Sienna made a chart listing different kinds of mollusks. Which headings correctly complete the chart? X: Sea Urchins Y: Gastropods Z: Cephalopods X: Bivalves Y: Cephalopods Z: Gastropods X: Gastropods Y: Cephalopods Z: Bivalves X: Cephalopods Y: Sea Urchins Z: Gastropods

The correct headings to complete the chart for different kinds of mollusks would be: X: Gastropods, Y: Cephalopods, Z: Bivalves.

Extra: Here's a brief explanation of each group:

- Gastropods: This class includes snails, slugs, and whelks. Gastropods are characterized by a single, usually spirally coiled shell into which the animal can retract. Those without shells are known as slugs. They are the largest group of mollusks and can be found in marine, freshwater, and terrestrial environments.

- Cephalopods: This is a class of mollusks that includes squids, octopuses, cuttlefish, and nautiluses. Cephalopods are known for their complex nervous system and remarkable intelligence among invertebrates. They have a prominent head and a set of arms or tentacles that are often equipped with suckers, which they use for feeding and mobility.

- Bivalves: This class encompasses mollusks like clams, oysters, mussels, and scallops. Bivalves have two shells hinged together, which they can open and close. They are mostly sessile (not moving much) and many are filter-feeders, which means they feed by straining suspended matter and food particles from water.

- Sea Urchins: They are actually not mollusks but belong to a group called echinoderms, which also include sea stars (starfish) and sea cucumbers. They are characterized by their spiny globular body and do not fit into any of the mollusk classes.

Understanding these categories is one part of learning about the diversity of life in the phylum Mollusca. Each group has adapted to different ecological niches and developed unique features that allow them to survive and thrive in a variety of environments.