Biology: Phylum Platyhelminthes Overview

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Questions and Answers

What is one of the key innovations associated with Bilateria organisms?

Cephalization (correct)

Radial symmetry

Photosynthesis

Gastrulation

Which symmetry type is NOT appropriate for Bilateria?

Radial symmetry (correct)

Symmetrical

Bilateral symmetry

Asymmetry

Which of the following phyla are included in the Lophotrochozoa group?

Arthropods and nematodes

Chordates and echinoderms

Annelids and molluscs (correct)

Cnidarians and echinoderms

What is a characteristic feature of Metazoa that allows more complex behavior?

Multicellularity Signup and view all the answers

What does the term 'bilateral symmetry' imply about an organism?

It can be divided into two equal halves along one plane. Signup and view all the answers

What type of body cavity do organisms in Phylum Platyhelminthes possess?

Acoelomate Signup and view all the answers

Which characteristic is associated with the bilateral symmetry of organisms?

Presence of a dorsal and ventral side Signup and view all the answers

What type of larvae is specifically associated with organisms in the Lophotrochozoa group?

Trochophore larvae Signup and view all the answers

Which of the following characteristics is indicative of triploblastic organisms?

Presence of three germ layers Signup and view all the answers

In which developmental process is the mouth formed from the blastopore?

Protostomy Signup and view all the answers

Which group includes organisms like molluscs and annelids?

Lophotrochozoa Signup and view all the answers

Which of the following organisms are considered diploblastic?

Cnidarians Signup and view all the answers

Which type of symmetry is commonly observed in advanced animal forms such as chordates and echinoderms?

Bilateral symmetry Signup and view all the answers

What is one key characteristic of the phylum Platyhelminthes?

Lamellate rhabdites Signup and view all the answers

What is the primary role of the osmoregulatory system in Platyhelminthes living in freshwater?

To regulate the amount of water and solutes in their tissues Signup and view all the answers

What type of waste products do Platyhelminthes primarily excrete through diffusion?

Ammonia Signup and view all the answers

Which of the following is a function of lamellate rhabdites in Platyhelminthes?

Locomotion and gas exchange Signup and view all the answers

What type of symmetry do Platyhelminthes exhibit?

Bilateral symmetry Signup and view all the answers

What is the significance of cephalization in Platyhelminthes?

It indicates a more advanced central nervous system. Signup and view all the answers

What structure caps the protonephridia in Platyhelminthes?

Flame cells Signup and view all the answers

What is the secondary role of the protonephridial system in Platyhelminthes?

Excretion of ammonia Signup and view all the answers

What is the primary role of proglottids in the strobila of a tapeworm?

To act as fully reproductive units Signup and view all the answers

What is a common method of reproduction observed in tapeworms?

Self-fertilization Signup and view all the answers

How does a tapeworm like Taenia saginata obtain nutrients?

By absorbing nutrients directly through the tegument Signup and view all the answers

What condition can result from humans becoming intermediate hosts for Taenia solium?

Cysticercosis Signup and view all the answers

Which of the following best describes the role of the definitive host in the life cycle of Taenia saginata?

It is where the adult tapeworm resides and reproduces Signup and view all the answers

What significant damage can cysticerci cause when they infect the human body?

They can cause extensive damage to various organs Signup and view all the answers

What type of reproductive method is considered rare among tapeworms?

Asexual reproduction Signup and view all the answers

In what stage does the shelled larva of Taenia saginata begin its development within the cow?

In the stomach after hatching Signup and view all the answers

What is the main characteristic of the reproductive system in Platyhelminthes?

They possess copulatory organs and are monoecious. Signup and view all the answers

Which of the following classes of Platyhelminthes is known for being endoparasitic?

Class Cestoda Signup and view all the answers

What type of life cycle do Neodermata often exhibit?

Complex with multiple hosts. Signup and view all the answers

How do flatworms in the Grade Turbellaria typically move?

They crawl on substrate using mucus and cilia. Signup and view all the answers

Which structure is NOT commonly found in the epidermis of higher Platyhelminthes?

Cilia Signup and view all the answers

What is a distinguishing feature of Class Cestoda?

They lack a digestive system entirely. Signup and view all the answers

Which type of reproduction is predominant in Grade Turbellaria?

Both sexual and asexual reproduction. Signup and view all the answers

In endoparasites belonging to the class Trematoda, what is the significance of the anterior adhesive organ?

It is used for attachment to the host. Signup and view all the answers

What method of respiration do Platyhelminthes primarily utilize?

