Question

question 9 (10 points)
which organisms have bilateral symmetry, a gastrovascular cavity, no true body
cavity, eyespots, and sex organs? some are parasites.

a) cnidarians

b) roundworms

c) echinoderms

d) sponges

e) mollusks

f) arthropods

g) flatworms

h) chordates

i) annelids

Explanation:

• Cnidarians have radial symmetry, not bilateral.
• Roundworms have a pseudocoelom (a type of body cavity), not just a gastrovascular cavity.
• Echinoderms have radial symmetry as adults.
• Sponges have an asymmetrical or radial - like body plan (cellular - level organization, no true tissues in the same sense as higher animals).
• Mollusks have a coelom (a true body cavity in a more complex form than just a gastrovascular cavity).
• Arthropods have a coelom and a more complex body plan with segmented bodies and jointed appendages.
• Flatworms (Platyhelminthes) have bilateral symmetry, a gastrovascular cavity (incomplete digestive system), no true body cavity (acoelomate), some have eyespots (in free - living forms like planarians), and most are hermaphrodites (have both male and female sex organs). Some flatworms are parasites (e.g., tapeworms, flukes).
• Chordates have a more complex body plan with a notochord (at some stage of development), a dorsal nerve cord, etc.
• Annelids have a coelom and a more complex segmented body plan.

Answer:

G. flatworms