Phylum Platyhelminthes Class Turbellaria Flashcards

Phylum Platyhelminthes, Class Turbellaria, Genus Planaria

• Phylum Platyhelminthes includes flatworms with soft-bodied characteristics.
• Class Turbellaria encompasses mostly free-living species, primarily found in aquatic environments.
• The genus Planaria is notable for its regenerative abilities and is often studied in biological research.

Key Anatomical Features

• Auricles:

  • Ear-like lobes rich in sensory cells, primarily for smell, not hearing.

• Pharynx:

  • Functions as a throat, can extend through the ventral mouth for feeding.

• Pharyngeal Sheath:

  • Protective structure surrounding the pharynx, providing physical support.

• Gastrovascular Cavity:

  • Serves as the primary digestive tract for nutrient processing.

• Cerebral Ganglia:

  • Clusters of nerve cells located at the anterior end, acting as a rudimentary brain.

• Nerve Cords:

  • Double row of longitudinally connected ganglia, forming the central nervous system.

• Transverse Nerves:

  • Connective structures creating a ladder-like organization within the nervous system.

• Lateral Nerves:

  • Extend outward from nerve cords, contributing to the nervous system's complexity.

• Ocelli:

  • Simple eye spots that detect light and movement, aiding in navigation.

Reproductive Anatomy

• Ovaries:

  • Fertilization occurs as eggs pass down the oviduct to be discharged.

• Oviduct:

  • Transports sperm anteriorly and facilitates posterior fertilization of eggs.

• Yolk Glands:

  • Produce yolk, which nourishes developing eggs.

• Testis:

  • Located throughout the body, responsible for sperm production.

• Vas Deferens:

  • Carries sperm from testes to vesicles for subsequent storage.

• Seminal Vesicle:

  • Simple tubular glands found posterior to the urinary bladder in various male mammals.

• Seminal Receptacle:

  • Structure that receives sperm from a mating partner during reproduction.

Digestive and Excretory Processes

• Undigested Food Elimination:
  • Planarians regurgitate any indigestible remnants from their digestive cavity.

Sexuality and Reproduction

• Monoecious Nature:
  • Planarians possess both male and female reproductive organs, allowing them to engage in self-fertilization or cross-fertilization.

Adaptations and Functionality

• Three-branched Intestine:

  • Enhances nutrient diffusion efficiency; minimizes distance between food source and cells.

• Cilia on Ventral Epidermis:

  • Facilitate movement and locomotion while absent on the dorsal side for streamlined body structure.