Question

question 1 (10 points)
which organisms have bilateral symmetry, a complete digestive track, a closed circulatory system, a body cavity, and body segments?

a) sponges

b) arthropods

c) roundworms

d) flatworms

e) chordates

f) cnidarians

g) annelids

h) mollusks
i) echinoderms

Explanation:

• Sponges (a) have asymmetrical body plans and lack a complete digestive tract, closed circulatory system, and body segments.
• Arthropods (b) have an open circulatory system.
• Roundworms (c) lack body segments and have a pseudocoelom (not a true body cavity in the same sense as some others here in terms of development) and no closed circulatory system.
• Flatworms (d) lack a body cavity (acoelomate), a complete digestive tract (in many cases, it has a single opening), and a closed circulatory system.
• Chordates (e) have bilateral symmetry, a complete digestive tract, a closed circulatory system, a body cavity (coelom), but not all chordates have obvious body segments (e.g., adult tunicates lack prominent body - like segmentation).
• Cnidarians (f) have radial symmetry, lack a complete digestive tract (single opening), and lack a closed circulatory system.
• Annelids (g) have bilateral symmetry, a complete digestive tract (mouth to anus), a closed circulatory system (in most annelids like earthworms), a true coelom (body cavity), and are segmented.
• Mollusks (h) have bilateral symmetry (in most cases, some like gastropods have torsion but still have bilateral - like origins), a complete digestive tract, a coelom (reduced in some), but have an open circulatory system (except for cephalopods which have a closed circulatory system, but they lack obvious body segments like annelids).
• Echinoderms (i) have radial symmetry (as adults).

Answer:

g) annelids