Vertebrate

Some animals have a hard spine.

This spine protects their body. It also keeps them strong.

A hard skull protects the brain.

These animals can be very small. They can also be very large. A blue whale is huge!

Many animals have bones. Fish live in the water. Birds fly in the sky. Some animals live on land.

Some animals have four legs. These animals walk on the ground. This helps them move around. They can find food easily.

There are many kinds of these animals. We see them every day. They are all very special.

Vertebrates are a large group of animals. They have a vertebral column. This is a spine that protects the spinal cord. They also have a cranium. A cranium is a skull that protects the brain.

There are about 65,000 species of vertebrates. This group includes fish, birds, and mammals. It also includes reptiles and amphibians. Some fish have no jaws. Other fish have jaws.

Vertebrates first appeared a long time ago. They lived about 518 million years ago.

Some early fish had fins with bones. These fins changed into legs. This let animals walk on land. These animals are called tetrapods.

Vertebrates come in many sizes. A tiny frog can be very small. A blue whale is very big. It can weigh 150 tonnes.

Most vertebrates live in water. Many others live on land. Many species are now in decline. This is due to changes in the world.

Vertebrates are a huge group of animals. They are part of a larger group called Chordata. There are about 65,000 different species of vertebrates. This group includes many animals you know, like birds and mammals. It also includes reptiles, amphibians, and many types of fish.

Even though they are so successful, they make up less than five percent of all animal species.

What makes a vertebrate special is its body structure. All vertebrates have a vertebral column, which is a spine. This spine protects a delicate nerve cord called the spinal cord. They also have a cranium, which is a skull that protects the brain. Most vertebrates have a large brain divided into three or more parts. They also have a muscular heart with many chambers. Their bodies use sense organs like eyes, ears, and noses to learn about the world.

Vertebrates have a very long history on Earth. The first ones appeared during the Cambrian explosion about 518 million years ago.

Early animals like Haikouichthys had a basic body plan but no jaws. Later, jawed fish appeared during the Ordovician or Silurian periods. Bony fish then appeared in the Silurian and grew in number during the Devonian period.

Eventually, some fish developed limbs to become the first tetrapods.

Many different groups of animals appeared through different ages. During the Triassic, both dinosaurs and mammals first appeared. Later, in the Jurassic, dinosaurs gave rise to birds.

The current era is called the Cenozoic, or the Age of Mammals. This is because mammals became the main animals on land. Vertebrates can be very different in size. A tiny frog can be very small, but a blue whale can weigh 150 tonnes.

It is helpful to think of a vertebrate like a building with a frame. The spine and skull act like the strong beams that hold everything up.

This frame protects the important parts inside, like the brain and spinal cord. Just as a house has pipes for water, vertebrates have a closed circulatory system. A heart pumps blood to carry oxygen through the body. This system helps all vertebrates, from the smallest fish to the largest whale, stay alive.

Vertebrates, also known as craniates, are a diverse subphylum of animals defined by specific anatomical structures. They are characterized by having a vertebral column, which is a spine that surrounds and protects the spinal cord. They also possess a cranium, or skull, to protect the brain. This group is part of the larger phylum Chordata. While vertebrates are incredibly successful, they represent less than five percent of all described animal species. However, they include roughly 65,000 species, making them a massive and important grouping.

The biological mechanism of a vertebrate relies on a complex, integrated body plan. During embryonic development, a layer of cells along the back folds and fuses to form a hollow neural tube. This tube eventually develops into the brain at the front and the spinal cord along the back. In most vertebrates, a structure called a notochord is replaced by a bony or cartilaginous vertebral column. This column provides a strong but flexible skeletal structure. This skeleton supports muscles along the back, allowing for efficient movement, such as swimming.

Vertebrates possess several unique biological systems that distinguish them from other chordates. They have a large brain that is typically divided into three or more sections. Their internal organs include a muscular, multi-chambered heart that drives a closed circulatory system. This system uses blood to transport oxygen from the gills or lungs to the rest of the body. They also feature specialized sense organs, including eyes, ears, and a nose. Their digestive systems are complex, containing a stomach, liver, pancreas, and intestines.

The evolutionary history of vertebrates spans hundreds of millions of years. The first vertebrates emerged during the Cambrian explosion approximately 518 million years ago. Early organisms like Haikouichthys possessed a basic body plan with a notochord and a head, but they lacked jaws.

Jawed vertebrates, known as Gnathostomata, evolved later during the Ordovician or Silurian periods. Bony fishes appeared in the Silurian and underwent massive diversification during the Devonian period. This era is often called the "Age of Fishes."

Significant transitions occurred as vertebrates moved from water to land. Toward the end of the Devonian, a lineage of bony fishes called sarcopterygii developed muscular fins. These fins eventually evolved into two pairs of walking legs, creating the first tetrapods.

These tetrapods established themselves as amphibians on land during the Carboniferous period. Later, during the Triassic, mammals and dinosaurs appeared. In the Jurassic, dinosaurs eventually gave rise to birds. The current Cenozoic era is often called the "Age of Mammals" because they have become the dominant terrestrial group.

Vertebrates exhibit an incredible range of physical scales and sizes. They can be as small as the Brachycephalus pulex frog. Conversely, the blue whale can reach a massive weight of 150 tonnes. This diversity is matched by their variety of habitats, ranging from the deep oceans to dry land. Today, many vertebrate populations are in steep decline. This decline is caused by factors like climate change, pollution, habitat loss, and invasive species.

Taxonomists have long debated how to classify these animals. In 1801, Jean-Baptiste Lamarck identified vertebrates as a distinct group from invertebrates. Later, scientists like Edward Drinker Cope divided them into jawless vertebrates, or Agnatha, and jawed vertebrates, or Gnathostomata. Modern molecular biology has added new layers to this understanding. Scientists have identified five specific molecular markers, or conserved signature indels, that are shared exclusively by all vertebrates. These protein sequences help researchers distinguish the vertebrate subphylum from all other animal groups.