A cell conducts endocytosis by pinocytosis and phagocytosis.
If the inner lining of the air sacs neither thin nor highly vascularized, then it can be inferred that AIR SACS ARE CANNOT BE THE SITES OF GASEOUS EXCHANGE BETWEEN AIR AND BLOOD. Air sacs are generally lined with mucus and surrounded with blood capillaries.
In case of birds, air sacs play an important role in respiratory system.
Question:
<em>What is Darwin’s theory of the origin of species?</em>
Answer:
<em>The theory of evolution by natural selection, first formulated in Darwin's book "On the Origin of Species" in 1859, is the process by which organisms change over time as a result of changes in heritable physical or behavioral traits.</em>
Hope this helps!
it may thats what ive read when i looked it up