One possible reason that there are not any really large insects currently living on Earth is that
A)gas exchange across their moist skin surfaces cannot support the metabolic needs of a large body.
B)their lungs never evolved to be as highly branched as a mammal's.
C)their gills do not have as many lamellae as fish gills.
D)the bulk flow of air through their tracheal tubes would be more difficult the larger the body and longer the tracheal tubes.
E)they do not have as many papulae as echinoderms.

Question

Quizplus · Accepted Answer

The bulk flow of air through the tracheal tubes of insects is passive and relies on the diffusion of gases. As the body size of an insect increases, the distance that oxygen needs to diffuse through the tracheal tubes also increases, leading to a decrease in oxygen supply to tissues. This limits the maximum size that insects can attain. Therefore, the correct answer is D - the bulk flow of air through their tracheal tubes would be more difficult the larger the body and longer the tracheal tubes.

One Possible Reason That There Are Not Any Really Large