Give some examples of things that need to be exchanged between an organism and its environment.

What are the two ways this exchange can take place?

Give an example of each type of exchange

In terms of a surface area to volume ratio, what must it be for exchange to be effective and efficient?

Some organisms have a sa:vol ratio that is too large to ensure an efficient gas exchange rate (some cells too far away). What are the two features organisms may have evolved to overcome this problem?

What are some of the features of a specialised exchange surface?

How can the relationship between these factors be expressed? (equation)

Why are gas exchange surfaces often located inside an organism?

What does this mean to organism needs?

What is the problem with all terrestrial organisms (live on land)?

What does this mean they need to do?

However what features of an efficient gas exchange surface contradict with this?

What two features do terrestrial organisms exhibit to reduce water loss?

This means that insects cannot use their body surface to diffuse gases in the same way as ______ ______ _________

Instead they have developed an internal network of tubes called _______

Why are the tracheae supported by strengthened rings?

What do the tracheae divide into?

In which ways to respiratory gases move in and out of the tracheal system?

Explain how gases move through the tracheal system along a diffusion gradient

Diffusion in air is much quicker than in water. What does this mean?

How does ventilation further speed up the exchange of respiratory gases?

Through which structures do gases enter and leave the tracheae?

The spiracles are open and closed by valves. What is allowed to happen when the spiracles are open?

So why do insects keep their spiracles closed most of the time?

What is a limitation of the tracheal gas exchange system?

Fish have a ____________ and ___ _____ outer covering

Being relatively large they have a _____ sa:vol ratio

This means their body surface is not adequate to supply & remove their respiratory gases. What is the name of the specialised internal gas exchange surface inside fish?

What are gills made up of?

The gill filaments are stacked up in a pile. What structures are at right angles to the gill filaments?

What do gill lamellae increase?

The position and arrangement of the gill filaments & lamellae mean that water flow over them and blood flow within them are in opposite directions. What name is given to this principle?

What does the countercurrent exchange principle allow for?

Why is there a fairly constant rate of diffusion across the entire length of the gill lamellae?

In plants, why is there a reduced need for gas exchange with the external air?

In which 2 ways is gas exchange in plants similar to gas exchange in insects?

In addition, plants have a very _____ surface area compared to the volume of living tissue

This means no specialised gas exchange system is needed. Where does most of the gas exchange in the plant happen?

What are the three adaptations of the leaf that make it suitable for rapid diffusion?

Each stomata is surrounded by a pair of what?

What can these cells do?

Why is this important?

How do they use the stomata to do this?

________ is adequate for transport over short distances

Mammals however have a very small s.a:vol ratio and therefore require a mass __________ _______

Whether or not there is a specialised transport medium and/or a pump depends on what two factors?

How many features of a mass transport system are there?

One feature is that there needs to be a suitable medium in which to carry materials. What is this medium in mammals?

Why is this medium usually a liquid based on water?

Another feature is that there is a closed system of what that contain the transport medium?

Why do the vessels form a branching network?

Moving the transport within vessels requires a _______ difference between one part of the system and another

In which two main ways is this achieved?

Give an example of another feature of transport systems that maintains mass flow movement in one direction?

What is the final feature?

Mammals have a _______ circulatory system

What does this refer to?

Why is this necessary? (in terms of pressure)

For what two reasons is it necessary that substances are delivered to the rest of the body quickly?

What are the three types of vessels that make up the circulatory system of a mammal?

The transport system is used to move substances longer distances. What process is the final part of the journey into the cells?

Why is the final exchange from capillaries into cells rapid?

Arteries, arterioles (smaller arteries) and veins all have the same basic layered structure. What is this structure?

What is the function of the tough outer layer?

What is the function of the muscle layer?

What is the function of the elastic layer?

Why is the thin inner lining (endothelium) smooth?

What is the lumen?

Out of arteries, arterioles, capillaries and veins, which has the thickest muscle layer?

Why is this necessary?

However arterioles have a thinner elastic layer than arteries. Why is this?

In which vessels are valves present throughout?

Explain why there are valves in veins but no valves in arteries (except leaving the heart)

Why is the muscle, elastic and overall thickness of the walls in veins relatively thin?

Give some features of capillary structure that make it suited to its function of exchanging metabolic materials between the blood and the tissues

Why are the spaces between the endothelium lining cells useful?

What name is given to the liquid which bathes the tissues?

Tissue fluid is formed of blood plasma. Why is blood plasma forced out the capillary wall at the arteriole end of capillaries?

Tissue fluid is formed by ultrafiltration rather than diffusion. Explain why

Give some examples of ways by which materials are now exchanged between the tissue fluid and the tissues

Why does tissue fluid return by diffusion at the venous end of the capillary bed?

Solutes (salts, carbon dioxide etc) enter the blood by diffusion ____ their concentration gradient

Why has a water potential gradient been set up between the tissue fluid and the blood?

Not all the fluid that left returns. Where does this excess tissue fluid drain to?

Lymph vessels have ____ walls

So tissue fluid can easily _______ inside, forming lymph