Biology STAAR (State of Texas Assessments of Academic Readiness) Practice Test

Which characteristic is associated with echinoderms?

1. They have a soft, jelly-like body

2. They move using tiny tube feet and have spiny skin

3. They primarily inhabit terrestrial environments

4. They share a common ancestor with mammals

The correct answer is: They move using tiny tube feet and have spiny skin

Echinoderms are a unique group of marine animals that include creatures such as starfish, sea urchins, and sea cucumbers. A defining characteristic of echinoderms is their ability to move using tiny tube feet, which are part of their water vascular system. This system allows them to exert pressure in their tube feet, facilitating movement, feeding, and even gas exchange. Additionally, echinoderms possess spiny skin, which provides structural support and protection against predators. The spines are usually developed from the underlying endoskeleton, a feature that distinguishes them from other invertebrates. Collectively, these traits contribute to the echinoderm's ability to thrive in various marine environments. The other options do not accurately describe echinoderms. Their bodies are not soft and jelly-like, and they are primarily found in marine environments rather than terrestrial ones. Although they share a distant common ancestry with all animals, including mammals, this connection is not a characteristic feature that defines them specifically. The presence of tube feet and spiny skin is a hallmark of echinoderm physiology and anatomy.