Animal Kingdom

Animal Kingdom

On the basis of presence of or absence of vertebral column animal kingdom is divided into vertebrate and invertebrate.

Vertebrates: It includes a vast majority of higher animals. The animals that have backbones or vertebral column are called vertebrates

General characteristics of vertebrates’ animals:

·         The vertebrates have vertebral column which supports the body.

·         Brain is enclosed in a brainbox or cranium.

·         They have post anal tail and gill slits.

·         Their heart is present at ventral surface.

·         Circulatory system is of closed type. Blood is red in column due to presence of hemoglobin (Hb).

·         Excretory organs are one pair of kidneys

·         The co-ordination of body activity is under control of nervous system.

On the basis of habit, habitats, and adaptational features, vertebrates can be grouped in two types. They are: Poikilothermic animals (cold-blooded animals) and homoeothermic animals (warm-blooded animals)

Poikilothermic animals (cold-blooded animals)

It includes those animals which can change their body temperature according to their habitat. It means there body temperature is not constant and changes with their environmental temperature. Furthermore, it includes three classes of vertebrates: Amphibians, Pieces, and Reptilians.

Homoeothermic animals (warm-blooded animals)

These include those animals whose body temperature is constant. Furthermore, it includes two classes: Aves and Mammalia.

v  Differences between poikilothermic and homoeothermic.

Poikilothermic animals	Homoeothermic animals
They can change their body temperature.	They can’t change their body temperature.
They may be aquatic or terrestrial.	They may be aerial or terrestrial.
Most of them have gills for respiration.	They have lungs for respiration.
Skin is either naked or covered with water-proof scales. E.g., fish, frog, snake, etc.	Skin is covered with either hair or feathers. E.g., birds, cow, man, etc.

Classification of Vertebrates

1.       Pisces

The pieces are the most primitive and the first vertebrates. They are fully adapted for aquatic mode of life. There are of great importance to man as they are largely used as food.

General Characteristics

·         Their body is long and streamlined.

·         Body is covered with waterproof scales.

·         They have paired fins for locomotion.

·         Respiration takes place by gills. Gills are covered by operculum.

·         They have air bladder or swim bladder called fins which helps to move body while floating.

·         Their heart is two chambered.

·         They lay eggs in water, so they are called oviparous.

·         Fertilization is external.

·         Examples: laveo, katla, hilsa, seahorse etc.

2.       Amphibian

The term amphibian means animals with double-mode life. Amphibians are called the first land vertebrates but they are not fully adapted. They always have to return in water to lay eggs and for early development.

General Characteristics

·         Their body is divisible into head and trunk.

·         Their skin is usually thin, soft, and moist.

·         They have two pairs of pentadactyle limbs.

·         They breathe through gills at their early stage and through skin and lungs at adult stage.

·         They have three-chambered heart.

·         Their tadpole stage is provided with tail.

·         Some amphibians like toad have poisonous glands on the skin.

·         Example: frog, toad, hyla, salamander, etc.

3.       Reptilia

The term reptilian means the animals which crawl on the ground. They are the first vertebrates which are fully adapted to live in dry land. They need not to return to water for breeding.

General Characteristics

·         The reptiles are cold blooded, terrestrial, or aquatic animals.

·         Their body is covered by dry skins with horny scales.

·         Body can be divided into head, neck, trunk, and tail.

·         They have two pairs of pentadactyle limbs with claws (except snake).

·         They breathe through lungs.

·         They lay eggs on land and babies emerge from the eggs. Fertilization is internal.

·         They have generally three-chambered heart (four-chambered in crocodile).

·         Example: wall lizard, garden lizard, snake, crocodile, tortoise, etc.

4.       Aves

The term Aves means Aerial animals. They evolved from reptiles and still show many reptilian characters. Hence, they are sometimes called glorified reptiles. Birds are well adapted to aerial mode of life. But no bird is purely aerial as they come on the land for rest or in search of food.

General Characteristics

·         Body is streamlined and is divided into head, neck, trunk, and tail.

·         Their body is covered with furs and feathers; scales are present in hind legs only.

·         Jaws are modified into beak and bill, without teeth.

·         Limbs are pentadactyle; forelimbs are modified into wings for flying. Their hind limbs are adapted for bipedal locomotion and for piercing, etc.

·         They have lungs for breathing and air sacs for early flight.

·         Heart is four-chambered.

·         Skeleton is light and spongy due to air cavities.

·         They oviparous and fertilization is internal.

·         Example: lophophourous, parrot, crow, duck, penguin, dove, and other birds.

5.       Mammalia

The term mammal means animals, which give birth and feed their babies on milk from the breast. This class chiefly consists of terrestrial animals. Bat is an aerial mammal. Mammals are able to live in various habitats and under severe environmental conditions. They stand on highest position of all the animals.

General Characteristics

·         Body is covered with soft hair.

·         Body is divided into head, neck, trunk, and tail. Tail is absent in some cases.

·         The female has special mammary glands which secrete milk for nourishment of the young.

·         Skin is mostly dry because of sweat, and sebaceous glands are present in the skins.

·         Muscular partition called diaphragm separates the thoracic cavity containing lungs and heart from the abdomen.

·         They have a pair of external ears called pinnae.

·         They have well-developed sense organs and heart is four chambered.

·         Example: Man, Bat, Whale, Horse, Squirrel, dolphin, Cow, Mouse, Cat, Platypus, Kangaroo, elephant etc.