Exchange and Transport Systems Flashcards
To understand how different organisms exchange and transport substances, and how these systems function
How does body size affect heat exchange?
The rate of heat loss from an organism depends on its surface area
If an organism has a large volume, its surface area is relatively small. This makes it harder for it to lose heat from its body
If an organism is small, its relative surface area is large so heat is lost more easily.
This means smaller organisms need a relatively high metabolic rate in order to generate enough heat to stay warm.
How does shape affect heat exchange?
Animals with a compact shape have a small surface area relative to their volume, minimising heat loss from their surface.
Animals with a less compact shape have a larger surface area relative to their volume, this increases the heat loss from their surface.
Why do single celled organisms not need a specialised exchange system?
Single celled organisms and some small muticellular organisms have large enough surface area to volume ratios to meet their gas exchange needs by diffusion across their surface.
Why do large multicellular organisms need a specialised exchange system?
Larger organisms (humans, other mammals, insects and fish) have relatively small surface area to volume ratios. They can not rely on diffusion across their surface alone to supply sufficient amounts of oxygen and glucose to all of their cells or remove waste products such as carbon dioxide.
In addition they are metabolically more active so, more oxygen is needed for respiration
Many cells are too far from the surface so diffusion is too slow/too inefficient to meet the needs of multicellular organisms
So larger organisms have developed specialised gas exchange systems which have adaptations to ensure the rapid diffussion of gases.
What features do insects have to limit water loss?
Waterproof covering over their body surfaces. This is usually a rigid outer skeleton (exoskeleton) covered with a waterproof cuticle.
Small surface area to volume ratio to minimise the area over which water is lost.
How does oxygen move throughout the insect?
Oxygen enters the insect through spiracles and into the tracheae. The trachae are supported by rings of chitin to prevent collapse. Spiracle valve open and closes to prevent water loss by evaporation.
Oxygen diffuses through the tracheae into the dividing tracheoles which extent through all body tissues
Oxygen is delivered directly to the respiring tissues.
How does oxygen diffuse in and out of the tracheal system?
Tissues respire using oxygen, which reduces the concentration of oxygen at the tissue.
Oxygen moves from an area of high concentration to low so moves from the tracheae to the tissue.
This lowers the oxygen concentration in the tracheae so oxygen moves into the tracheae from outside the insect via the spiracles.
How does CO2 move in and out of the tracheal system?
Respiration produces CO2, increasing the concentration at the tissue
CO2 moves from an area of high concentration at the tissue to the low concentration in the tracheae.
CO2 then moves from high concentration in tracheae to low concentration outside the insect via the spiracles.
What are spiracles and how do they benefit an insect?
Spiracles are pores that air enters through to be exchanged through the trachea
The spiracles open and close by a valve causing water vapour to evapourate from the insect and so for long periods of time the spiracles are closed to prevent water loss.
How does an insect get additional oxygen during flight?
When an insect is at rest, water can build up in the tracheoles.
During flight, the insect may partly respire anaerobically and produce some lactic acid.
This lowers the water potential of the muscle cells.
As the lactate builds up, water passes via osmosis from the tracheoles into the muscle cells.
This adaptation draws air into the tracheoles closer to the muscle cells and therefore reduces the diffusion distance for oxygen when its most needed.
What organ is responsible for gas exchange in fish and what adaptions does it have to make it more efficient at gaseous exchange?
The gills are the organ by which gases are exchanged between the fish and the water.
Gills enable fish to absorb oxygen and expel carbon dioxide.
Like the lungs, the gills have a large surface area for gas exchange.
How is water/oxygen transported through the fish?
Water carrying oxygen enters through the fish’s mouth, passes between the lamellae on the gill filaments where most of the oxygen is removed.
Finally water containing little oxygen and waste carbon dioxide leaves through gill opening
How are lamellae adapted for efficient gas exchange?
Many gill filaments, Each gill filament has MANY gill lamellae so a large surface area. Lamellae are at right angles to the filaments
Thin epithelium for short distance between water and blood
How does a counter current system benefit a fish?
Massively increase the fish’s ability to absorb oxygen from the water as a diffusion gradient is always maintained across the whole length of the gill lamellae
How does a counter current system work?
Water flows in the opposite direction to blood flow in the capillaries of the lamellae.
A concentration gradient is maintained all the way across the lamellae and almost all of the oxygen in the water diffuses into the blood.
Why is the volume of oxygen that has to be absorbed and carbon dioxide removed large in mammals?
They are relatively large organisms therefore have a large volume of living cells
They maintain a high body temperature and have a high metabolic and respiratory rate
Any respiratory surface should have the following properties
1) Large surface area
2) Permeable
3) Thin
4) Moist - gases diffuse more readily in solution
5) Efficient transport system….maintains a concentration gradient.
Why are lungs internal structures?
Air is not as dense as water and cannot support the delicate structure
A great deal of water would be lost from the body
In order to be an efficient gas exchange surface the lungs have a very small diffusion distance and large surface area and as a result are delicate. Therefore the lungs would be easily damaged if not an internal organ protected by the rib cage
