<h2> The average height of people in different nations has has increased approximately by 10 centimeters.</h2><h3>It mostly comes down to nutrition and child-rearing styles. </h3><h3>Some scientists believe that the increase in teenage and out-of-wedlock pregnancies in the developed world may be an unanticipated consequence of improved nutrition.</h3>
Tobacco smoking greatly increased over the last hundred or so years, but the old wives' dictum was always that "Smoking will stunt your growth!"
Hope this helped have a good day = ) .
Answer:
Air sacs do not take part in the actual oxygen exchange, but do greatly enhance its efficiency and allow for the high metabolic rates found in birds. This system also keeps the volume of air in the lung nearly constant.
Explanation:
- Air sacs are found as tiny sacs off the larger breathing tubes (tracheae) of insects, as extensions of the lungs in birds, and as end organs in the lungs of certain other vertebrates. They serve to increase respiratory efficiency by providing a large surface area for gas exchange. See also pulmonary alveolus.
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