Lab 3: Cnidaria/Platyhelminthes Flashcards
Cnidarian Germ Cell Layers
contain both an ectoderm and endoderm germ cell layer
Cnidarians; diploblastic, or triploblastic?
diploblastic (2 germ cell layers)
2 Cnidarian body forms:
polyp & medusa
Polyp:
cylinder like body with mouth pointing up, and tentacles waving above; sessile (stationary)
Medusa:
Jellyfish bowl shape with mouth pointing down, and tentacles hanging
Gastrodermis:
internal tissue layer formed by endoderm
Epidermis:
External tissue layer formed by the ectoderm
Mesoglea:
Non living gelatinous portion between epidermis and gastrodermis
Difference between sponge and cnidarian layers
Sponges have cell layers, Cnidarians have tissue layers
Gastrovascular Cavity
inner cavity forms mouth and anus
Cnidarian Symmetry
Radial
Ends of a Cnidarian
Oral and aboral
Support: Sponge vs. Cnidarian
Spicules provide rigid mineral support; hydrostatic skeleton
Hydrostatic Skeleton
An enclosed cavity with an incompressible volume of water is surrounded by muscles. Compression of muscles change shape of cavity.
Abilities of muscles: 2 abilities, 1 non-ability
Can contract and relax; cannot lengthen
Antagonistic Muscles Systems
Two opposing muscles systems; e.g: circular muscles and longitudinal muscles
Cnidarians: Obtaining food
Nematocysts: sting prey and lure into gastrovascular cavity
Cnidarians: Feeding strategy
Batch feeding
Batch Feeding
because there is only one cavity which serves as a mouth and anus, Cnidarians eat a lot at once, digest it, then expel waste through the same hole. These kind of animals CANNOT continuously feed.
Cnidarians: Gas Exchange
Diffusion across 1 cell thick external and internal layer. Direct respiration with environment via gastrovascular cavity and external water. No special organs.
Cnidarians: Circulation
Cells in direct contact with environment. Cilia will create water currents in gastrovascular cavity.
Cnidarians: Sensory Nervous System
No central system; diffuse net allows partial sensing, and balance, partial light sensors
Cnidarians: Excretion of Waste
Cells can directly expel waste to environment
Zooxanthellae
Single celled marine algae ingested by Cnidarians. Zooxanthellae provide photosynthetic energy, and receive nutrients like nitrogen and phosphorous.
Platyhelminthes: Classes
Flatworms, tapeworms, flukes
Platyhelminthes: Tissues
Ectoderm, endoderm, and MESODERM layer
Mesoderm Layer:
Contains well developed muscle and organ tissue. Living tissue, unlike the Cnidarian mesoglea.
Platyhelminthes: Support and Movement
contains a living hydrostatic tissue called “mesenchyme tissue”.
Platyhelminthes: Nervous system
Ganglia centered anterior, 2 longitudinal nerve cords in a “ladder” shape. Also eyespots.
Platyhelminthes: Waste Management & Concentration control
Nitrogen diffused out of cells as ammonia, fluid enters through “protonephridia” structures that alter concentrations necessary for the body.
Platyhelminthes: Digestion and circulation
Multiple ways, e.g: pharynx tube, one entrance. Gastrovascular cavity highly branched, allowing direct diffusion into cells from water.
Platyhelminthes: Reproduction
Asexually by splitting into 2 parts and regenerating. Hermaphroditic: can produce egg and sperm, but do not fertilize themselves.
