RESUMO - Platelmintos

Summary

This video explains the phylum Platyhelminthes, or flatworms, which are characterized by a dorsoventrally flattened body. These animals range from a few millimeters to several meters in length and can be found in marine, freshwater, and moist environments, with many being parasitic. They are triploblastic and acoelomate, exhibiting bilateral symmetry. The video covers their movement, lack of circulatory and respiratory systems, simple excretory system, and ganglionic nervous system. It also explores their reproductive methods, including sexual and asexual reproduction. The phylum is divided into three classes: Trematoda (parasitic), Cestoda (tapeworms), and Turbellaria (mostly free-living).

Takeaways

• 😀 Platyhelminthes, or flatworms, have a flattened body and can range from a few millimeters to several meters in length.
• 😀 These animals can be found in marine, freshwater, damp soils, and as parasites inside other animals.
• 😀 Platyhelminthes are triblastic, having three germ layers: ectoderm, mesoderm, and endoderm.
• 😀 They are acelomates, meaning they lack a coelom and their body cavity is filled with mesodermal tissue.
• 😀 Platyhelminthes have bilateral symmetry, meaning their bodies can be divided into two equal halves.
• 😀 Their movement is powered by muscle contractions or cilia for swimming.
• 😀 They lack circulatory and respiratory systems, relying on diffusion for gas exchange and waste elimination.
• 😀 Their excretory system is simple and consists of protonephridia with ciliated structures.
• 😀 Some species of platyhelminthes have an incomplete digestive system, with a mouth as the only opening.
• 😀 Platyhelminthes can reproduce sexually (hermaphrodites) and asexually through fission (body division and regeneration).
• 😀 There are three main classes of platyhelminthes: Trematoda (flukes), Cestoda (tapeworms), and Turbellaria (mostly free-living species).

Q & A

What are Platyhelminths commonly known as?

Platyhelminths are commonly known as flatworms, characterized by their flat, dorso-ventrally compressed bodies.

What are some of the environments where Platyhelminths can be found?

Platyhelminths can be found in marine environments, freshwater, moist soils, and as parasites within other animals.

What are two common diseases caused by Platyhelminths in humans?

Platyhelminths cause parasitic diseases like schistosomiasis and taeniasis in humans.

What does it mean that Platyhelminths are acoelomate?

Being acoelomate means that Platyhelminths lack a body cavity (coelom), with the space between their ectoderm and endoderm filled by mesodermal tissue.

What is the body symmetry of Platyhelminths?

Platyhelminths have bilateral symmetry, meaning their body can be divided into two equal halves along a single plane.

How do Platyhelminths move?

Platyhelminths move by muscle contractions that allow them to rotate, twist, or swim using cilia in some species.

Do Platyhelminths have a circulatory or respiratory system?

No, Platyhelminths do not have circulatory or respiratory systems. They rely on diffusion for gas exchange and waste elimination through their body surface.

What is the function of protonephridia in Platyhelminths?

Protonephridia in Platyhelminths are part of their excretory system, consisting of tubule networks with ciliated structures that help in waste removal.

How do Platyhelminths reproduce?

Platyhelminths can reproduce both sexually and asexually. Some species, like planarians, can reproduce asexually by fission, while others have sexual reproduction with hermaphroditic systems.

What are the three main classes of Platyhelminths?

The three main classes of Platyhelminths are Trematoda, Cestoda, and Turbellaria.

What is the primary difference between the classes Trematoda, Cestoda, and Turbellaria?

Trematoda and Cestoda are parasitic, with Trematoda including organisms like *Schistosoma mansoni*, and Cestoda including tapeworms. Turbellaria are mostly free-living species, with many marine representatives, like planarians.

How do tapeworms in the class Cestoda reproduce?

Tapeworms have a segmented body made up of proglottids, which contain both male and female reproductive organs, and they often reproduce via cross-fertilization.

What are planarians and how do they move?

Planarians are members of the Turbellaria class, typically small, free-living, and predatory. They move using cilia on their ventral surface.