Question

1.What is difference between the tissue organization of a sponge and that of other animals?

2.When it comes to tissue organization, what is the difference between Cnidaria and other animals (Eumetazoa)?

3.What is the unique cell type that Hydras have?

4.When you look at cross-sections throughout the body of a flatworm and an earthworm, what is the most obvious difference between the two that you can see?

Answer 1

1. The body of a sponge has cellular level of organisation. Tissues are absent in the body of a sponge. Other animals have tissue level, organ level and organs system level of organisation.

2. Cnidaria are diploblastic animals and have tissues derived from the ectoderm and endoderm whereas other higher eumetazoa have triploblastic body. Triploblastic animals have three germ layers during the embryonic time ectoderm, endoderm and mesoderm.

3. Cindoblasts or nematoblasts are the unique cell type that hydras have. These cells possess the hypnotoxin that can be inserted into the prey during food capturing.

4. Flatworm are acoelomate organisms whereas earthworm is a coelomate. Flatworms don't have the coelom instead the space between the body wall and alimentary canal is occupied with a mesodermal parenchymatous tissue. Earthworm has a coelom or body cavity between the body wall and the alimentary canal. Coelom in earthworm is lined with mesoderm.