Examkin

Question

Difficulty: EasyGrowth, Development, and Metamorphosis

Arthropods exhibit a discontinuous, step-like growth curve because their outer body covering cannot expand continuously as internal tissue accumulates. Which structural feature of arthropods necessitates this periodic moulting (ecdysis) process?

  1. A rigid, non-living chitinous exoskeleton that restricts expansionAnswer
  2. B
    The division of the body into fused abdominal segments and tagmata
  3. C
    The presence of jointed thoracic appendages used for locomotion
  4. D
    An open circulatory system supplying hemolymph directly to organs

Answer

A rigid, non-living chitinous exoskeleton that restricts expansion
Arthropods are covered by a hard, non-living exoskeleton made of chitin and proteins. Because this outer layer cannot grow or stretch, the animal must shed its old exoskeleton (ecdysis) at regular developmental intervals to allow its body size to enlarge, producing a characteristic step-like growth curve.

Step-by-Step Solution

1
Identify the primary physical barrier to continuous outward body expansion in arthropods.
The exoskeleton (cuticle) made of chitin is rigid, non-expandable, and non-living.
Because the cuticle cannot stretch once fully hardened, the organism must periodically shed it (ecdysis) to increase in size.
2
Evaluate alternative structural features regarding their role in growth pattern regulation.
Segmentation, jointed appendages, and circulatory organization are anatomical traits, not physical barriers to tissue expansion.
Only the impermeable and inflexible exoskeleton directly causes the intermittent step-like increase in body size.

Key Concept

Discontinuous growth and ecdysis in arthropods due to a rigid exoskeleton
Estimated Time:45s
Rate this question

Topics

Growth, Development, and Metamorphosis

More questions from this topic