Protists

Ryan KeyesAP Biology

Protista

• Kingdom abandoned – Many protists are more similar to animals, plants or fungi

• The term “protist” is still used to describe any eukaryote which is not animal, plant, or fungi

• Protists are more diverse than any other organism

• Diverse because one cell must carry out all of the average functions

Complexity

• Mostly unicellular, though some are colonial or multicellular

• Some photo-autotrophs, some hetertrophic, and some are both

• Some are asexual, while others undergo meiosis

Endosymbiosis

• Key factor in diversity of protists• Mitochondria from alpha proteobacteria• All eukaryotes studied from a certain point

either have mitochondria or had them at some point

Plastids of endo. sym.

• Red and green algae from a photosynthetic cyanobacteria, supported by similar DNA between algae plastids and cyanobacteria

• R & G algae were also taken in and remain in many other protists

Modified mitochondria

• Diplomonads and parabasalids contain remnants of mitochondria

• Remnants aid in digestion, but do not contain electron trans. chain

• Trichomonas Vaginalis – the infection of the vagina resulting from an anaerobic eukaryote resembling bacteria found in the vagina.

Kinetoplastids

• Contains an organelle, kinetoplast, which stores extranuclear DNA

• African sleeping sickness results from kinetoplastids

• Evades immunity by switching surface proteins every generation

• A third of the genome codes for surface proteins

Dinoflagellates

• Flagellated protists which are the foundation of many water based food-chains

• Have blooms, or massive growths, causing red tides

• Tides can be toxic to both fish and humans

Apicomplexans

• Parasites of mammals, forming lethal diseases• Intricate, multi-host life cycles• Malaria falls into this category• Very evasive due to changing of surface

proteins• Must go through Anopheles mosquitoes and

humans to complete cycle

Ciliates

• Protists using cilia to move and eat• Contain macro and micro-nuclei• Macro nuclei split to reproduce, but

micronuclei simply mix, or conjugate, at times when ciliates cross paths

• Reproduction and sharing of genes are completely separate ideas

Brown Algae

• One of the largest and most complex protists• Their color is due to carotenoids in their

plastids

Seaweed

• A collective group of largest marine algae, i.e. brown, red, and green algae

• Complex multi-cellular anatomy• Closely resemble land based plants• Body is known as a thallus, containing the

stem and root systems, which support the photosynthetic leaves branching off

Kelp

• Seaweed inhabiting the deep sea beyond the intertidal zone

• Can grow up to 60 meters in length• All seaweed have alternation of generations