Question

select the correct answer.
which phylum includes animals that lack tissues?
a. cnidaria
b. porifera
c. platyhelminthes
d. arthropoda
e. chordata

Explanation:

To determine the correct phylum, we analyze each option:

• Option A (Cnidaria): Cnidarians have true tissues (diploblastic), so they are not the answer.
• Option B (Porifera): Sponges (Porifera) are the only animals that lack true tissues; they have cellular - level organization.
• Option C (Platyhelminthes): Flatworms have tissues and are triploblastic, so this is incorrect.
• Option D (Arthropoda): Arthropods have well - developed tissues and organ systems, so this is wrong.
• Option E (Chordata): Chordates have complex tissues and organ systems, so this is incorrect.

Answer:

B. Porifera