| Birds have a body plan that shows so many
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| | lungs; thus birds receive a supply of air
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| unusual adaptations (mostly aiding
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| | during both inhalation and exhalation.
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| flight) that birds have earned their own
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| | The gas exchange then takes place in the
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| unique class in the vertebrate phylum.
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| | capillaries. The heart has four chambers
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| The skeleton consists of bones which are
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| | and the right aortic arch gives rise to
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| very light. They have large pneumatic
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| | systemic aorta (unlike in the mammals
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| cavities which connect with the
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| | where the left arch is involved).
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| respiratory system. The skull bones are
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| | Postcava receives blood from the limbs
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| fused and do not show sutures. The orbits
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| | via the renal portal system.
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| are large and separated by a bony septum.
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| | Sound production is achieved using the
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| The spine has cervical, thoracic, lumbar
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| | syrinx, a muscular chamber with several
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| and caudal regions with the number of
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| | tympanic membranes, situated at the lower
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| cervical (neck) vertebrae highly variable
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| | end of the trachea where it bifurcates.
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| and especially flexible, but movement is
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| | The digestive system of the bird is
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| reduced in the anterior thoracic
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| | unique and has a crop for storage and a
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| vertebrae and absent in the later
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| | gizzard for grinding food. Most are
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| vertebrae. The last few are fused with
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| | highly adapted for rapid digestion, an
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| the pelvis to form the synsacrum. The
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| | adaptation to flight. Migratory birds
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| ribs are flattened and sternum is keeled
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| | have the additional ability to reduce
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| for the attachment of flight muscles,
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| | parts of the intestines prior to
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| except in the flightless bird orders. The
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| | migration.
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| forelimbs are modified into the wings.
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| | The nervous system, relative to the
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| Unlike mammals, birds don't urinate.
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| | bird's size, is actually quite large. The
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| Their kidneys extract nitrogenous wastes
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| | most developed part of the brain is the
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| from the bloodstream, but instead of
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| | one that controls the flight related
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| excreting it as urea dissolved in urine
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| | function while the cerebellum coordinates
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| as we do, they excrete it in the form of
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| | movement and the cerebrum controls
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| uric acid. They also excrete creatine
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| | behaviour patterns, navigation, mating
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| rather than creatinine as in mammals.
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| | and nest building. A bird's eyes are
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| Uric acid has a very low solubility in
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| | developed for taking off, spotting
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| water, so it emerges as a white paste.
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| | landmarks, hunting and feeding. Birds
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| This material, as well as the output of
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| | with eyes on the side of their head have
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| the intestines, emerges from the bird's
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| | a wide vision field while birds with eyes
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| cloaca. The cloaca is a multi-purpose
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| | on the front of their heads like owls
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| hole for birds: their wastes come out of
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| | have binocular vision and can measure
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| it, they have sex by putting their
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| | depth.
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| cloacas together, and females lay eggs
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| | Most birds have poor sense of smell
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| out of it.
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| | except in the Kiwis and vultures. The
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| Birds have one of the most complex lung
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| | visual system is highly developed. Water
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| system of all organisms. Air enters the
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| | birds have special flexible lenses,
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| bird and immediately 75% of the air
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| | allowing accommodation for vision in air
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| bypasses the lungs and flows directly
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| | and water. Some species also have dual
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| into a posterior air sac which extends
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| | fovea. Retina has a fan shaped blood
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| from the lungs and connects with air
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| | supply system called the pecten. The ear
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| spaces in the bones and fills them with
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| | lacks external pinnae but is covered by
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| air. When the bird exhales the air from
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| | feathers. The inner ear has a cochlea but
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| the posterior air sac is forced into the
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| | is not spiral as in mammals
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