Molecular comparisons place nematodes and arthropods in clade Ecdysozoa. What characteristic do they share that is the basis for the name Ecdysozoa?
a. A complete digestive tract
b. Body segmentation
c. Molting of an exoskeleton
d. Bilateral symmetry

Verified step by step guidance

1. Understand the term 'Ecdysozoa': This clade includes organisms that undergo ecdysis, which is the process of molting or shedding their outer covering (exoskeleton) as they grow.
2. Review the characteristics of nematodes and arthropods: Both groups are known to have an external covering. Nematodes have a cuticle, while arthropods have a more rigid exoskeleton.
3. Connect the process of molting to the clade name: The term 'Ecdysozoa' is derived from 'ecdysis,' which refers to the shedding of the exoskeleton or cuticle. This is a defining feature of this clade.
4. Analyze the answer choices: a) A complete digestive tract is not unique to Ecdysozoa, as many other organisms also have this feature. b) Body segmentation is a characteristic of arthropods but not nematodes. c) Molting of an exoskeleton is directly tied to the process of ecdysis, which defines the clade. d) Bilateral symmetry is a common feature in many animal groups, not specific to Ecdysozoa.
5. Select the correct answer: Based on the shared characteristic of molting, the correct answer is c) molting of an exoskeleton.

Key Concepts

Ecdysozoa

Ecdysozoa is a clade of animals characterized by their ability to molt, or shed their exoskeleton. This process, known as ecdysis, allows for growth and development in organisms that have a rigid outer covering. Nematodes (roundworms) and arthropods (insects, crustaceans, etc.) are key members of this group, highlighting the evolutionary significance of molting in adapting to various environments.

Molting

Molting is the biological process through which certain animals, particularly those in the Ecdysozoa clade, periodically shed their exoskeleton or cuticle. This process is crucial for growth, as the rigid exoskeleton does not expand. After molting, the new exoskeleton is initially soft and allows for further growth before hardening, which is essential for the survival and development of these organisms.

Exoskeleton

An exoskeleton is a hard outer structure that provides support and protection to certain animals, including arthropods and some other invertebrates. Unlike an endoskeleton, which is internal, the exoskeleton must be periodically shed through molting to allow for growth. This feature is a defining characteristic of the Ecdysozoa clade, emphasizing the evolutionary adaptations that facilitate survival in diverse habitats.