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.
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,
·
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,
·
Segmented
body.
·
Each
body segment bears a pair of jointed appendage.
·
Possess
a hard chitinous exoskeleton.
·
Live
in water as well as on land.
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.
·
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.
·
Breathing by lungs.
·
Lay eggs covered with a leathery shell.
·
Some of them have legs.
·
Cold blooded.
Aves – (Birds)
·
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,
·
Give
birth to young ones, while the foetus is grown inside the womb.
·
Young
ones feed on breast milk.
·
Four
chamber heart.
·
Warm
blooded.