In contrast to annelids the platyhelminthes show
- absence of body cavity
- bilateral symmetry
- radial symmetry
- presence of pseudocoel.
Answer
(1) absence of body cavity
Solution
As per NCERT, the animals in which the body cavity is absent are called acoelomates, e.g. platyhelminthes, whereas annelids are coelomates (true coelom lined by mesoderm).
Both groups are bilaterally symmetrical, so (2) is common to both and (3) fits neither, and pseudocoel is seen in aschelminthes, not in platyhelminthes.
∴ In contrast to annelids, platyhelminthes show absence of body cavity.
Answer: (1)