Introduction to Cnidaria

Question 1

What is a hydrostatic skeleton?

Answer 1

• fluid system that permits the extension of muscles through the antagonistic action of opposing muscles
• permits repeated movement

Question 2

what are the 5 requirements for a fluid/hydrostatic skeleton?

Answer 2

1. fluid filled cavity
2. cavity surrounded by flexible membrane
3. fluid volume remains constant
4. temporary attachment to substrate
5. elastic covering or antagonistic muscles

Question 3

What are the differences between longitudinal and circular muscles?

Answer 3

• Longitudinal muscles will contract, shortening the animal
• circular muscles will contract, lengthening the animal

Question 4

What are the 2 defining characteristics of cnidarians?

Answer 4

• they have cnidae
• they have planular larvae (ciliated, mobile stage as larvae)

Question 5

What are Cnidae?

Answer 5

• Cells that contain a specialized organelle only found in Cindarian phylum.
• 3 major categories, neumatocysts are the most common.
• recreated within cnidoblasts
• function as prey capture, defense, etc.

Question 6

Cnidarians have ______ symmetry

Answer 6

RADIAL

Question 7

What level of tissue organization do Cnidarians have?

Answer 7

• Cnidarians are diploblasts, with 2 embryonic germ layers
• the ectoderm embryo develops into the epidermis
• the endoderm embryo develops into the gastrodermis

Question 8

What are the two basic body plans for cnidarians

Answer 8

medusa and polyp

Question 9

What is the mesoglea?

Answer 9

• layer of non-living material within cnidaria that contains amoeboid archaeocytes
• functions as a hydrostatic skeleton

Question 10

In cnidaria, nerves are distributed _______ across the body, with the exception of the ________

Answer 10

In cnidaria, nerves are distributed EVENLY across the body, with the exception of the GANGLIA

Question 11

Cnidaria lack true muscle tissue, instead have……

Answer 11

• contractive extensions of epidermis (circular) and gastrodermis (longitudinal)