Chapter 28 (Protists)

Protists

A diverse group of mostly unicellular eukaryotes that do not fit into the animal, plant, or fungi kingdoms. They are more likely related to plants, animals, etc more, than they are to each other. Most are unicellular, the organisms in most eukaryotic lineages are protists.

Endosymbiosis

A relationship between two species in which one organism lives inside the cell of another organism (the host)

Eukaryotic supergroups

A large group of organisms that share a common ancestor and share a unique characteristic (Each supergroup has smaller groups within it)

Supergroup Excavata

Have an “excavated” feeding groove on one side of the body

Includes:

Diplomonads

Parabasalids

Euglenozoans

Diplomonad

Two nuclei + multiple flagella (unique cell structure)

Lacks mitochondria

Causes giardiasis

Giardia Infection (disease)

Intestinal infection marked by stomach cramps, bloating, nausea, and diarrhea

Spread through contaminated water

Also called (Backpackers Nightmare) A part of the Diplomonad protists

Parabasalid Protist

Parabasal organ (similar to the Golgi apparatus)

Also have reduced mitochondria (hydrogenosomes)

Characteristic undulating membrane + multiple flagella

Causes trichomoniasis

Trichomonas (disease)

One of the most common STD’s worldwide

Often asymptomatic → spreads silently

Part of the Parabasalid Protist

Euglenozoans

• Flagellated protists that include predatory heterotrophs, photosynthetic autotrophs, and pathogenic parasites

• A rod with either a spiral or a crystalline structure inside the flagella

Kinetoplastids

Kinetoplastids have a single large mitochondrion that contains an organized mass of DNA called a kinetoplast

Include species that feed on prokaryotes in freshwater

Euglenids

Has a pocket at one end where flagella emerge

Some are mixotrophs phs

Photosynthesis and Heterotrophic - Phagocytosis

Eyespot

Light detector

Trypanosoma (diease)

Transmitted by tsetse flies in Africa

Causes African sleeping sickness

Constantly changes surface proteins → evades immune defense

Deadly if untreated

Part of the Euglenozoan

Chagas Disease

From the euglenozoan group

Transmitted by bloodsucking insects and can lead to congestive heart failure

Early symptoms include fever, body aches, and eye swelling

“Bait and Switch”

1. They are coated with millions

of copies of a single protein

2. When the host’s immune

system recognizes the

protein to attack

3. New generations of the

parasite switches to another

surface protein with a

different molecular structure

4. These “frequent changes” in

The surface proteins prevent

the host from developing

proper immunity

SAR: Stramenopiles

“Straw hair” in Latin

Numerous fine, hairlike flagella

Paired with a shorter smooth, non-hairy flagellum

Includes some of the most important photosynthetic organisms on the planet

-Diatoms

-Brown Algae

-Oomycetes

Diatoms

Stramenopiles with intricate silica (glass) cell walls

A major component of phytoplankton in oceans and lakes

Photosynthetic → produce 20% of the global oxygen supply

Base of aquatic food webs

Brown Algae: Underwater Forests

Includes the largest protists (multicellular)

Form kelp forestss → biodiversity hotspots

Used in Food industry

Holdfast

A rootlike structure; anchors down algae

Stipe

A stemlike structure

Blades

Leaflike structure

No tissues or organs in any of the three

Sporophytes

diploid individual; produces spores

The spores are haploid and move by flagella

Zoospores divide by mitosis and develop into male and female gametophytes

Part of the brown algae group

Gametophytes

Produces gametes

Hetermorphic

Sporophytes and gametophytes are structurally different

Isomorphic

Structurally the same

Oomycetes

Stramenopiles that look like fungi (filamentous)

Previously classified as one (“egg-fungus”)

Cell walls made of cellulose

Decomposers of plant pathogens

Phytophthora infestans (disease)

Caused the Irish Potato Famine

Millions starved, mass migration, 1840’s

Example of protists shaping human history

Turns the stalks and stems of potato and tomato plants into black slime

Supergorup Alveolates

Characterized by alveoli (membrane-bound sacs just under their plasma membranes)

-Dinoflagellates

-Apicomplexans

-Ciliates

Dinoflagellates

Reinforced by cellulose plates

Have two flagella

One of them causes them to spin as they move through the water

Some produce bioluminescence → glowing beaches

Others cause harmful algal blooms (“red tides”) Kills fish and shellfish poision

Sea Sparkle and Red Tides

Apicomplexans

Alveolates are specialized as parasites

• Almost all are parasites in animals

• Virtually all animal species examined so

far attacked by them

Plasmodium → malaria parasite

• Requires two hosts: humans +

mosquitoes (both asexual and sexual)

Mosquito’s partner in Crime

Ciliates: Tiny Powerhouses

Alveolates covered in rows of cilia

• Example: Paramecium

• Use cilia for movement and feeding

• Ciliary beating – gradual, slow, and

controlled movement of cilia

• “The wave” in the stadium

• Most are predators (of bacteria or other

protists)

• Have two nuclei:

• Macronucleus = daily cell function

• Micronucleus = sexual reproduction

(conjugation)

• Show surprising complexity for

single-celled organisms.