Answer:D
Explanation: The pulmonary air sacs of birds only permit a unidirectional flow of air through the lungs. Unidirectional flow means that air is inhale and exhale through one trachea alternatively. This means the bird lungs only receive largely fresh air which has a high oxygen content during inhalation and do not receive fresh during exhalation. While air flow bidirectional in mammals.
approximately 115 days
Human red blood cells (RBC), after differentiating from erythroblasts in the bone marrow, are released into the blood and survive in the circulation for approximately 115 days.
The heat from hotter object goes to the cooler object. when they reach the same temperature the heat flow will stop.
Some bones develop within sheet like layers of connective tissue which are called intramembranous bones whereas the bones that are develop from a model of hyaline cartilage and are called endochondral bones.
<h3>Formation of
intramembranous bones and endochondral bones</h3>
Endochondral ossification involves the replacement of hyaline cartilage with bony tissue which leads to the formation of endochondral bones whereas, intramembranous ossification refers to the replacement of sheet-like connective tissue membranes with bony tissue which results in the formation of intramembranous bones.
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