It is restricted in its pressure due to the fact that the fragile gill gas exchange surface would rupture if the pressure is too high. It doesn’t seem that people posting their essays have been taught this structure and I’m starting to wonder if it is necessary although I do trust my teacher is right. These materials diffuse in and out of the cells. Fish, insects and mammals can assist the concentration gradient by ventilating the gas exchange membrane allowing them to control the rate of gas exchange, thus they are capable of a high metabolic rate so they can have an active lifestyle to meet the demands of the various environments they inhabit. This is to keep it moist. This maintains the concentration gradient allowing an efficient rate of diffusion.

Or would the below para be better? For the discussion part of the animal essay, do you only have to compare two animals? Gas exchange in insects involves air entering the tracheae through the spiracles openings , passing through the smaller tracheoles, and terminating in the tissues. I think I have read this somewhere before … is this copied from a text or from another student? These materials diffuse in and out of the cells. Insects 1 – air drawn in through spiracles small holes in side of thorax and abdomen and into hollow tubes called trachea held open by rings of chitin. This facilitates the constant diffusion of oxygen into the blood stream as a concentration gradient is maintained; low levels of oxygen in the blood are coming into contact with high levels of oxygen in water flowing in the opposite direction.

Compared to double circulation systems.

Fish are faster-moving and so need a higher surface area for gas exchange. Mammals are even more active exchangd so they need even more surface area for gas exchange. Instead humans use the tidal flow method of extraction which is not as efficient but helps to reduce water loss by holding some still air in the alveoli so is more suited to the terrestrial environment.

Gas Exchange – WGHS BAP Year 12

So is the humans discussion alright then? The membrane is semi-permeable allowing the gases tho diffuse through into the bloodstream and out to be exhaled.


These materials diffuse in and out of the cells. Thus, the variation in the circulatory systems exists due to the structure, size and requirement variation in different group of animals. Mammals also have surfactant to reduce surface tension, stop alveoli surfaces from sticking together and collapsing. External gills usually have a higher surface area but they are less protected.

We have taken many students through the steps of comparing the three groups for plants and animals – happy reading Once you’ve put esssy together we are more than happy to go from there Cheers ST Earthworms are limited to the soil because they must be kept moist, whereas humans and insects can occupy a wide range of habitats because their gas exchange systems are not dependant on their bodies staying moist.

External links

Insects 1 – air drawn in through spiracles small holes in side of thorax and abdomen and into hollow tubes called trachea held open by rings of chitin. As the diaphragm relaxes and the ribs swing back, CO2 which has diffused back into the alveoli as the pressure in the thoracic cavity increases forcing the lungs to deflate and exhale gases the alveoli are internal and so remain moist.

ncea gas exchange essay

Find what you need to know Choose a subject Choose a subject Choose a subject – Choose an achievement standard. In the earthworm soil which is acidc must be neutralised so that enzymes produced by oesophogeal glands can efficiently digest food into absorpable nutrients.

They have thin membranes so they have a high surface area to volume ratio. Also include any other relevant info like arrows to show the direction of blood flow, features eg “septum divides heart into two pumps “keeping oxygenated and deoxygenated blood separate.

ncea gas exchange essay

Unlike humans and insects, they move slowly and therefore do not require a large amount of oxygen. This gas exchange system enables mammals to grow large, as the SA of the alveoli is very large, moist and has a this semi-permeable membrane through which O2 can dissolve into our bloodstream and CO2 out to be carried by haemoglobin through our bloodstream to cells.


St 5 passes on to emz that hydra is fine as one of their animals but they must make sure that they can get enough material with the level of detail needed for yr Could you have a look and see what you think?

Also can i compare different animals for similarity and differences? Gas exchange surfaces have to be large a large surface area enables rapid gas exchange gqs, thin thin surfaces enable rapid diffusion of gasesand moist on which gases may dissolve and diffuse into and out of cells.

Carbon dioxide exits the blood by the same process, and is exhaled. The sizes of the gas exchange systems of these three animals differs according to their body size and metabolic rate. It is kept moist by mucus secreting cells, which is important because oxygen dissolves in the fluid.


Gas exchange in the fish and the human mammal involve the use of the circulatory system, whereas gas exchange in the insect does not. However, this system is very suitable gad animals like insects invertebrates with very small size and little metabolic activity. Thanks for your reply. Air travels down through hollow tubes called trachea which are supported by rings of chitin to keep them open.

ncea gas exchange essay

bas One circuit circulatory is system has blood flowing though heart just once, to be pumped to the gills in case of fish. Like most of the yr 12 bio students, I’m wondering just how to answer all four papers in 3 hours The division of heart also separates oxygenated and deoxygenated blood, making it more efficient because only oxygenated blood is transported to the tissues.

I am not quite sure about it.