Classification of Animals (Vertebrates)

Vertebrates are described as those animal species that have a back bone. They are also said to be the most advanced organism on Earth. Each vertebrate consists of special physical traits of having a spinal cord, vertebrae, and notochords since its counterpart are the invertebrates that do not have those traits present in their biological make- up or structure. Aside from its traits, in a broader sense, it is in fact one of the categories under Kingdom Animalia whom Carl Linnaeus, a famous Swedish botanist, zoologist and physicist proposed under his research of the classification of living things so- called the binomial nomenclature.

There are five categories of vertebrates namely mammals, amphibians, fishes, reptiles and birds. All vertebrates have its distinct characteristics and uniqueness from each other, some being warm-blooded and others being cold- blooded. Under warm-blooded or endothermic animals are the mammals and birds while fishes, reptiles and amphibians are classified under cold- blooded or ectothermic animals.

Mammals

These are the type of animals that familiar to many. It includes animals such as cats, dogs, bats, horses, monkeys, whales and humans. These species are found all over the earth in both warm and cold climates. Two characteristics that distinguish mammals from all other vertebrates are: (1) mammals nourish their young milk produced by their mammary glands; (2) the body covering of mammals is hair. The amount of hair varies from group to group. In whales and porpoises, just a few whiskers are found around the mouth. In many others, the hair is in the form of a thick coat of fur.

Birds

These animals are said to belong to a very successful animal group. Members of this class are found in mostly all types of environments. This includes parrots, toucans, owls and penguins. The single characteristic that distinguishes them from all other animals is the presence of feathers which is also greatly found on their wings which enable a few of them to fly. In addition, another unique characteristic they have is there mouth that is in the form of a horn- covered beak or bill and shaped in a manner which allows them to adapt to their surroundings and to capture food.

Fishes

These are any gill-bearing aquatic vertebrate, usually have tails and paired fins on its back and on its belly that enables it swim. Some of examples of these species are sharks, sting rays, and tilapia.

In addition, there are two kinds of fish – the bony and cartilaginous fishes.

·       Bony fishes are the largest group of fish. It is characterized by their bony skeletons, paired fins, and protective overlapping scales. They are found both in fresh and salt water habits. And they swim in side to side movements, using their fins to maintain balance and control of direction in its movement.

·       Cartilaginous fishes have flexible skeletons made up of cartilage tissue and are also further characterized with a unique characteristic of having the swim bladder or lungs absent and the liver filled with oil, in order to provide buoyancy to the body while swimming.

Reptiles

These are the types of animals that are often cold- blooded because they cannot regulate their own body temperature. Their body temperature depends on the external temperature. It includes crocodiles, alligators, turtles, tortoises, lizards and snakes. These species are often compared to the species of amphibians because of the physical appearance; however there are mainly two differences: (1) the outer skin of reptiles is scaly and their toes of claws, while amphibians have moist, glandular skins, and their toes lack claws, (2) the eggs of reptiles are thick and hard shelled in order for the moisture around the embryo to be kept contained in dry land, while for amphibians they lack a hard outer covering and have to be laid in a damp place.

Amphibians

 These creatures spend part of their lives in water and part on land. Young amphibians breathe through their gills. As they grow, their gills disappear and lungs take their place. They have smooth, moist, and their outer skin has no scales.

There are two major groups of amphibians – the tailed amphibians and the tailless amphibians.

·       The tailed amphibians include salamanders and newts. These animals have long bodies, long tails, and two pairs of short legs. Salamanders feed on fish, snails, insects, worms, and other small salamanders. Some are entirely aquatic, while others live under rocks or logs or in other moist places. They are active only at night.

·       The tailless amphibians include frogs and toads. As adults, they have short, squat bodies and lack tails. Their large, powerful hind legs are modified for jumping.

Toads have dry rough and warty skin. They can live on land, far away from water. They undergo hibernation and during this period they burrow themselves into the ground and their life processes slow down and become inactive.

As for frogs, they have thin, moist skin that is loosely attached to their body. They generally live near ponds, streams and other bodies of water. And during hibernation period they burrow in the mud at the bottom of pools and streams. However the common trait the frog and toad share is that they prey over insects and worms and are mainly surrounded by many predators.