The Insect Gas Exchange System
Structure
Insects have an external gas exchange system - diffusion occurs outside of the body. Air travels through the spiracles which are valved openings positioned along both sides of the insect body.The spiracles lead into tracheal tubes which lead into tracheoles, that branch into nearly every single cell in the insect organism. The tracheoles are minute tubes which end within cells. Gas exchange only occurs at the end of each tracheole which is composed of a thin membrane that is pervious to oxygen and water.
What are the Advantages of an Insect's Environment?
Insects can almost live in any habitat. But for the insects which live and thrive on land, the amount of oxygen concentration in the air is very high. Terrestrial insects can easily ventilate oxygen in their gas exchange systems.
What are the Limitations of an Insect's Environment?
When the air is dry, it can cause the gas exchange surface (tracheoles) to become susceptible to dessication. Air is also dirty, so the dirt particles that might travel down the spiracles along with the oxygen could damage the delicate gas exchange surface. The temperature can fluctuate, resulting in surprising, unexpected climate changes that might affect the diffusion rate of oxygen.
What are the Advantages of an Insect's Gas Exchange System & How have they adapted to their Environment? (Compared to Fish)
1. An insect's gas exchange system is situated in the inside of the body to prevent dessication. Air is dry and the insect can risk dessication if the system was on the outside. Fish have their gas exchange system near the surface of their skin because they live in an environment where dessication is not an issue. Fish are typically always emerged in water and therefore are constantly moist.
2. Insects have hairs in the tracheal tubes to filter out unwanted particles that might accidentally travel in with the air through the trachea. Insects ventilate air whist fish ventilate water. Therefore fish have gill rakers which prevent food particles from sticking to the fine lamellae and the gill filaments, instead.
2. Insects have hairs in the tracheal tubes to filter out unwanted particles that might accidentally travel in with the air through the trachea. Insects ventilate air whist fish ventilate water. Therefore fish have gill rakers which prevent food particles from sticking to the fine lamellae and the gill filaments, instead.
3. The spiracles on the outside of the body can open and close to regulate the rate of which water is lost depending on the insect's surrounding environment. This is particularly important, as insects can prevent dessication in this dry, airy environment.
4. Insects also have air-sacs that are inside their bodies. They store air for extra supply when needed (particularly in flying insects). When the air-sacs are compressed by the insect, they expel air out or in from the trachae, and sometimes even providing insulation for the insect as extra warmth.
5. To properly support the gas exchange system, insects have hard rings of chitin which support the tracheal tubes that allow the air to travel down to the tracheoles. This is because of the gravity that acts upon the insect when they are in an air-supplied environment. Fish have adapted to rely on the buoyancy of the water to keep their gill filaments apart and separate instead.
4. Insects also have air-sacs that are inside their bodies. They store air for extra supply when needed (particularly in flying insects). When the air-sacs are compressed by the insect, they expel air out or in from the trachae, and sometimes even providing insulation for the insect as extra warmth.
5. To properly support the gas exchange system, insects have hard rings of chitin which support the tracheal tubes that allow the air to travel down to the tracheoles. This is because of the gravity that acts upon the insect when they are in an air-supplied environment. Fish have adapted to rely on the buoyancy of the water to keep their gill filaments apart and separate instead.
What are the Limitations of an Insect's Gas Exchange System?
Insects obtain oxygen through their external gas exchange system and rely heavily on diffusion itself. This is because insects do not have a circulatory system that enables them to pump oxygenated blood around the body, unlike fish and mammals. Many insects which are not adapted to dry environments may be susceptible to dessication and ultimately death because of their inability to control their rate of diffusion.
Insects have an extensive network of tracheoles to penetrate nearly every cell in their body. This is due to the fact that they do not have an transport system where the oxygen is transported throughout the body in blood. This is the reason why most terrestrial insects do not have red blood, unlike fish or mammals. Insects solely rely on diffusion. Therefore this gas exchange system that purely relies on simple diffusion alone is only suitable for small sized organisms.
Insects have an extensive network of tracheoles to penetrate nearly every cell in their body. This is due to the fact that they do not have an transport system where the oxygen is transported throughout the body in blood. This is the reason why most terrestrial insects do not have red blood, unlike fish or mammals. Insects solely rely on diffusion. Therefore this gas exchange system that purely relies on simple diffusion alone is only suitable for small sized organisms.
The chitin that is both the exoskeleton of the insect and also the substance which supports the tracheal tubes open is very heavy. This also limits how big a insect can grow, as once an insect passes a certain size, the ratio of how heavy the chitin is in relation to the rest of the insect's body will completely crush the insect's organs. This would result in the organs crushing down on the tracheal system and leading it to collapse as well.