Ch. 12 Protozoa

Question 1

protozoa characteristics

Answer 1

• unicellular
• eukaryotic
• inhabit water and soil
• trophozoite= feeding and growing stage; feeds upon bacteria and small particulate nutrients
• some are normal microbiota for animals
• few cause human disease–but the ones they do cause are BAD (malaria)

Question 2

life cycle of protozoa

Answer 2

• protozoa =”first animal”–not animal like
• now classified in same group of kingdoms as algae
• reproduce asexually by fission, budding, or schizogony(multiple divisions of nucleus to make many daughter cells in one cycle)
• some reproduce sexually by conjugation (two parent cells fuse together and share their DNA with each other, then they separate, each fertilized with DNA from both. later they divide and produce daughters with both parent DNA)
• some produce gametes–haploid sex cells. During reproduction, two gametes fuse to form a diploid zygote

Question 3

encystment

Answer 3

-under adverse conditions, some protozoa produce a protective capsule–cyst
permits survival when nutrients, food, moisture, oxygen, temperature are lacking or if exposed to toxic chemicals Also allows parasite species to survive outside of host–host to host transmission
-if cyst is formed in members of phylum Apicomplexa, it is called an oocyst–a reproductive structure in which new cells are produced asexually.

Question 4

protozoa nutrition

Answer 4

• mostly aerobic heterotrophs –though many intestinal protozoa are capable of anaerobic growth
• two chlorophyll containing groups (dinoflagellates and euglenoids) are often studied with algae
• all live in areas with large supplies of water
• some transport food across the plasma membrane, however some have a protective ring called a PELLICLE so they need special structures to take in food.
• ciliates take in food by waving it towards a “mouth” called a CYTOSTOME.
• amebae engulf good by surrounding it with pseudopods and phagocytizing it.
• digestion takes place in membrane enclosed vacuoles
• waste eliminated through plasma membrane or anal pores

Question 5

feeding grooves

Answer 5

• single celled eukaryotes with a feeding groove in the cytoskeleton have been placed in super kingdom of Excavata
• most are spindle shaped and possess flagella
• giardia lamblia/g. intestinalis/g. duodenalis–parasite found in small intestine of humans and mammals. It does not have a mitochondria; it is excreted in feces as a cyst and survives in the environment until ingested by next host–causes Giardiasis
• trichomonas vaginalis parasite also lacks mitochondria. it has an undulating membrane and does not have a cyst sate. Must be transferred from host to host quickly. Found in vagina and male urinary tract. transmitted sexually or from toilets or towels.

Question 6

euglenozoa

Answer 6

• a phylum under excavata
• flagellated cells, disc shaped mitochondria, and absence of sexual reproduction

-EUGLENOIDS are photoautotrophs; they have pellicles, and move via a flagellum at the anterior end; most have a red eyespot; this organelle senses light and directs cell in that direction; some are chemoheterotrophs; can photozynthesize

• HEMOFLAGELLATES (blood parasites)–transmitted by bite of blood feeding insects and found in circulatory systems of bitten hosts; bodies are long and slender with an undulating membrane
  - included genus Trypanosoma; T. brucei causes african sleeping sickness transmitted by tsetse fly; T. cruzi which causes Chagas’ disease from the kissing bug; after entering the bug, trypanosoma multiplies via schizogony. if insect defecates while biting you, it can contaminate wound with trypanosomes

Question 7

Amebae

Answer 7

• move by extending pseudopods
• Entamoeba histolytica–the only pathogenic ameba found in the human intestine. causes dysentery by attaching to plasma membrane via galactose binding lectins and causes cell lysis; E. dispar is non-pathogenic and does not contain lectins
• acanthamoeba can infect the cornea and cause blindness; grow in water/tap water
• Balamuthia–cause of brain abscesses called granulomatous; most often found in immunosuppressed people; free living ameba found in water, NOT transmitted human to human

Question 8

Apicomplexa

Answer 8

• obligate intracellular parasites
• not motile in their mature forms
• have a complex of special organelles at the apexes of their cells that contain enzymes that penetrate the host’s tissues
• they have a complex life cycle that involves transmission between several hosts which can make it difficult to treat.

ex.
- plasmodium vivax–the causative agent of malaria
- babesia microti–transmitted by tick Ixodes scapularis
- toxoplasma gondii–domestic cats–harmful to pregnant women
- cryptosporidium–transmitted through feces of cows, rodents, dogs, and cats
- cyclospora cayetanensi

Question 9

Apicomplexa–Plasmodium

Answer 9

• -the causative agent of malaria
• Plasmodium grows by sexual reproduction in the Anopheles mosquito–forms a sporozoite–mosquito bites human and injects sporozoite—undergoes schizogony in liver cells and produces thousands of progeny called merozoites which infect red blood cells–young trophozoite looks like a ring and enters ring state—red blood cells eventually rupture and release more merozoites and their waste products that cause chills and fever and the merozoites infect new cells and perpetuate the cycle of asexual reproduction–some develop into male or female gametocytes and can be transmitted into another mosquito where they begin their sexual cycle producing more progeny.

definitive host–mosquito that harbors the sexually reproducing stage of plasmodium
intermediate host–human where parasite undergoes asexual reproduction.

Question 10

ciliates

Answer 10

• have cilia arranged in precise rows on cell
• move in unison to propel tell through environment or bring food to mouth
• only ciliate that is a human parasite is Balantidium coli–causes a severe rare dysentery; when host ingests cyst, it enters large intestine where trophozoites are released; they produce proteases and substances that destroy host cells and tissues

Question 11

slime molds

Answer 11

• closely related to amebae and placed in phylum of Amoebozoa
• two taxa; cellular and plasmodial
• cellular slime molds: eukaryotic cells that resemble amebae; live and grow by ingesting fungi and bacteria by phagocytosis; large numbers of ameboid cells aggregate to form a single structure because some individual amebae produce chemical cyclic AMP (cAMP) toward which others migrate
• plasmodial slime molds: mass of protoplasm with many nuclei (multinucleated)–mass called plasmodium; moves as a giant ameba; cytoplasmic streaming– protoplasm changes both speed and direction so that oxygen and nutrients are evenly distributed– plasmodium continues to grow as long as there is enough food and moisture. Where there isn’t enough nutrients, plasmodium breaks into many groups of protoplasm and they form sporangium where spores develop. when conditions improve, the spores germinate and form a multinucleated plasmodium