Phylum Platyhelminthes: Flatworm Overview

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Questions and Answers

The Phylum Platyhelminthes consists of?

Flatworms

Which of the following are characteristics of Phylum Platyhelminthes? (Select all that apply)

Acoelomate (correct)

Triploblastic (correct)

Bilateral symmetry (correct)

Cylindrical body

What does cephalized mean?

Has a head region

Main characteristics of Platyhelminth bauplan?

Nervous system, gut/pharynx/proboscis, hermaphroditic condition, protonephridia, auricles, ocellus Signup and view all the answers

What are cerebral ganglion?

Brain-like nerves; but not a real brain Signup and view all the answers

What are protonephridia?

Excretion simple kidney-like system Signup and view all the answers

The body wall of Platyhelminthes consists of?

Epidermis, basement membrane, mesoderm, gland cells, & rhabdoids Signup and view all the answers

Platyhelminthes bodies are covered in cilia.

True (A) Signup and view all the answers

The nervous system in Platyhelminthes is structured like a ladder.

True (A) Signup and view all the answers

What types of muscles are present in the mesoderm of Platyhelminths?

Circular, diagonal, longitudinal, dorsoventral Signup and view all the answers

Endoderm in Platyhelminths typically has?

Single cell layer, phagocytic cells, enzymatic gland cells, ciliated in some, extracellular digestion Signup and view all the answers

What do nephridiopores do?

Excretes water almost like urine Signup and view all the answers

Nervous system and sense organs of Platyhelminths consist of?

Cerebral ganglion, dorsal nerve cord, ventral nerve cord, ventrolateral nerve cord, ring commissures Signup and view all the answers

Retinular cells can sense what?

Differences in light but can't form images Signup and view all the answers

What are rheoreceptors?

Sense mechanical cues Signup and view all the answers

What do chemoreceptors sense?

Chemical cues Signup and view all the answers

Class Turbellaria is characterized by?

Predominately free-living & aquatic, epidermis cellular & typically ciliated Signup and view all the answers

Order Acoela under Class Turbellaria has?

No permanent gut cavity, single pharynx, generally small, inhabit marine & brackish water sediments, and have some planktonic forms Signup and view all the answers

Order Polycladida is known for?

Plicate pharynx (proboscis), multi-branched gut, mostly marine Signup and view all the answers

Class Cestoda is commonly referred to as?

Highly modified 'ribbon tapeworm' Signup and view all the answers

Class Cestoda characteristics include?

All endoparasitic, digestive tract absent, anterior scolex Signup and view all the answers

What does hermaphroditic condition mean?

Has both testes and ova Signup and view all the answers

Class Monogenea is characterized by?

Ectoparasitic, life cycle in one host (monogena), anterior prohaptor, posterior opisthaptor Signup and view all the answers

What is the life cycle of Trematodes?

Egg, miracidium, sporocyst, & redia= snail; cercaria= crab; metacercaria & adult= human (final host) Signup and view all the answers

Schistosoma mansoni is known to cause?

Schistomiasis Signup and view all the answers

Schistosomiasis can cause?

Diarrhea, abdominal pain, liver damage, & poor growth Signup and view all the answers

What does Class Cestoda include?

Taenia saginata (beef tapeworm) Signup and view all the answers

Taenia saginata are passed through?

Proglottids (water via feces), zygote (onchospheres) & cysticercus (cow), tapeworm adult (human) Signup and view all the answers

Study Notes

Phylum Platyhelminthes Overview

Comprised of flatworms, known for their flattened body shape.

Characteristics of Platyhelminthes

Triploblastic: three germ layers (ectoderm, mesoderm, endoderm).
Acoelomate: lack a body cavity.
Exhibits spiral cleavage during embryonic development.
Contains a sac-like gut for digestion.
Cephalization present, with a distinct head region.
Displays bilateral symmetry, flattened dorsoventrally.
Protonephridia function as a primitive excretory system.
Includes both parasitic and free-living species.
Primarily hermaphroditic, possessing both male and female reproductive structures.

Structural Features

Cerebral ganglion serves as a simple neural aggregation, functioning like a brain.
Protonephridia function in excretion, resembling a basic kidney system.
Body wall consists of epidermis, basement membrane, mesoderm, gland cells, and rhabdoids, providing structure and function.
Bodies are covered with cilia aiding in locomotion and feeding.
Nervous system designed like a ladder, also includes nerve cords and ganglia.

Mesoderm and Endoderm

Mesoderm in Platyhelminths includes circular, diagonal, longitudinal, and dorsoventral muscle fibers aiding movement.
Endodermal structure features a single cell layer, phagocytic cells, enzymatic glands, and can exhibit extracellular digestion.

Nephridiopores

Structures that excrete waste water, functioning similarly to urine in higher organisms.

Sensory Organs

Retinular cells detect light intensity, though they do not form images.
Rheoreceptors sense mechanical stimuli in the environment.
Chemoreceptors detect chemical signals, aiding in food detection and predator avoidance.

Classifications within Phylum Platyhelminthes

Class Turbellaria:
- Primarily free-living aquatic organisms with a ciliated epidermis.
- Includes taxa such as Order Acoela (no permanent digestive cavity) and Order Polycladida (branched gut).
Class Monogenea:
- Ectoparasitic organisms with a life cycle in one host, featuring specialized attachment structures.
Class Trematoda:
- Endoparasitic species with complex life cycles involving multiple hosts.
- Notable examples include Paragonimus westermani (Japanese lung fluke) and Schistosoma mansoni, which causes schistosomiasis.
Class Cestoda:
- Known for flat, ribbon-like form and absence of a digestive system, with the anterior scolex for attachment.
- Includes Taenia saginata (beef tapeworm), transmitted through proglottids in feces.

Health Implications

Schistosomiasis causes severe outcomes such as diarrhea, abdominal pain, liver damage, and impaired growth due to infection from schistosome species.
Hosts for schistosomes include snails with a skin-penetrating free-living stage.

Reproduction

Hermaphroditic condition allows for both male and female gamete production, enhancing reproductive success in various environments.

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Description

This quiz provides flashcards covering essential aspects of the Phylum Platyhelminthes, commonly known as flatworms. Explore their characteristics, structure, and classification. Ideal for students studying invertebrate zoology or related fields.