Question

Air-breathing insects and vertebrates rely on aerobic metabolism for sustained production of ATP, but they effect oxygen supply by completely different means. Using two species of your choice (one for each taxon), compare and contrast the way these two groups deliver O2 from the environment to their tissues. Consider the scaling laws for the gas transport cascade and explain why there are no insects larger than 100g, but there are plenty vertebrates larger than that.

Answer 1

Comparing repiration in insects and vertebrates.

Insects like grasshoppers breathe through trachea and not lungs. Trachea are a set of tubes with holes along the abdomen. Air enters through trachea and diffuses into spiracles or blind ended trachea. Higher concentration of oxygen means more amount of oxygen can reach deeper ends of trachea in the insect.

Rabbit is a vertebrate and has highly developed respiratory system . Lungs are mainly responsible for the exchange of gases. Oxygen taken up by blood is distributed to the organs while carbon dioxide from the organs are pushed out through the nose. They do not contain trachea or spiracles.

Insects do not grow larger than a particular size. They breathe through trachea which are present throughout the body. Air just passes and diffuses through its body. If the percent of oxygen is less they do not get sufficient oxygen and finds it difficult to breathe. If this is the case when the insects are very small, then when they grow big in size they will hardly be able to survive. The tracheas will not function properly and gas exchange will not take place, eventually killing the insects. If the respiratory system in insects were replaced with lungs or gills then there are chances that they will grow big and survive well.