planaria lab examining a simple invertebrate. classification: kingdom animalia phylum...
TRANSCRIPT
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 “self-
preservation” 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?