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Questions and Answers
Polyplacophora mollusks are also known as snails.
Polyplacophora mollusks are also known as snails.
False
Bivalvia mollusks live only in marine habitats.
Bivalvia mollusks live only in marine habitats.
False
Gastropoda mollusks have a single, uncoiled shell.
Gastropoda mollusks have a single, uncoiled shell.
False
Cephalopoda mollusks are the least intelligent and active invertebrates.
Cephalopoda mollusks are the least intelligent and active invertebrates.
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Hyolitha is an extinct class of mollusks.
Hyolitha is an extinct class of mollusks.
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Mollusks are typically hard-bodied animals.
Mollusks are typically hard-bodied animals.
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Mollusks are found in only a few habitats.
Mollusks are found in only a few habitats.
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Study Notes
Polifera: Phylum of Sponges
- Polifera is a phylum of primitive invertebrate animals, commonly known as sponges.
- Sponges are multicellular organisms with a cellular grade of construction, lacking true tissues and organs.
- Their bodies are permeated by canals and chambers through which water flows.
Characteristics of Sponges
- Sponges are filter feeders, obtaining nutrients from the water that passes through their bodies.
- Sponges have four main classes, classified based on the presence or composition of their spicules and spongin, a fibrous protein.
Classes of Sponges
Calcarea (Calcareous Sponges)
- Have spicules made of calcium carbonate, the main component of seashells.
- Typically small and delicate, found in shallow marine waters.
Hexactinellida (Glass Sponges)
- Have a skeletal network of six-pointed spicules made of silica, the main component of glass.
- Found in deep, cold marine waters and can grow to be quite large.
Demospongiae (Demosponges)
- The largest and most diverse class of sponges, containing about 90% of all known sponge species.
- Can have spicules made of silica or spongin, or a combination of both.
- Found in a wide range of habitats, from freshwater to deep sea.
Homoscleromorpha (Encrusting Sponges)
- The rarest and most recently recognized class of sponges, with only about 117 known species.
- Have a simple body structure and lack spicules altogether.
- Found in marine waters, where they encrust on rocks and other hard surfaces.
Mollusca Phylum
- Mollusca is the second-largest phylum of invertebrate animals, after Arthropoda.
- Mollusks have a soft body, typically with a muscular foot for locomotion, a mantle that secretes a calcareous shell, and a visceral mass that contains internal organs.
Habitat and Diversity
- Mollusks can be found in various habitats, from the deepest ocean trenches to the tops of mountains.
- They play a crucial role in the marine ecosystem, including cleaning up the ocean floor and providing food for other animals.
Classes of Mollusks
- There are eight classes of mollusks, with one (Hyolitha) being extinct.
Aplacophora
- Worm-like, shell-less mollusks with a radula (a rasping tongue-like organ for feeding) but no tentacles.
- They live in deep ocean sediments and feed on microscopic organisms.
Monoplacophora
- Mollusks with a single, cap-like shell, thought to be related to an ancient group that gave rise to other mollusks.
- They live in deep ocean hydrothermal vents and cold seeps.
Polyplacophora (Chitons)
- Mollusks with a series of eight overlapping shell plates on their dorsal (back) side.
- They live in shallow marine waters and graze on algae.
Bivalvia (Bivalves)
- Mollusks with two hinged shells, including clams, oysters, mussels, scallops, and other shellfish.
- They live in marine, freshwater, and terrestrial habitats and feed on plankton or by filtering detritus from the water.
Gastropoda (Snails and Slugs)
- Largest and most diverse class of mollusks, including snails, slugs, limpets, sea slugs, and sea butterflies.
- They have a single, coiled shell that they can withdraw into for protection.
- They live in a wide variety of habitats, including marine, freshwater, and terrestrial environments.
Cephalopoda (Intelligent Invertebrates)
- Most intelligent and active invertebrates, including octopuses, squids, cuttlefish, and nautiluses.
- They have a well-developed nervous system and complex sense organs.
- They have no shell or a reduced internal shell and live in marine habitats as predators.
Scaphopoda (Tusk Shells)
- Foot-first burrowers with a long, pointed shell that is open at both ends.
- They live in marine sediments and feed on plankton and other small organisms that drift by.
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Description
Learn about the characteristics and classification of sponges, a type of primitive invertebrate animal. Discover their unique body structure and feeding habits.
