Lec. 4 Parasites Flashcards
PROTOZOANS, HELMINTHS, ARTHROPODS
- Have a eukaryotic cell structure
- Do not have cell walls (like fungi, algae,and most bacteria have)
- Are heterotrophs – require at least one organic compound made from the environment
•Like all species of living things, have two essential biological functions:
–Survive
–Reproduce
PROTOZOANS
- Unicellular eukaryotic organisms without cell walls
- Most are free-living in the environment; and do not cause disease;
- Only a small number of species cause disease in humans
HOW PROTOZOANS SURVIVE
•Mechanisms to enhance feeding/nutrition
–Have chemoreceptors to sense food sources
–Some have means of locomotion to reach food
–Can diffuse nutrients in and waste proudcts out through the cell membrane
–Some have specialized structures to consume food
–Some have specialized structures for eliminating waste products
LOCOMOTION WITH PSEUDOPODIA
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LOCOMOTION WITH CILIA
Balantidium coli, an intestinal parasite
LOCOMOTION WITH FLAGELLA
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LOCOMOTION WITH AN UNDULATING MEMBRANE
- Undulating membrane is a modifiedflagellum tucked into the cell membrane at different points
- Trypanosoma brucei gambiense in human blood (causes African sleeping sickness)
ADHESIVE DISK (SUCKER) OF GIARDIA LAMBLIA
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SPECIALIZED FEEDING STRUCTURES IN PROTOZOANS
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HOW PROTOZOANS SURVIVE (continued)
•Structures to avoid harm (heat/drying, chemicals, predators)
–Chemoreceptors to sense toxic substances
–Means of locomotion to move away from toxic substances and predators
–Cyst formations to avoid dessication; 2-3 layers of plasma membrane and metabolism in resting state
•Active motile form is called trophozoite
•Nonmotile form is called cyst
TROPHOZOITE AND CYST OF ENTAMOEBA HISTOLYTICA
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TROPHOZOITE AND CYST OF GIARDIA LAMBLIA
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TYPES OF REPRODUCTION IN PROTOZOANS
•Asexual
–New individuals genetically identical to the parent
–There is an increase in the number of individuals
•Sexual –
–New individuals that are genetically different from both of the two parents
–Genetic material has been exchanged or recombined
–There does not necessarily have to be an increase in the number of new individuals
why would it wanna go through cellular reproduction and not increase the number of organisms? To create genetic variation
ASEXUAL REPRODUCTION IN PROTOZOANS
-Binary fission in Trichomonas vaginalis
- Schizogony – multiple nuclear division without cellular division, then sudden cell Division ( Plasmodium species)
- this happens in some strings of malaria and it makes the person so sick that it makes it easier for mosquitoes to bit them
SEXUAL REPRODUCTION IN PROTOZOANS
- Conjugation in ciliates
- Micronuclei undergo meiosisThe two organisms exchange haploidnuclei through a cytoplasmic bridge;Haploid nucleus fuses with the haploid nucleus that remained in the cell.
- mirconucleus is the one that is involved in sexual reproduction
- it undergoes meiosis