Phylum - Chordata
Class Amphibia
- As the name indicates (Gr., Amphi : dual, bios, life), amphibians can live in aquatic as well as terrestrial habitats.
- Most of them have two pairs of limbs.
- Body is divisible into head and trunk. Tail may be present in some.
- The amphibian skin is moist (without scales). The eyes have eyelids.
A tympanum represents the ear.- Alimentary canal, urinary and reproductive tracts open into a common chamber called cloaca hich opens to the exterior.
- Respiration is by gills, lungs and through skin.
- The heart is threechambered (two auricles and one ventricle).
- These are cold-blooded animals.
- Sexes are separate.
- Fertilisation is external.
- They are oviparous and development is indirect.
Earliest amphibians -
Ichthyostega
- basically a fish with legs
- numerous digits on hands, feet
- tail fin with fibrous rays like a fish
- one of the best transitional series in the fossil record is from fish to amphibian
Modern amphibians
- tend to rely on cutaneous (skin) respiration more than lungs, some without lungs
- most still require water for early life stages and/or reproduction
- have 3-chambered heart with pulmonary veins (two-loop system)
Examples: Bufo (Toad), Rana (Frog), Hyla (Tree frog), Salamandra (Salamander), Ichthyophis (Limbless amphibia).
d.
Class Reptilia
- The class name refers to their creeping or crawling mode of locomotion
- They are mostly terrestrial animals and their body is covered by dry and cornified skin, epidermal scales or scutes.
- They do not have external ear openings.
- Tympanum represents ear.
- Limbs, when present, are two pairs.
- Heart is usually three-chambered, but four-chambered in crocodiles.
- Reptiles are poikilotherms.
- Snakes and lizards shed their scales as skin cast.
- Sexes are separate.
- Fertilisation is internal.
- They are oviparous and development is direct.
Examples: Chelone (Turtle), Testudo (Tortoise), Chameleon (Tree lizard), Calotes (Garden lizard), Crocodilus (Crocodile), Alligator (Alligator). Hemidactylus (Wall lizard), Poisonous snakes – Naja (Cobra), Bangarus (Krait), Vipera (Viper).
e.
Class Aves– birds
- The characteristic features of Aves (birds) are the presence of feathers and most of them can fly except flightless birds (e.g., Ostrich).
- They possess beak.
- The forelimbs are modified into wings.
- The hind limbs generally have scales and are modified for walking, swimming or clasping the tree branches.
- Skin is dry without glands except the oil gland at the base of the tail.
- Endoskeleton is fully ossified (bony) and the long bones are hollow with air cavities (pneumatic).
- The digestive tract of birds has additional chambers, the crop and gizzard.
- Heart is completely fourchambered.
- They are warm-blooded (homoiothermous) animals, i.e., they are able to maintain a constant body temperature.
- Respiration is by lungs. Air sacs connected to lungs supplement respiration.
- Sexes are separate.
- Fertilisation is internal.
- They are oviparous and development is direct.
- feathers – derived scales, made of keratin
- flight skeleton
- bones tend to be hollow (trait shared with some dinosaurs)
- backbone fused – increase stability
- fused collarbones (“wishbone”)
- keeled sternum – increase area for muscle attachment
- have 4-chambered heart with pulmonary veins (2-loop system) – required to be endothermic or “warm- blooded” = increased metabolism for flight
- superefficient respiration – have air sacs that assure that oxygenated air is always going over the lungs
- lay amniotic eggs (like reptiles)
Examples : Corvus (Crow), Columba (Pigeon), Psittacula (Parrot), Struthio (Ostrich), Pavo (Peacock),
Aptenodytes (Penguin), Neophron (Vulture).
f.
Class Mammalia
- hair unique to and defining of mammals
- long filament of mainly dead skin cells filled with keratin
- used for many purposes – sensory, insulation, camouflage, coloration, protection
- mammary glands – milk-producing glands
- have 4-chambered heart with pulmonary veins (2-loop system), allowing them to be endothermic(“warm-blooded”) and homeothermic
- heterodont teeth
- most have a placenta, a specialized organ that serves as an interface between mother and fetus in the womb (each bloodstream kept separate but in close contact; food, water, oxygen, and antibodies given to fetus, while wastes are carried away) .
Principle - High dose X-ray is passed through the body where the body absorbs this radiation and scatter this radiation to all over the body and the remaining x-ray pattern is recorded for later evolution.
Digital Subtraction Angiography (DSA) - DSA is an imaging technique that produces clear views of flowing blood in vessels and indicates the presence of blockages, If any. Angiography is taken of the organ, for example, heart and its major blood vessels and stored on a computer. A second angiograph is taken after a contact agent containing iodine, which is opaque to X-ray, has been injected into the bloodstream. The first image is digitally substrated from the second leaving behind a clear outline of the blood flow to heart, brain or kidneys. 
