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Questions and Answers
Which of the following statements about the nervous system of roundworms is accurate?
What adaptation do roundworms use for detecting chemical stimuli?
What describes the reproductive capability of most trematodes?
In terms of body structure, trematodes are characterized by which of the following features?
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What is the primary method of nutrient expulsion for trematodes?
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Which of the following diseases is NOT caused by nematodes?
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What is the typical life cycle characteristic of most trematodes?
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Which feature distinguishes free-living species of roundworms from parasitic species?
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Which part of the trematode's anatomy is primarily responsible for attachment to the host?
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How do roundworms maintain their developmental process during growth?
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What function do flame cells serve in the excretory system of flukes?
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Which of the following diseases can flukes cause?
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What is the primary method of nutrient absorption in cestodes?
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How do cestodes typically reproduce?
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What anatomical feature do cestodes use for attachment to their host?
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What is one of the preventive measures against diseases caused by flukes?
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In cestodes, what are the individual segments containing reproductive organs called?
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Which of the following best describes the body structure of cestodes?
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How do cestodes develop in their life cycle?
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What role do nerve cords play in the nervous system of flukes?
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Which characteristic is NOT true of helminths?
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What is a common transmission route for hookworms?
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Which of the following helminths are classified as Platyhelminths?
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What type of body symmetry do nematodes exhibit?
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Which of the following factors does NOT influence helminth infection?
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What type of digestive system do nematodes have?
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Which statement about helminth infections is accurate?
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What sets trematodes apart from other helminths?
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Which mode of transmission involves the ingestion of contaminated meat?
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Which characteristic is unique to roundworms compared to flatworms?
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Study Notes
Helminths Overview
- Helminths are parasitic worms, classified into Platyhelminthes (flatworms) and Nematoda (roundworms).
- All helminths are generally larger than 1 mm, with some exceeding 1 m in length.
- They possess well-developed organ systems and engage in active feeding.
- Body structures vary: flatworms are flattened and covered with a plasma membrane, while roundworms are cylindrical and covered with cuticle.
- Helminths can be hermaphroditic or have distinct male and female sexes.
Transmission Routes
- Infections can occur through various routes:
- Ingestion of eggs or larvae (e.g., Ascaris, Echinococcus).
- Larval penetration (e.g., hookworms, schistosomes).
- Bite from vectors (arthropods for filarial worms).
- Consumption of infected meat from intermediate hosts (e.g., Clonorchis in fish).
Influencing Factors for Infection
- Key factors include climate, hygiene, diet, and exposure to vectors.
- Helminth infections are prevalent in underdeveloped countries.
Classification of Helminths
- Helminths are mainly classified into two groups:
- Nematodes (roundworms)
- Platyhelminths (flatworms, including trematodes and cestodes).
Nematodes (Roundworms)
- Characterized by a cylindrical shape and bilateral symmetry.
- Body cavity: pseudocoelom, providing space for body functions.
- Complete digestive system includes a mouth and anus.
- Nervous system features dorsal and ventral nerve cords with chemosensory organs (amphids).
- Found in various habitats, feeding on bacteria, fungi, and other organisms or parasitizing plants and animals.
- Reproduction can be dioecious or hermaphroditic, with internal fertilization and periodic molting of the cuticle.
- Examples of diseases: ascariasis, hookworm infections, filariasis.
Trematodes (Flukes)
- Body is flattened, oval or leaf-like, and acoelomate (no true body cavity).
- Equipped with suckers for attachment; oral sucker aids in feeding, while ventral sucker is for attachment.
- Complete digestive system without an anus; waste is expelled via the mouth.
- Often hermaphroditic, with complex life cycles involving multiple hosts, including larval stages in mollusks and adult stages in vertebrates.
- Excretory system features flame cells, and the nervous system consists of ganglia and nerve cords.
- Associated diseases include schistosomiasis, fascioliasis, and clonorchiasis.
Cestodes (Tapeworms)
- Body features a flattened, ribbon-like shape divided into segments (proglottids) containing reproductive organs.
- Scolex is the attachment organ, lacking a mouth or digestive system; may have suckers or hooks.
- Absorb nutrients directly from the host's intestines through their specialized tegument.
- Reproductive organs are hermaphroditic, and fertilized eggs are released from gravid proglottids.
- Life cycle involves multiple intermediate hosts for larval development and definitive hosts (typically vertebrates) for adults.
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