Chapter 13 — Viruses, Viroids, and Prions

What are the three defining characteristics of protozoa?

They are eukaryotic, unicellular, and lack a cell wall.

How do protozoa move?

Usually using cilia, flagella, or pseudopods.

Where are protozoa commonly found?

In moist environments, including ponds, streams, lakes, oceans, moist soil, and decaying organic matter.

What is a trophozoite?

The motile, feeding stage of a protozoan.

What is a cyst?

The resting stage of a protozoan.

What is the usual nutritional method of protozoa?

Most are chemoheterotrophic, obtaining nutrients by consuming bacteria, organic matter, other protozoa, or host tissues.

What are the six major protozoan groups?

Parabasala, Diplomonadida, Euglenozoa, Alveolates, Rhizaria, and Amoebozoa.

What are the characteristics and example of Parabasala?

Lack mitochondria, have flagella, and have one nucleus. Trichomonas vaginalis causes trichomoniasis.

What are the characteristics and example of Diplomonadida?

Lack mitochondria, Golgi bodies, and peroxisomes; have two equal-sized nuclei and multiple flagella. Example: Giardia lamblia.

What are the two groups of Euglenozoa?

Euglenids and kinetoplastids.

What are Euglenids?

Photoautotrophic unicellular organisms with chloroplasts that can photosynthesize and phagocytize; example: Euglena gracilis.

What are Kinetoplastids?

Organisms with a region of mitochondrial DNA called a kinetoplast; Trypanosoma brucei causes African sleeping sickness.

What are Alveolates?

Protozoa that have membrane-bound cavities called alveoli.

What are the three groups of Alveolates?

Ciliates, apicomplexans, and dinoflagellates.

What is an example of a pathogenic ciliate?

Balantidium coli, which can cause balantidiasis, an intestinal infection associated with diarrhea and abdominal pain.

What are Apicomplexans?

Chemoheterotrophic animal pathogens with organelles that allow them to penetrate host cells; Plasmodium vivax is an example that causes malaria.

What are Dinoflagellates?

Unicellular organisms with photosynthetic pigments; some are bioluminescent or produce neurotoxins. Alexandrium tamarense is associated with red tide and paralytic shellfish poisoning.

What are Rhizaria?

Protozoa with threadlike pseudopods; examples include Foraminifera and Radiolaria.

What are Amoebozoa?

Amoebae with lobe-shaped pseudopods and no shells; Naegleria fowleri is an example of a human pathogen.

What are the general characteristics of fungi?

They are chemoheterotrophs, lack chlorophyll, do not photosynthesize, have cell walls typically made of chitin, and are more closely related to animals than plants.

Which drugs are produced by fungi, and what do they do?

Penicillin prevents peptidoglycan cross-linking; lovastatin reduces cholesterol production; cyclosporine is an immunosuppressant used in transplantation.

What are the three fungal nutrient acquisition types?

Saprobes absorb nutrients from dead material; pathogens kill and then consume material; symbionts obtain nutrients through a relationship that benefits both organisms.

What are the three main helminth groups?

Platyhelminths (flatworms), nematodes (roundworms), and annelids (segmented worms).

What distinguishes the three helminth groups?

Platyhelminths have flat bodies and no body cavity; nematodes are roundworms with a body cavity and two openings; annelids are segmented worms with well-developed organ systems and do not cause disease.

What is the difference between mechanical and biological arthropod vectors?

Mechanical vectors passively carry pathogens on their bodies; biological vectors transmit pathogens and serve as a host for part of the pathogen's life cycle.