Mollusca

Many animals have soft bodies.

These are called molluscs. They live in the sea. Some live in fresh water. Others live on land.

Most have a shell. A mantle helps make the shell. This mantle also helps them breathe. Many have a strong foot. They use this foot to move.

Some molluscs are very smart. Octopuses and squid are in this group.

The giant squid is very big. It is one of the largest animals without bones.

Some molluscs make pearls. People use shells for many things. Some shells were even used as money.

There are many kinds of molluscs. Snails and slugs are very common. They are a big part of this group.

Molluscs are a huge group of animals. There are about 86,600 known species. This makes them the second largest animal group.

Most molluscs have a soft body made of muscle. They have a part called a mantle. This mantle makes a shell. It also makes a space for breathing.

Many molluscs use a radula to eat. A radula is a tongue with tiny teeth. It helps them scrape food.

Some molluscs are very smart. This group is called cephalopods. It includes squid and octopuses. The giant squid is a very large invertebrate.

Snails and slugs are also common. They belong to a group called gastropods. This group makes up 80% of all known species.

Humans use molluscs for food. People also find pearls inside them. Some shells were even used as money in the past.

Molluscs are a huge group of animals. They are the second largest animal phylum on Earth. Only arthropods have more known species. Scientists recognize about 86,600 living species today. There are also many fossil species from long ago. Some estimates say there are 60,000 to 100,000 fossil types.

Most molluscs share a few special body parts. They have a soft body made of muscle. A part called a mantle covers their upper surface. This mantle makes a shell from proteins and calcium carbonate. The mantle also creates a cavity for breathing. Most molluscs use a radula to eat food. This is a rasping tongue with tiny teeth.

History shows these animals have been around for a long time. Evidence suggests they appeared during the Cambrian period. This was between 541 and 485.4 million years ago. Scientists still debate how they first emerged. They also study how they grew into many forms. This study is called malacology.

These animals are very diverse in size and shape. Gastropods like snails and slugs are the biggest group. They make up 80% of all known species.

Cephalopods include squid and octopuses. These are very smart animals. The giant squid is one of the largest invertebrates. Some molluscs can even be dangerous. The blue-ringed octopus has a fatal bite.

Humans have a long history with molluscs. Many people use them as a food source. They also provide luxury items like pearls.

People once used shells as money. Some molluscs even provided purple dye. However, some can cause health problems. A snail can spread a disease called schistosomiasis. This affects about 200 million people.

Mollusca is a massive phylum of invertebrate animals known as molluscs. These creatures are incredibly diverse in their habitats and body structures. They live in oceans, freshwater, and even on land. Molluscs are the second-largest animal phylum on Earth. Only the arthropods have more recognized living species. Scientists currently recognize about 86,600 living species. There are also between 60,000 and 100,000 known fossil species.

To understand how a mollusc works, scientists often look at a "hypothetical ancestral mollusc." This model describes a basic body plan that many species share. The animal is unsegmented and shows bilateral symmetry. A soft body made of muscle contains the internal organs, called the visceral mass. A thick layer of tissue called the mantle covers the upper surface. This mantle secretes a shell made of proteins, chitin, and calcium carbonate.

The mantle also creates a mantle cavity. This is a large space used for breathing and excretion. The anus, genitals, and kidney-like organs called nephridia all open into this cavity. Most molluscs also use a radula to feed. The radula is a rasping tongue covered in tiny teeth. This tool helps them scrape or tear food. In bivalves, like clams, this radula is absent.

Molluscs are divided into several taxonomic classes. The gastropods, which include snails and slugs, are the most diverse. They account for 80% of all classified molluscan species.

Another important group is the cephalopods. This class includes squids, cuttlefish, and octopuses. Cephalopods are among the most neurologically advanced invertebrates. The giant squid is one of the largest known invertebrate species. Bivalves make up about 14% of the total species.

The history of these animals stretches back millions of years. Evidence shows that gastropods, cephalopods, and bivalves appeared during the Cambrian period. This era lasted from 541 to 485.4 million years ago.

Scientists still debate how they emerged from ancestral groups. They also study how they diversified into so many forms. The scientific study of these animals is called malacology.

Molluscs have a significant impact on human life and history. They are a major food source for people worldwide. For centuries, they have provided luxury goods like pearls and sea silk. Some shells were even used as money in preindustrial societies. However, some species can be dangerous. The blue-ringed octopus has a bite that is often fatal.

Other cone snails produce venoms used in neurological research.

There are also serious health and environmental connections. A disease called schistosomiasis is spread by water snails. This condition affects about 200 million people.

Some snails and slugs are also major agricultural pests. If introduced to new environments, they can damage entire ecosystems. While most molluscs live in the sea, non-marine species are very vulnerable. About 42% of all recorded extinctions since 1500 have been molluscs.