Question

The _____are mollusks with a hinged shell. a. bivalves c. gastropods b. barnacles d. cephalopods

Short answer

The answer is a. Bivalves.

Step-by-step solution

Identify definitions

Let's first define what each of the provided options are: a. Bivalves are mollusks that have a body enclosed by a hinged shell consisting of two parts (valves). c. Gastropods are mollusks that often have a single, spiraled shell, like snails. b. Barnacles are crustaceans and do not have a hinged shell like bivalves. d. Cephalopods are mollusks but include creatures like octopuses and squids, which do not have external shells.

Recognize distinguishing features

The key feature to focus on is the 'hinged shell.' Bivalves are the only group mentioned in the options that have a hinged shell. The shell structure of bivalves allows it to open and close at a hinge, which is not a characteristic of the other groups.

Cross-verify with characteristics

Verify from the definitions whether any other options also fit the description. Gastropods can have shells but not hinged ones. Barnacles have hard plates, not a hinged shell. Cephalopods do not have hinged shells but instead may have internal shells or none.

Select the correct answer

From the examination of definitions and characteristics, option a, bivalves, clearly stands out as the correct choice because bivalves specifically have a hinged shell that the other options do not feature.

Key concepts

Mollusks

Mollusks are a diverse group of invertebrates that belong to the phylum Mollusca. They are known for their soft, unsegmented bodies. This group includes creatures such as snails, clams, and octopuses. Mollusks are one of the largest groups of marine animals, but they also inhabit freshwater and terrestrial environments.
The anatomy of mollusks can vary considerably among the different classes, which include gastropods, bivalves, and cephalopods, among others. However, most mollusks share some common features:

• A muscular foot, which is used for locomotion or anchoring themselves to surfaces.
• A mantle, which is a significant part of their anatomy that can secrete calcium carbonate to form a shell in many species.
• A radula, which is a toothed structure used for feeding, although this is absent in some mollusks like bivalves.

The diversity within mollusks is remarkable, with each class adapting unique features to thrive in various environments.

Hinged Shell

The hinged shell is a defining characteristic of bivalves, a class of mollusks that include clams, oysters, and mussels. Bivalves get their name from their two-part shell, which is hinged at the top. This hinge allows the shells to open and close efficiently.
Each shell half is called a valve. These valves are connected at the dorsal end by a flexible ligament, which holds the shells together and allows them to open slightly for feeding or to close tightly for protection.

• Hinged shells serve multiple purposes for bivalves:
• Protection against predators by closing tightly.
• Enable filter feeding by opening slightly to let water flow through gills, capturing food particles.
• Provide structural support to the soft body parts inside.

Being equipped with a hinged shell gives bivalves an advantage in diverse habitats, allowing them to thrive in various marine and freshwater environments.

Marine Biology

Marine biology is the study of organisms that live in the ocean and other saltwater environments. It encompasses a broad range of life forms, from microscopic plankton to massive whales.
Marine biology is crucial because it helps scientists understand the ecological roles of various species and the importance of biodiversity in marine ecosystems. Mollusks, especially bivalves, play a significant role in marine biology for several reasons:

• They are essential in filtering water, which helps maintain water quality and clarity.
• They serve as a food source for many marine animals, including humans.
• Some bivalves contribute to the formation of natural reefs, which provide habitat for other sea life.

Studies in marine biology also focus on the impact of human activities, such as pollution and overfishing, on marine life and ecosystems. Understanding these impacts is vital for developing conservation efforts to protect oceanic environments.

Invertebrate Zoology

Invertebrate zoology is the branch of zoology that focuses on animals without backbones, accounting for approximately 97% of all animal species. This includes vast groups such as mollusks, insects, arachnids, and crustaceans.
Mollusks are a particularly interesting subject within invertebrate zoology due to their diverse range and complex behaviors. Bivalves, being invertebrates, offer unique study opportunities because of their distinct hinged shells and ecological roles.

• Important aspects of studying invertebrate zoology include:
• Understanding anatomical differences and common features among invertebrates.
• Exploring the adaptation mechanisms that allow invertebrates to inhabit various environments.
• Analyzing reproductive strategies and development stages unique to invertebrates.

Knowledge gained from invertebrate zoology contributes to broader ecological studies and helps in understanding evolutionary processes across species.