Foraminiferans (“Forams”)

Unicellular, mostly marine plankton. Feed with threadlike pseudopodia. Porous shells (tests) of calcium carbonate. Most are “ingestive” heterotrophs” but some are mutualists with algae.

Archaeplastida

* Red Algae
* Chlorophytes

Archaeplastida

Chloroplasts from primary endosymbiotic event. Have cell walls, all include cellulose.

What do all Archaeplastida have in common?

Plastids derived from primary endosymbiosis.

Red Algae

Mostly marine, multicellular seaweeds. Chloroplasts include unique red phycoerythrin accessory pigment, which is why it is red - helps absorb light in deeper water.

Chlorophytes

Have “green algae” (along with Charophytes). Chloroplasts same as in plants. Most are freshwater; many marine. Many with bi-flagellated cells. Some of unicellular. Many are multicellular.

Unikonta

* Amoebo-zoans
* Opistho-konts

Amoebozoans

* Slime Molds
* Tubulinids
* Entamoebas

Slime Molds

Live in moist terrestrial habitats (rotting wood, etc.). Use pseudopodia to move & ingest bacteria. Produce stalked, spore-producing “fruiting” bodies when conditions are harsh.

Plasmodial Slime Molds (Method 1 of Feeding)

Slime molds feed a multinucleate plasmodium (=a mobile multinucleate mass of cytoplasm without a fire cell wall).

Cellular Slime Mold (Method 2 of Feeding)

Feed as single cells then gather as an “aggregate” when food is gone to form spores.

Tubulinids

Body like a tube. Unicellular, free-living. Aquatic or moist terrestrial. move with pseudopodia, feeding on bacteria, other protists, detritus.

Entamoebas

Unicellular parasites of animals. Kills & feeds on host cells. Spread by durable cyst form.