Planaria Lab Examining a simple invertebrate Classification Kingdom

Planaria Lab Examining a simple invertebrate

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

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

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

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

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.

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

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

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

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?