Amphibian

Amphibians live in many places.

They can be frogs or salamanders. Some are even long and look like worms.

Most start their lives in the water. They are small tadpoles with gills.

As they grow, they change. They grow lungs to breathe air.

Many amphibians use their skin to breathe. This helps them live on land.

They must return to water to lay eggs.

Some amphibians are very tiny. One small frog is smaller than a coin. Other ones can grow very large.

These animals are very special. They connect life in water to life on land.

Amphibians are animals that can live in water and on land.

There are about 8,000 known species. Most of these, nearly 90 percent, are frogs.

Amphibians belong to three main groups. The first is Anura, which are frogs and toads. The second is Urodela, which are salamanders. The third is Gymnophiona, which are caecilians.

Caecilians are long and look like worms.

Most amphibians start as water-dwelling larvae. We often call these tadpoles. They use gills to breathe in the water. As they grow, they undergo metamorphosis. This is a way of changing from a water form to an air-breathing adult. Adults use lungs to breathe air.

Many also use their skin to help them breathe.

Some amphibians are very small. A frog from New Guinea is the smallest vertebrate in the world. Other kinds are very large. The South China giant salamander is the largest living one. Long ago, some prehistoric amphibians were even bigger.

Scientists who study amphibians are called batrachologists.

Amphibians are a special group of animals called vertebrates. They belong to a class named Amphibia. The name comes from an Ancient Greek term. It means "both kinds of life." This refers to how they can live in water and on land.

Most amphibians belong to a group called Lissamphibia. This group includes three main orders. The first is Anura, which are frogs and toads. The second is Urodela, which are salamanders. The third is Gymnophiona, which are caecilians.

Scientists who study these animals are called batrachologists. If they study reptiles too, they are called herpetologists.

Many amphibians follow a specific way of growing. Their life cycle usually starts in the water. They begin as larvae, which are often called tadpoles. These young animals use gills to breathe underwater.

As they grow, they go through metamorphosis. This is a big change from a water form to an adult form. Most adults develop lungs to breathe air. Some small frogs and salamanders do not even have lungs. They rely entirely on their skin to breathe instead.

This skin is very thin and can absorb things.

Amphibians have a very long history on Earth. They first evolved during the Devonian period about 370 million years ago. They grew from lobe-finned fish. These fish had fins that looked like limbs.

Some of these fish had primitive lungs to breathe in low oxygen. This helped them move onto dry land. During the Carboniferous and Permian periods, amphibians were very common. They were even at the top of the food chain. Later, early reptiles began to take over the land.

There are many different sizes of amphibians today. There are about 8,000 known species in the world. Nearly 90 percent of these are frogs. The smallest is a frog from New Guinea called Paedophryne amauensis. It is the smallest vertebrate in the world. On the other hand, the South China giant salamander is the largest living amphibian.

In the past, prehistoric amphibians like Mastodonsaurus were even bigger. They could grow up to 6 meters in length.

Amphibians are very important for understanding our planet. Because they have permeable skin, they are ecological indicators. This means scientists watch them to see if a habitat is healthy.

If the water or land is changing, amphibians feel it first. Sadly, many species have seen a dramatic decline in recent decades. This happens all around the globe.

Protecting their homes helps keep these amazing animals safe. They connect the worlds of water and land in a unique way.

Amphibians are a diverse class of vertebrate animals known as Amphibia. The name comes from the Ancient Greek term meaning "both kinds of life." This describes their ability to live in both aquatic and terrestrial environments.

In a broad sense, the group includes many tetrapods. However, it excludes amniotes, which are animals like reptiles, birds, and mammals. All living amphibians belong to a single group called Lissamphibia. This group is defined by having a common ancestor for all modern species.

Most amphibians undergo a complex life cycle involving metamorphosis. This process changes them from an aquatic larval form into an air-breathing adult. Many species begin as larvae, such as tadpoles, which use gills to breathe underwater.

As they mature, they often develop lungs to breathe air on land. Some small terrestrial species, like certain frogs and salamanders, lack lungs entirely. These animals rely on their skin as a secondary respiratory interface to breathe.

Their skin is highly permeable, meaning it can absorb water and gases easily.

Modern amphibians are organized into three distinct orders. The first is Anura, which includes all frogs and toads. They make up nearly 90% of the approximately 8,000 known amphibian species. The second order is Urodela, which contains salamanders and newts. The third order is Gymnophiona, also known as Apoda, which consists of caecilians.

These caecilians are often limbless and live in different habitats. Each order has developed unique adaptations to survive in its specific ecosystem.

The evolutionary history of amphibians began in the Devonian period. This was approximately 370 million years ago. They evolved from tetrapodomorph sarcopterygians, which were lobe-finned fish.

These fish had articulated, limb-like fins and primitive lungs. These features helped them survive in low-oxygen swamps. Over time, their bony fins evolved into true limbs with digits. Their skeletons became stronger to support their weight on land. They also developed a stapes, an ear bone, from a bone used for breathing.

During the Carboniferous and Permian periods, amphibians were ecologically dominant. They occupied many roles currently held by modern crocodiles. Some were massive land predators that ate large insects. However, they were eventually displaced by early reptiles and basal synapsids. The origin of modern Lissamphibia is still a subject of scientific debate. One hypothesis suggests they came from the diverse temnospondyl group. Another theory suggests they emerged from the lepospondyls.

Amphibians exhibit an incredible range of physical sizes. The smallest known vertebrate is a frog from New Guinea called Paedophryne amauensis. It measures only about 7.7 millimeters in length. In contrast, the South China giant salamander is the largest living amphibian.

Prehistoric amphibians were even larger than modern ones. The temnospondyl Mastodonsaurus could reach lengths of up to 6 meters. These massive creatures show how much the group has changed over millions of years.

Because of their permeable skin, amphibians serve as vital ecological indicators. They are very sensitive to changes in their environment. If a habitat becomes polluted or dry, amphibians are often the first to show signs of stress. This sensitivity makes them important for studying habitat health. Unfortunately, many amphibian populations have declined dramatically in recent decades. This global decline highlights the importance of protecting both water and land ecosystems. Scientists who study them are called batrachologists, while those studying both reptiles and amphibians are called herpetologists.