Question

Which of the following features is not present in Phylum Arthropoda?

• A. Parapodia
• B. Jointed appendages
• C. Chitinous exoskeleton
• D. Metameric segmentation

Answer 1

Answer:

A. Parapodia

• Arthropoda is the largest phylum in the animal kingdom, comprising over 80% of all named animal species.

• The term 'Arthropoda' is derived from the Greek words arthros (joint) and podos (foot), meaning 'jointed appendages.'

• Exoskeleton: They possess a tough, protective exoskeleton made primarily of chitin, which provides structural support and prevents desiccation.

• Segmentation: Their bodies are metamerically segmented, often grouped into distinct regions: head, thorax, and abdomen (or cephalothorax and abdomen).

• Jointed Appendages: These are specialized for various functions such as locomotion, feeding, sensory reception, and defense.

• Circulatory System: They feature an open circulatory system, where blood (hemolymph) flows through body cavities (hemocoel) rather than enclosed vessels.

• Respiration: Breathing occurs via diverse structures depending on the habitat: gills (aquatic), book lungs (e.g., spiders), book gills (e.g., horseshoe crabs), or tracheal systems (insects).

• Sensory Organs: Well-developed sensory structures include compound eyes, simple eyes (ocelli), antennae, and statocysts for balance.

Excretory Systems

• Excretion occurs through specialized structures such as Malpighian tubules (in insects and spiders), green glands or antennary glands (in crustaceans like prawns), and coxal glands.

I