Lecture 17: Porifera and Cnidaria

Question 1

What does phylum Porifera refer to?

Answer 1

the sponges

Question 2

what are characteristics of porifera?

Answer 2

• lack symmetry
• range in size
• larvae stage is sessile (attached to one spot and don’t move)

Question 3

what is the morphology of Porifera?

Answer 3

• no obvious tissues or organs (no gut, muscles or nerves)
• structural support comes from spicules
• tiny, hard needles or rods
• calcium carbonate or silica
• some sponges have only tough collagen protein networks for support (spongin)

Question 4

what is Mesohyl?

Answer 4

• A gelatinous acellular layer b/w the outer ‘skin’ and the choanocyte layer
• basically the filler that holds all the cells together

Question 5

what is suspension feeding in porifera?

Answer 5

• tiny food particles are engulfed by phagocytosis at base of choanocyte cell
• amoebocytes nudge up and take up food passed on by choanocyte
• amoebocytes then carry the food and nutrients to other cells or use energy to make spicules or other structural material

Question 6

what is the sponges reproduction like?

Answer 6

• mostly hermaphroditic (male and female at the same time)
• they are sequential hermaphrodites meaning they are first one sex and then they change to the other
• do not have ovaries or testes
• eggs are modified from amoebocytes
• sperm are modified from choanocytes
• external or internal fertilization

Question 7

what is the importance of sponges ecology?

Answer 7

• they filter feed which cleans the water
• they have symbiotic mutualisms w/ single celled algae and other organisms
• some are predatory
• they help with pharmaceuticals like antibiotics and anticancer drugs

Question 8

What does phylum cnidaria refer to?

Answer 8

Jelly fish, hydras, sea anemones, and corals

Question 9

what are the characteristics of cnidaria?

Answer 9

• Eumetazoan: they have true tissues
• radial symmetry
• diploblastic: 2 germ layers and no mesoderm/coelom
• organs are collective tissues specialized for different tasks
• many house symbiotic algae

Question 10

what are the 2 basic body forms of cnidaria?

Answer 10

Polyp (sessile form): oral end upwards, attached to a substrate (ex: sea anemone)

Medusa (motile form): oral end downwards, moves freely through the water via hydrostatic skeleton (ex: jelly fish)

Question 11

All cnidarians are _____ and are named for their unique cells called ____. These types of cells…

Answer 11

• predators and their unique cells are called cnidocytes
• each cnidocyte contains very complex end-cellular structure and the most common type is nematocysts which help for catching prey

Question 12

what do Cnidocytes do?

Answer 12

they act as a defence and catch prey

• they do this one something triggers the spine of the cnidocyte by lighting touching the tip of the spine
• they also have a stomach