Which of the following characteristics is typical of the phylum Arthropoda?

Step 1: Analyze the question You're asked which feature is typical of Arthropoda, the phylum that includes insects, arachnids, crustaceans, and myriapods (e.g., grasshopper, spider, crab, millipede).

Step 2: Recall the key features of Arthropoda

• Bilateral symmetry
• Segmented body, usually divided into regions (head, thorax, abdomen)
• Jointed appendages (the name means "jointed foot")
• Exoskeleton made of chitin, which is shed during moulting (ecdysis)
• Open circulatory system (haemocoel)
• Compound eyes in many groups

Step 3: Evaluate each option

• A. Radial symmetry: Wrong. This belongs to Cnidaria (e.g., Hydra, jellyfish) and Echinodermata. Arthropods are bilaterally symmetrical.
• B. Closed circulatory system: Wrong. Arthropods have an open circulatory system, where blood (haemolymph) bathes the tissues in a body cavity. Closed systems are found in earthworms (Annelida) and vertebrates.
• C. Endoskeleton made of bones: Wrong. Arthropods have a chitinous exoskeleton. Bony endoskeletons belong to vertebrates.
• D. Presence of a segmented body: Correct. Arthropod bodies are segmented, often fused into regions like the head, thorax, and abdomen.

Step 4: Answer

Tip: Remember Arthropoda as "J.S.E.O": Jointed legs, Segmented body, Exoskeleton, Open circulation. If an option mentions radial symmetry, a closed circulation, or bones, it is almost certainly a distractor for this phylum. Note that segmentation is also found in Annelida, so in exams look for it together with jointed appendages and an exoskeleton.