Types flattened and the sternum is keeled

Types of Adaptations:

Adaptation is caused by evolution-a process of gradual change, which makes animals more suited to survive.
Birds, also known as Aves, are a group of endothermic vertebrates , characterized by feathers, toothless beaked jaws, a four-chambered heart, and a strong yet lightweight skeleton.
Since birds have a backbone they are vertebrates.
Birds have only 2 legs. In birds wings have been evolved from the forelimbs of reptiles.
Large chest muscles in flying birds help them move their wings.
The flight muscles of most are red in colour (“dark meat”) because of presence of many fibres containing myoglobin.
Light-coloured muscles (“white meat”) with many fewer fibres.
The feathers probably evolved in birds from reptiles scales (feathers and scales are made of same tough material as your fingernails).
Their ribs are flattened and the sternum is keeled for the attachment of flight muscles except in the flightless bird orders.
Instead of heavy jaws and teeth, they have lightweight beak (of various sizes and shapes).
Birds also have well developed brain that is probably much larger than lizards and comparable, in fact, with those of rodents.
They also have keen eyesight, their brain is connected to sharp eyes.
Birds have streamlined body so as to reduce the air resistance during flying.

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Significance of these Adaptations:
Members of class Aves (birds) have adapted to land and so modified certain features. They needed to compete with the changing environment like quick senses to be aware of dangers on land. The significance of these adaptations is as follows.
Feathers instead of Limbs:
Most prominent and important of the adaptations of class Aves include development of feathers. They served following purposes:
Birds fly and they use feathers for it. And this feature of birds makes them different from other chordates.
The soft and fluffy down feathers of birds help them insulate by trapping air between them hence keeping birds warm in their natural feather jacket.
The display feathers usually found in male help them attract females for mating.
Bristles found in some birds near eye or mouth help them catch insects; help owls to sense nearby objects; and help woodpecker to keep out dust from their nostrils when they drill.
Feathers also help birds have a streamlined body to help them fly through air easily.
Light Bones:
Hollow or porous bones of birds make them light weight so they may glide in air when they fly.
Some of the bones are fused which makes them strong and help birds in flight to carry their weight in the air.
Beaks in birds vary in shape and size depending on the type of bird.
It might help tear meat of their prey, pick little tasty invertebrates from ground or drill through wood.
Feet of birds help them to do certain functions such as:
Grasping their prey.
Dig through sand for food
Swimming e.g. ducks
Climbing e.g. woodpecker
Four Chambered Heart:
4 chambered heart in birds ensure more oxygen transfer to the whole body.
As they need to fly and are warm blooded, they use lots of energy and thus need ample supply of oxygen.

Homology With Other Chordates:

Four chambered heart:
The structure similarities of a four-chambered heart exist between class aves and class mammalia. Both the classes have 2 atriums and 2 ventricles with separation for oxygenated and deoxygenated blood.

The most common thing in all chordates is the homology in their limbs. They are all built from many individual bones. They are all made up of the same basic bone layout: one long bone attached to two other long bones.

All chordates have a post-anal tail at any part of their life. Post-anal tail is an extension of their body that is beyond the anus. Some chordates have it in their embryonic stage only.


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