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Questions and Answers
How many extant species of protozoa are estimated to exist?
What is the primary characteristic that defines protozoa?
Which group of protozoa is exclusively parasitic?
Which structure is NOT typically involved in the locomotion of protozoa?
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What is the estimated number of parasitic amoebae species?
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What is the main role of the pellicle in some protozoa?
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Which statement accurately describes the cytoplasm of most protozoa?
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What method do amebas primarily use to obtain food?
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Which of the following is a common type of reproduction in protozoa?
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What type of nutrition do protozoa primarily exhibit?
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Study Notes
Protozoa Overview
- Protozoa are classified as a subkingdom within the kingdom Protista.
- Estimated biodiversity includes approximately 32,000 extant species, possibly exceeding 50,000; 34,000 extinct species, notably Foraminifera.
- Living protozoa can be categorized as 21,000 free-living species and 11,000 parasitic species inhabiting various hosts.
Structure
- Protozoa are unicellular eukaryotic organisms, mostly microscopic with few visible to the naked eye.
- Features include a membrane-enclosed nucleus and organelles functioning similarly to higher animals.
- The plasma membrane covers locomotory structures such as pseudopodia, cilia, and flagella.
- Cytoplasm has two differentiated layers: ectoplasm (outer) and endoplasm (inner), containing organelles.
Nutrition
- Protozoa possess holozoic nutrition, requiring organic materials, either particulate or in solution.
- Methods of ingestion:
- Phagocytosis: Engulfing particulate food.
- Pinocytosis: Ingesting fluids through temporary openings.
Reproduction
- Can be asexual (binary fission, schizogony) or sexual, with various life cycle complexities.
- Binary fission divides protozoa into two identical organisms; different methods apply to flagellates and ciliates.
- Sexual reproduction in apicomplexans involves gamete production, fertilization, and development into oocysts.
Life Cycle Stages
- Protozoans transition through various stages, with trophozoite being the active feeding and multiplying stage.
- Additional stages in life cycles can include merozoites, gametocytes, and cysts.
- Cysts have protective walls enabling survival in adverse conditions, with some capable of producing multiple organisms upon excystiation.
Transmission Modes
- Protozoan parasites utilize four primary transmission modes:
- Direct transmission (e.g., sexual contact in Trichomonas spp.)
- Faecal-oral transmission (cysts passed in feces, e.g., Entamoeba histolytica).
- Vector-borne transmission (e.g., Leishmania transmitted by sandflies).
- Predator-prey transmission.
Parasitic Species Examples
- Giardia lamblia: Causes diarrhea; transmitted via fecal contamination, with cysts developing in the intestine.
- Trichomonas: T. hominis is asymptomatic; T. vaginalis is sexually transmitted and may cause vaginitis.
- Leishmania: Transmitted by sandflies, leading to various forms of leishmaniasis.
Key Characteristics of Parasitic Life
- Complex life cycles may require multiple hosts for completion.
- Reproductive potential can lead to significant host populations, hindered by host defenses or mortality.
- Cysts provide stability for survival in the environment, while oocysts facilitate transmission as part of the sexual life cycle.
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Description
This quiz explores the structure, classification, and development of protozoa, emphasizing their role in parasitism. Perfect for students in Veterinary Medicine, it aligns with the study of Zoology and Plant Biology. Test your knowledge on major divisions of life, including Whittaker’s five-kingdom system.