Diffusion through body surface. Signup and view all the answers

Which characteristic is TRUE regarding the gut of Platyhelminthes?

They typically have a blind gut or no gut at all. Signup and view all the answers

Which feature distinguishes the nervous system of Platyhelminthes?

Central nervous system with cephalization. Signup and view all the answers

In the life cycle of Clonorchis sinensis, what is the role of the definitive host?

It is where the adult worm reaches sexual maturity. Signup and view all the answers

Which of the following adaptations is NOT found in endoparasitic Platyhelminthes?

Complex respiratory organs. Signup and view all the answers

What common feature is found in all classes of Platyhelminthes?

Lack of skeletal systems. Signup and view all the answers

Study Notes

Phylum Platyhelminthes

Acoelomate: body cavity filled with parenchyma
Muscle cells and parenchyma derived from mesoderm
Triploblastic
Lophotrochozoa
20-30K species
Marine, freshwater, and terrestrial
Many endoparasites

Flatworm Features

Great surface area to volume ratio
Appropriate for gas exchange, nutrition, and waste management
Synapomorphy: lamellate rhabdites, rod-shaped structures that swell when discharged in water to form a mucus coating
Role in locomotion and gas exchange

New features of Flatworms

Excretory/osmoregulatory system
Copulatory organs
Cephalization
Central nervous system

Excretory/Osmoregulatory System

Excretion: elimination of metabolic waste products
Osmoregulation: maintenance of stable internal solutes concentrations, regulation of total amount of solutes in a solution
In sponges and cnidarians, these processes are mainly at the cellular level
Most bilaterally symmetrical animals need a system to collect metabolic waste and/or regulate the amount of water in tissues
Protonephridia: network of tubules capped by flame cells inside and opening outside by a nephridiopore
Protonephridia's primary role: remove excess water, especially in freshwater
Protonephridia's secondary role: excretion of ammonia

Central Nervous System

Cephalization: sensory reception, ocelli and chemoreceptors on the head

Copulation

Direct contact between two individuals to transfer sperm
Internal fertilization

Reproductive System

Platyhelminthes are monoecious

Physiology

Respiratory system: diffusion through body surface
Mucus = humid (terrestrial organisms)
Skeletal system: muscles and parenchyma
Circulatory system: none, surface area optimized for many systems

Four Groups of Flatworms

Turbellaria grade (flatworms)
Class Trematoda (flukes)
Class Cestoda (tapeworms)

Grade Turbellaria (Flatworms)

Mostly free-living scavengers and predators
50-500mm
NOT parasites
Typically creep along substrate using mucus and ventral cilia
Epidermis: formed by rhabdite cells and cilia

Grade Turbellaria, Digestive and Nervous Systems

No anus
Cephalization
Primitive CNS
Sensory reception: ocelli and chemoreceptors on the head

Grade Turbellaria, Reproduction and Life Cycle

Sexual reproduction: monoecious, usually practice cross-fertilization
Asexual reproduction: fission, fragmentation, and regeneration
Simple life cycle with direct development (immature instead of larva)

Clade Neodermata

All endoparasites
Complex life cycles
Requires specific sequences of two or more hosts to complete the lifecycle
Intermediate host: worms are immature, no sexual reproduction, asexual reproduction in some species
Definitive host: worms are mature adults, sexual reproduction

Clade Neodermata, Adaptations

Penetration glands
Hooks
Increased reproductive capacity
Epidermis: NOT ciliated, loss of rhabdites, syncytial tegument

Class Trematoda (Flukes)

Leaf-like form, relatively similar to turbellarians
All endoparasites
Socio-economically devastating parasites
Body design reflects adaptations to parasitism
Life cycle involves both sexual and asexual reproduction
Anterior adhesive organ: suckers and hooks

Class Cestoda (Tapeworms)

All endoparasites, adults infect vertebrates' gut
Syncytial tegument (like trematodes)
Intermediate hosts: vertebrates or invertebrates
Monoecious
Some very large, over 8 meters long
Basic body plan: scolex, attachment device (suckers and hooks), NOT head! Strobila: continuous growth behind scolex, made of many proglottids

Class Cestoda: Proglottids and Digestion

Each proglottid is fully reproductive
Self-fertilization is common
No mouth, no digestive system
How do they feed? tegument

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Description

Explore the fascinating world of Phylum Platyhelminthes, commonly known as flatworms. This quiz covers their unique features, body structure, and the importance of their excretory and osmoregulatory systems. Test your knowledge on their classification, habitats, and adaptations.