Question

question 6 (10 points)
which organisms have bilateral symmetry, a complete digestive track, and no body segments?

a) mollusks

b) annelids

c) flatworms

d) arthropods

e) chordates

f) echinoderms

g) sponges

h) cnidarians

i) roundworms

Explanation:

• Mollusks: Have bilateral symmetry, a complete digestive tract (mouth to anus), and no body segments.
• Annelids: Have bilateral symmetry, a complete digestive tract, but they have body segments (metamerism).
• Flatworms: Have bilateral symmetry but have an incomplete digestive tract (single opening - mouth).
• Arthropods: Have bilateral symmetry, a complete digestive tract, and body segments (tagmatization).
• Chordates: Have bilateral symmetry (in most cases), a complete digestive tract, and in some (like vertebrates) have body - like segmentation (vertebrae, somites in embryos).
• Echinoderms: Have radial symmetry as adults (bilateral symmetry as larvae).
• Sponges: Have asymmetrical or radial symmetry (no definite digestive tract in the traditional sense).
• Cnidarians: Have radial symmetry and an incomplete digestive tract (gastrovascular cavity with single opening).
• Roundworms: Have bilateral symmetry, a complete digestive tract, but also have a type of body - wall structure (pseudocoelom) and are not segmented in the same way as annelids or arthropods. However, mollusks are the best fit as they clearly match all three criteria (bilateral symmetry, complete digestive tract, no body segments) without any ambiguity.

Answer:

A. mollusks