Classification and characteristics of Superclass: Tetrapoda

March 18, 2018

Tetra-four, podos-feet
Primarily terrestrial, some are secondarily aquatic.
Two pairs of pentadactyl limbs.
Body covered by an exoskeleton of epidermal hair, feathers or scales.
Lungs are main respiratory organs. Amphibian may respire by gills, skin or lungs.
3 or 4 chambered heart present.
They are divided into 4 classes:

Class 2: Amphibia

Amphi-dual; bios-life.
Dual mode of life, can live in water or on land.
First chordates to live out of water.
Occupy intermediate space between the fish and reptiles.
Cold blooded vertebrates with two pairs of limbs, fore limbs are smaller than hind limbs.
Have smooth and moist skin with many glands, scales absent.
Two nostrils connected with the buccal cavity.
Heart is three chambered with two auricles and one ventricle.
RBCs are oval, biconvex and nucleated.
Breathe by buccal cavity, lungs and skin. The tadpole larva respire by gills.
Head and trunk are body parts.
Show hibernation (winter sleep) and aestivation (summer sleep).
Moveable eyelids are present in the eyes. Tympanic membrane is found in some cases.
Endoskeleton is large and bony.
Ten pairs of cranial nerves present in the brain.
Metamorphosis is present which includes tadpole stage.
Examples: Rana (frog), Bufo (toad), Hyla, etc.

Image source: britannica

Class 3: Reptilia

crept- creeping.
Dry, horny scaly skin.
Show creeping movement.
Cold blooded animals, terrestrial or aquatic.
Two pairs of pentadactyl limbs. In snakes and some lizards limbs are secondarily lost.
Heart is imperfectly four or completely four chambered.
Respiration always by lungs.
Twelve pairs of cranial nerves present.
RBC is oval, biconvex and nucleated.
Fertilization is internal. Sexes are separate and shows sexual dimorphism.
Eggs are large with much yolk in leathery or limy shells.
There is no metamorphosis.
Examples: cobra, krait, crocodiles.

Image source: wikipedia

Class 4: Aves (birds)

Streamlined body present to reduce the resistance during flight.
Body is covered with feathers.
Forelimbs modified to wings, covered with feathers.
Hind-limbs are suited for walking and perching.
Show better flight adaptation.
Bones are pneumatic i.e. bones are light, porous with air cavities to reduce the body weight.
Heart is four chambered. RBC is oval, biconvex and nucleated.
Air sacs are present.
Warm blooded animals.
Twelve pairs of cranial nerves present.
Have large eyes and a strong sense of light.
Lungs are compact, attached to ribs.
Lungs have air sacs which help in double respiration.
Oviparous, eggs have large yolk covered with hard horny shell.
Right ovary and right oviducts are disappeared reducing the body weight.
Sexes are separate.
Fertilization is internal.

Examples: Crow, Pigeon, Parrot, etc.

Class 5: Mammalia (mammals)

Highly developed animals with a much advance brain.
Body usually covered with hairs.
Mammary glands are present so called mammals.
Includes diverse group of animals from tiny mice to huge whale.
Viviparous in nature i.e. give birth to young ones except class Prototheria (platypus, spiny ant eater).
Senses of sight, hearing and smell are well developed.
Fore limbs and hind limbs are usually present except cetaceans and sirenians.
Various types of teeth present for cutting, tearing or grinding.
Mammal’s skull is unique, brain is more complex.
The parental care is much highly developed and maximum in human.
Feet with five toes for various purposes.
Can fly, glide, jump, swim, burrow and dive.
Respiration takes place by lungs.
Heart is four chambered: two auricles and two ventricles.
External ear or pinnae is present.
Red blood cells are small, biconvex and nonnucleated except camel.
Muscular diaphragm separates the thoracic cavity with the abdominal cavity.
Twelve pairs of cranial nerves present.
Warm blooded animals.
Sexes are separate, fertilization is internal.
More successful and more dominant animals of today.