Question

like cnidarians, ctenophores have a decentralized nerve net without a brain, and the body wall is composed of two layers: an outer epidermis and inner gastrodermis, with a gelatinous layer of collenchyme (similar to mesoglea) sandwiched between the two tissue layers. unlike cnidarians, ctenophores have a complete digestive system, consisting of a mouth, pharynx, branching gastrovascular canals, and an anal pore through which undigested material is expelled from the body. most ctenophores are monoecious (hermaphroditic), sperm ducts and oviducts transport sperm and eggs, respectively, from the testes and ovaries to the surrounding seawater where fertilization occurs externally. procedure 1 obtain a preserved specimen of pleurobrachia or other species of comb jelly and place it in a small finger bowl. 2 examine this specimen with the dissecting microscope and locate the following structures depicted in figure 8.18: oral lobes or tentacles (if present), mouth, comb rows, pharynx, and anal pore. in the space provided, sketch your specimen and label the structures listed. check your progress 5.1 list two similarities between cnidarians and ctenophores. 1. 2. 5.2 what characteristics of ctenophores cause zoologists to classify them in a separate phylum from cnidarians?

Explanation:

For 5.1, the text states that both cnidarians and ctenophores have a decentralized nerve net without a brain and their body walls are composed of two - layer structures (outer epidermis and inner gastrodermis with a middle layer). For 5.2, ctenophores have a complete digestive system (mouth, pharynx, branching gastrovascular canals, anal pore) which cnidarians lack.

Answer:

5.1

1. Both have a decentralized nerve net without a brain.
2. Both have a body wall composed of an outer epidermis and inner gastrodermis with a layer in - between.

5.2 Ctenophores have a complete digestive system with a mouth, pharynx, branching gastrovascular canals, and an anal pore, which cnidarians do not have.