1. Planaria Lab Examining a simple invertebrate

2. Classification: Kingdom Animalia Phylum Platyhelminthes (flat worms) – Characteristics of the flatworm phylum: Bilateral symmetry, cephalized Flat, thin, tapered body Made of epithelial, nerve, and muscle tissue, but have very few organs Most are internal parasites

3. 3 Major Classes (within this phylum): Class: Trematoda – Fluke worms Parasitic Liver Blood

4. 3 Major Classes (within this phylum): Class: Cestoda – Tapeworms Intestinal parasites

5. 3 Major Classes (within this phylum): Class: Turbellaria – Planarians Free-living, scavengers Live in ponds, lakes, moist areas etc. Harmless; part of the food chain Hermaphrodites No blood, few organs Oxygen diffuses into cells directly from water

6. The Planarian Very simple flatworm Soft-bodied, easily damaged, but… Their simplicity allows them to easily regenerate new parts!

7. Movement You will notice than the Planarian can twist, turn, and contract (shorten) its body = MUSCLES You may also notice your worm “gliding” across the water. This is because they have CILIA on their ventral surface that “sweep” them along.

8. The Planarian Nervous system: – Photoreceptors: light-sensitive nerve cells – Chemoreceptors: chemical-sensitive nerve cells (taste and smell) – Mechanoreceptors: touch/pressure-sensitive nerve cells – Thermoreceptors: temperature-sensitive nerve cells

9. The Planarian Nervous System – Not very complex – Simple “brain” = GANGLIA – Operate on a basic “self- preservation” response to environmental stimulus – Eyespots – Ladder-shaped nervous system Longitudinal nerves Transverse nerves, latitudinal

10. The Planarian Digestive System – Single opening (mouth) – Pharynx: feeding tube – Three-part, branched intestine Needed for nutrient distribution to all cells Lack blood, no circulation

11. Your Experiment: Are they touch sensitive? Which parts (anterior or posterior) seem most sensitive? Can they sense gravity (up/down)? Do they sense light? If so, do they prefer dark/light? Can they locate food? How? Are they hungry?