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.
Muscular activity of its digestive system distorts the body wall should convince you that the organism is acoelomate.
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Explanation:</u></h3>
An animal that does not have body cavity refers to an acoelomate. It is in contrast with the eucoelomates which are the animals that have body cavity. The acoelomate will not have a cavity which is filled with fluid between the digestive tract and the body. Hence there will be a distortion of body wall by the muscular activity of the digestive system.
Some of the examples of acoelomate are Cnidaria,Porifera , Platyhelminthes, Placozoa ,Gnathostomulida.Nemertina and Mesozoa. The presence of pseudocoelom in which the body cavity will not be lined by the mesodermal cells are the Pseudocoelomate.
B Nature selection for traits the allow for increased rates of reproduction and survival over traits that don't, is correct.
A is also correct
The RODS detects shades of grey and are responsible for peripheral vision, while the CONES are responsible for colour vision and seeing fine details.
Rod cells are photoreceptor cells that are located on the retina of the eyes. Rods cells are usually concentrated at the outer edge of the retina and they are use in peripheral vision. Cones on the other hand are photoreceptor cells which are responsible for colour vision and they work best in bright light.
