Indices of animal classification

The main feature that is used to classify animals is the presence or absence of a back bone (Vertebral Column).

The animal which have a vertebral column are Vertebrates, while the animals which do not have a vertebral column are Invertebrates.

                                                                                Invertebrates

Some of the phyla among invertebrates are indicated  below.

1.    Coelenterata ( Cnidaria ) – Diploblastic animals

2.    Annelida – Segmented worms

3.    Mollusca – Soft bodied animals

4.    Arthropoda – Animals with jointed limbs

1.Coelenterata - ( Diploblastic animals)

Hydra, Jelly fish, sea anemone and corals are some organisms which belongs to this phylum. Some of main features of  Coelenterates  are,

·         Soft, cylindrical body.

·         Has a radial symmetry.

·         Diploblastic- body comprises with two layers .

·         Body cavity has only one opening.

·         Live on fresh water, as well as in sea water.

·         Most Coelenterates have a sedentary life style.

2.Annelida – (Segmented worms)

Earth worms, IIeeches and rag worms (nereis) can be cited as some exampals of this phylum.Main features of Annelides can be summarized as follows;

·         Tripoblastic-Body comprises with three layers.

·         The body is externally as well as internally segmented, (Metameric segmentation).

·         Has a bi- lateral symmetry.

·         Posses hard bristles called chaetae.

·         Possess a coelom, which is a fluid containing body cavity.

3. Mollusca – (Soft bodied animals)

Snails, Cuttlefish, Octopus and some organisms that belongs to the phylum mollusca. Some of the main features of these organisms are given bellow,

·         Soft unsegmented body.

·         Live in water as well as on land.

·         Wet slimy body covering.

·         In some mollusks body is covered with a hard body outer shell.

4.Arthropoda –( Animals with jointed limbs)

Arthropodas are considered as the most successful group of animals. This group contain the most of world’s species of organisms. This amount is considered around 75% or more. Some of main features of Arthropodas are mentioned bellow,

·         Possess jointed limbs.

·         Segmented body.

·         Each body segment bears a pair of jointed appendage.

·         Possess a hard chitinous exoskeleton.

·         Live in water as well as on land.

 Vertebrates

Animals who process a vertebral  coloum are known as Invertebrates.  Invertebrates can be classified under five main groups.

1.      Pisces – Fish

2.      Amphibian – Amphibians

3.      Reptilia – reptiles

4.      Aves – Birds

5.      Mammalia - mammals

Pisces –  (Fish)

Some of main of this group are indicated bellow.

·         Streamline body shape.

·         Body coved with scales.

·         Possess gills for breathing.

·         Compound eyes without eye lids.

·         Internal skeleton for the support function of body.

·         Two chamber hart.

·         Cold blooded.

Amphibian – (Amphibians)

According to the evolutionary evidence, amphibians are the pioneer vertebrates who adapted to live on lands as well as in water. They have their birth in water. Some of the main features are indicated bellow.

·         They have limbs for locomotion.

·         Process s soft, moist skin with glands.

·         No scales are found on skin.

·         Gas exchange takes places via lungs, mouth as well moist skin.

·          Three chambered heart.

·         Cold blooded.

Reptilia – (reptiles)

Reptiles were the first group of animals truly adapted to live in the terrestrial environments. Some features of retiles are summarized as bellow.

·         Dry scaly skin without glands.

·         Breathing by lungs.

·         Lay eggs covered with a leathery shell.

·         Some of them have legs.

·         Cold blooded.

Aves – (Birds)

Main features of birds can be summarized as follows.

·         Streamline body shape which helps for flying.

·         Live on land as well as in air.

·         For limbs are modified to wings, perching or swimming.

·         Body covered with feathers.

·         Breathing by lungs.

·         Four chambered heart.

·         Warm bladed

Mammalia – (mammals)

Some of main features of mammals can be cited as follows,

·         Skins covered with hair and bear various glands. (Mammary glands, sweat glands etc.)

·         Give birth to young ones, while the foetus is grown inside the womb.

·         Young ones feed on breast milk.

·         Four chamber heart.

·         Warm blooded.