
Concept explainers
Test Your Understanding
1. Which of the following is not a shared derived character of echinoderms? (a) water vascular system (b) notochord (c) tube feet (d) pentaradial symmetry in adult (e) endoskeleton of calcium carbonate plates and spines

Introduction: Animal phylogeny is the rapidly changing field for biologists. Even if the members of the animal kingdom are incredibly diverse, there are various animals sharing certain features that differentiate them from other organisms of the kingdom. The most highly derived body plan among all animals of the animal kingdom is echinoderm. Echinoderms are the animals that have no terrestrial or freshwater representatives and these animals belong to marine habitat.
Answer to Problem 1TYU
Correct answer: The presence of notochord is not a shared derived character of echinoderms. Hence, the correct answer is option (b).
Explanation of Solution
Reason for the correct answer:
The shared derived characters of echinoderms are as follows:
- Presence of water vascular system.
- Presence of numerous tiny tube feet.
- Presence of endoskeleton, ciliated epidermis, and thin covering.
- The adults of echinoderms exhibit pentaradial symmetry.
The presence of notochord is one of the characters of chordates. Some of the chordates have notochord during some time of their developmental cycle, whereas some chordates have notochord during their whole life time like vertebrates. It is not the shared derived character of echinoderms.
Option (b) is given as “notochord”.
The presence of notochord is not a shared derived character of echinoderms. Hence, the correct answer is option (b).
Reasons for the incorrect answers:
Option (a) is given as “water vascular system”.
The unique structural derived character of echinoderms is the presence of a network of fluid-filled canals and chambers called water vascular system. Hence, option (a) is incorrect.
Option (c) is given as “tube feet”.
The presence of numerous tiny tube feet is one the structural unique character of echinoderms. Hence, option (c) is incorrect.
Option (d) is given as “pentaradial symmetry in adult”.
The echinoderm adult exhibits pentaradial symmetry and the larval form exhibits bilateral symmetry. Hence, option (d) is incorrect.
Option (e) is given as “endoskeleton of calcium carbonate plates and spines”.
The presence of endoskeleton, ciliated epidermis, and thin covering is the unique feature of echinoderm. The endoskeleton of echinoderms consists of calcium carbonate (CaCO3) spines and plates. Hence, option (e) is incorrect.
Hence, options (a), (c), (d), and (e) are incorrect.
The presence of notochord is not a shared derived character of echinoderms.
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