Question

Bilateral symmetry, metameric segmentation, coelom and open circulatory system characterize which of the following organisms?

• A. Leech
• B. Mussel
• C. Crab
• D. Sponges

Answer 1

The correct option is C Crab

Leech body can be divided vertically into equal halves in only one plane and hence exhibits bilateral symmetry. They have metameric segmentation where there will be a serial repetition of organs in each segment. They are coelomates but with a closed circulatory system.

Mussel body also exhibits bilateral symmetry and is coelomate. But they are unsegmented with an open circulatory system.

Sponges are animals with a cellular grade of body organisation without any circulatory system. They are asymmetrical, no segmentation and acoelomates.

The bodies of animals such as crabs can be divided vertically into two mirror images. So they are bilaterally symmetrical. They have metameric segmentation in which body organs and appendages are serially repeated in each segment. They are coelomates with an open circulatory system.