Why do amphibians have backbones

Depending on the type of frog, the tadpoles will remain in their aquatic form for six to twelve weeks. After that time, a process called metamorphosis begins. Microscopic limbs begin to emerge. This occurs in a similar way as that which takes place in mammal embryos, but much later in the growth process.

Initially, tadpoles have tiny teeth they use to eat plants and algae which are plentiful in the rainy season. During metamorphosis, the teeth disappear, allowing tongue muscles to develop.

These are the muscles we see adult frogs use to skillfully catch insects. As the limbs grow, the tail disappears, and a frog-like face forms, the skull transforms from cartilage into bone. At this point, a very small version of a frog is taking shape. Finally, as part of one of the most fascinating stages of metamorphosis, the tadpole turns into what is considered a froglet.

The tadpole gills required to live underwater, make way for lungs, which allow the froglet to live on land. The tail fully disappears and the result is an adult frog. For instance, people and frogs alike, have a heart, lungs, a stomach, a pancreas, a liver, a gallbladder, and intestines. Likewise, human and frog bone structure is quite similar. Human skeletons have four extremities. However, instead of two legs and two arms, as in humans, frogs have four legs. The bone structures are similar in that each extremity contains two sections.

One bone that is closest to the torso, then a sort of bend, or elbow-type joint, and a second part of the extremity further from the torso. Human arms and legs have one larger bone closest to the torso, with two bones at the end of the extremity that run parallel to each other, and work together. The digits of the human and frog hands are similar as well. As we all know, human beings have five fingers and five toes.

The frog has five toes on its hind legs, but generally only four fingers on the front legs. However, only 5 major groups of animals have backbones.

An animal that has a backbone and skeletal system is called a vertebrate. Vertebrates are animals with backbones and skeletal systems. A backbone can also be called a spine, spinal column, or vertebral column.

The individual bones that make up a backbone are called vertebrae. Can you locate the backbone in the model of this toad skeleton?

Insects do not have a backbone or internal skeleton. Instead, they have an exoskeleton which is a hard outer covering that protects their body. The 5 groups of vertebrates animals that have a backbone are fish, amphibians, reptiles, birds, and mammals. To see find out more about the observable features of these sub-groups and to see how they all fit together you can have a look at the relationship 'tree' - or what we like to call The tree of life.

Can you answer these questions? Click on a question to discover the answer. How many living things are there on the planet? What are kingdoms? How do scientists classify living things? How do we divide the animal kingdom?