animal biology- chapter 7: flatworms

How many germ layers do flatworms have?

Three - they are triploblastic (ectoderm, mesoderm, endoderm).

What type of body cavity do flatworms have?

no true body cavity; space filled with parenchyma.

Which classes in Platyhelminthes are parasitic?

Trematoda (internal flukes)

Cestoda (internal tapeworms)

Monogenea (external flukes)

Which class is non-parasitic?

Turbellaria (e.g., planarians)

What structure is unique to parasitic flatworms (Neodermata)?

Syncytial tegument - a protective outer layer with no individual cells.

What distinguishes parasitic from non-parasitic flatworms?

Parasitic: Syncytial tegument, often lack a digestive tract (e.g., Cestoda)

Free-living: Ciliated epidermis, complete digestive tract, locomotory cilia

What aids locomotion in Turbellaria?

Cilia on the ventral epidermis

Circular, longitudinal, parenchymal muscles

Dual-gland adhesive organs

What are rhabdites?

Rod-shaped vesicles that release mucus for protection and locomotion.

What are the 3 parts of dual-gland adhesive organs?

Viscid cells - secrete glue

Anchor cells - attach the body to the substrate

Releasing cells - dissolve the glue for detachment

What is a tegument?

A syncytial (shared cytoplasm) protective covering in parasitic flatworms, replacing the ciliated epidermis.

What is a teguments function?

Protection from host enzymes, nutrient absorption, and secretion.

What are flame cells part of?

he protonephridium system - used in osmoregulation and excretion.

How do flame cells work?

Flagella beat to create negative pressure

Fluid is drawn through a mesh (weir) into tubules

Fluid is filtered and modified

Excreted via nephridiopores

What are the three types of nervous tissue organization in flatworms?

Subepidermal nerve plexus

Plexus + longitudinal nerve cords

Nerve cords + primitive brain (cerebral ganglion + ring commissures)

What pattern does the nervous system form?

Ladder-type nervous system.

What are the five sensory receptors in flatworms?

Tactile receptors - touch

Chemoreceptors - detect chemicals

Rheoreceptors - sense water currents

Photoreceptors - light (ocelli)

Statocysts - balance and gravity

Where are auricles found and what are they used for?

On the side of the head; used for chemosensation.