diversity eukaryotic

Protozoa (General)

Unicellular eukaryotes; mostly aerobic heterotrophs; lack a cell wall but have a pellicle; reproduce mainly asexually (binary fission).

Cyst

A dormant, protective form used for survival in harsh conditions

Excyst

the process of returning to the active form when conditions are favorable

Schizogony

Multiple nuclear divisions occur before the cell divides, resulting in many daughter cells simultaneously (seen in Plasmodium).

Amoebozoa, Chromalveolata, and Excavata.

Supergroups

Amoebozoa Movement/Feeding

Use pseudopodia ("false feet") for movement and engulf food via phagocytosis into a food vacuole.

Entamoeba histolytica

Protozoan that infects the large intestine, causing amoebic dysentery (bloody diarrhea); forms cysts for transmission.

Naegleria fowleri

"Brain-eating amoeba" found in warm freshwater; causes rapidly fatal Primary Amoebic Meningioencephalitis (PAM); infection route is only through the nose.

Chromalveolata Structures

Often have complex internal membranes (alveoli); may use cilia for movement/feeding (ciliates) or have an apical complex (apicomplexans).

Apicomplexan Lifestyle

Specialized, obligate intracellular parasites with a structure called an apical complex to help invade host cells.

Plasmodium spp.

Apicomplexan that causes malaria; transmitted by the Anopheles mosquito; infects liver cells and then red blood cells.

Ciliates Function

Covered with cilia for movement and feeding; use contractile vacuoles to maintain osmotic balance; mostly free-living (e.g., Paramecium).

Balantidium coli

The only known pathogenic ciliate in humans; causes intestinal illness (balantidiasis); fecal-oral route.

Oomycetes (Water Molds)

Fungus-like organisms that are not true fungi; cell walls made of cellulose (not chitin); can be plant pathogens (e.g., Phytophthora).

Excavata Key Feature

Unicellular eukaryotes known for a characteristic "excavated" feeding groove; have one or more flagella; modified or absent mitochondria.

Giardia lamblia

Excavata that causes giardiasis ("beaver fever"); acquired by ingesting chlorine-resistant cysts in contaminated water; has two nuclei and mitosomes (modified mitochondria).

Trichomonas vaginalis

STD-causing Excavata; causes trichomoniasis; uses flagella and an undulating membrane; has hydrogenosomes (modified mitochondria); no cyst form.

Euglena

Free-living, freshwater Excavata; is mixotrophic (photosynthetic and heterotrophic); features chloroplasts and an eyespot (stigma).

Trypanosoma brucei

Excavata transmitted by the tsetse fly; causes African Sleeping Sickness; uses antigenic variation to evade the immune system.

Helminths (General)

Multicellular parasitic animals (worms); have complex life cycles involving intermediate host (larval stage) and definitive host (adult stage).

Flatworms (Platyhelminths)

Includes Trematodes (flukes) and Cestodes (tapeworms).

Roundworms (Nematodes)

Cylindrical, unsegmented worms with a complete digestive system; usually dioecious (separate sexes).

Cestodes (Tapeworms) Structure

Long, ribbon-like body with a scolex (head with hooks/suckers) and reproductive segments called proglottids; no digestive system.

Taenia solium

Pork tapeworm; ingestion of eggs can lead to cysticercosis (larvae in tissues) or neurocysticercosis (larvae in CNS/brain), which is serious.

Taenia saginata

Beef tapeworm; usually causes a milder intestinal infection; rarely invades tissues.

Flukes (Trematodes) Features

Leaf-shaped, unsegmented; have oral and ventral suckers; most are hermaphroditic (monoecious) except Schistosoma.

Schistosoma spp.

Blood fluke; causes schistosomiasis (bilharzia); transmitted by direct skin penetration by larvae (cercariae) in contaminated freshwater; requires a snail intermediate host.

Fasciola hepatica

Liver fluke; acquired by eating aquatic plants contaminated with encysted larvae.

Ascaris lumbricoides

Large intestinal roundworm; larvae migrate through the lungs; adults can cause intestinal blockage.

Enterobius vermicularis

Pinworm; most common U.S. worm infection (especially in children); causes perianal itching due to the female laying eggs at night.

Necator americanus

Hookworm; transmitted by skin penetration of larvae in contaminated soil (walking barefoot); feeds on host blood, causing anemia.

Trichinella spiralis

Acquired by eating undercooked meat (pork/wild game); larvae encyst in the host's skeletal muscle (trichinosis).

Fungi (General)

Eukaryotic heterotrophs; cell wall made of chitin; cell membrane contains ergosterol (a major antifungal drug target).

Saprozoic Decomposers

Fungi that feed on dead or decaying organic matter by secreting enzymes and absorbing nutrients.

Molds

multicellular, made of filamentous hyphae (mycelium)

yeasts

unicellular and reproduce by budding

Fungal Spores

Fungi produce spores for reproduction and spread, not for survival in harsh conditions (unlike bacterial endospores).

Candida albicans

A yeast that is normal flora in the mouth, gut, and vagina; causes opportunistic infections like oral thrush and vaginal yeast infections.

Aspergillus fumigatus

A mold found in soil/air; inhalation of spores causes Aspergillosis, including invasive disease in immunocompromised patients.

Antifungals

Drugs that target fungal-specific structures like the cell wall component (chitin) or the membrane sterol (ergosterol).

Algae (General)

Diverse group of autotrophic (photosynthetic) eukaryotes; major oxygen producers and base of aquatic food chains.

Harmful Algal Blooms

Caused by certain algae (e.g., dinoflagellates) that produce toxins; responsible for red tides and can cause paralytic shellfish poisoning (PSP) in humans.

Lichens

A symbiotic organism made of a fungus (mycobiont) and a photosynthetic partner (alga or cyanobacterium).

Lichen Role

Fungus provides structure/protection; photosymbiont provides nutrients; act as bioindicators (sensitive to pollution).