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

What unique feature do mollusks possess for movement?

1. A hard exoskeleton

2. A muscular foot

3. A swim bladder

4. Jointed legs

The correct answer is: A muscular foot

Mollusks are characterized by a unique structure known as a muscular foot, which plays a crucial role in their movement. This foot can take various forms depending on the type of mollusk, allowing for different modes of locomotion. For example, in cephalopods like squids and octopuses, the muscular foot has evolved into tentacles that aid in swimming and grasping objects. In gastropods such as snails and slugs, the foot acts as a ventral surface that helps them glide over surfaces using muscular contractions. The muscular foot enables mollusks to move efficiently through different environments, whether it's crawling on land, burrowing in sand, or propelling through water. This adaptive feature is integral to their survival, as it allows them to escape predators, search for food, and explore their habitats. The other options do not accurately describe the movement mechanism of mollusks. A hard exoskeleton is typical of arthropods and not mollusks. A swim bladder is found in fish to help control buoyancy, and jointed legs are characteristic of insects and other arthropods, not mollusks. Thus, the presence of a muscular foot is what distinguishes mollusks in terms of movement