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Difficulty: HardHigher Invertebrates: Annelida, Mollusca, Arthropoda, and Echinodermata

An adult terrestrial arthropod specimen collected from leaf litter possesses a body divided into two main regions (cephalothorax and abdomen), four pairs of jointed walking legs, no antennae, and internal respiratory structures composed of parallel leaf-like vascular plates. Which taxonomic class does this specimen belong to, and what is its primary respiratory organ?

  1. Class Arachnida and book lungsAnswer
  2. B
    Class Insecta and tracheal tubes
  3. C
    Class Crustacea and green glands
  4. D
    Class Chilopoda and book gills

Answer

Class Arachnida and book lungs
The combination of two body divisions (cephalothorax and abdomen), four pairs of jointed legs, complete absence of antennae, and internal book lungs (stacked vascular plates) specifically defines members of the class Arachnida.

Step-by-Step Solution

1
Analyze body divisions and appendages
Two body regions (cephalothorax and abdomen), four pairs of walking legs, and absence of antennae uniquely identify the specimen as belonging to Class Arachnida within Phylum Arthropoda.
Insects have 3 body parts and 3 pairs of legs; crustaceans have 2 pairs of antennae; myriapods have elongated multi-segmented bodies.
2
Identify internal respiratory structure
Parallel leaf-like vascular plates inside internal chambers correspond to book lungs.
Book lungs are adapted for terrestrial gas exchange in arachnids, where air circulates over stacked vascular lamellae.

Key Concept

Diagnostic characteristics and respiratory mechanisms of Arthropod classes
Estimated Time:1m 30s
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Topics

Higher Invertebrates: Annelida, Mollusca, Arthropoda, and Echinodermata

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