Exchange in Transport Flashcards
In terms of surface area to volume ratio when is exchange the most effective?
Surface area must be large compared to the volume
What are the features of specialised exchange surfaces?
1) Large surface area to volume ratio
2) A thin diffusion pathway
3) A partially permeable exchange surface
4) Movement of the internal/external environment
How do insects reduce water loss?
Waterproof coverings, small surface area to volume ratio prevents losing water
How are insects developed to respire?
They have tracheoles and spiracles which act as valves allowing gas flow.
How are respiratory gases moved in and out of an insects tracheole system?
1) Diffusion- created by respiration i.e. oxygen is being used at the end of the tracheole creating a gradient
2) Ventilation
Why do fish need a specialised gas exchange mechanism?
Waterproof coverings, small surface area to volume ratio prevents losing water
What are the components of fish gills?
Gill filaments- stacked in a pile
Gill lamellae- at right angles to the filaments
What mechanism do fish utilise to oxygenate themselves?
The counter current flow
What are the adaptations of gill lamellae?
1) Large and flat
2) Large surface area
3) Rich blood supply
What are the adaptations of the gill filaments?
Kept apart by water which exposes a large surface area
What is the counter current principle?
1) Water passes over the gills in the opposite direction to blood
2) The water has a higher concentration of oxygen than the blood
3) Diffusion gradient is created and oxygen passes from the water to the blood
What makes plant leaves good at gas exchange?
1) Short diffusion pathway
2) Large surface area to volume ratio
3) Thin and flat- larger surface area
4) Many stomata on the surface of a leaf
What are the adaptations of roots for water transport?
1) Each root has many root hair cells- large SA
2) Short diffusion pathway
What is the apoplastic pathway?
1) Water is drawn into root hair cells
2) Cohesive properties pulls more along
3) Cohesive tension is created which draws the water along cell walls
What are the steps in the passage of water to the xylem?
1) Water from the root hair cells reaches the endodermis
2) The casperian strip prevents water passing further
3) Water is forced into the protoplast
4) Water moves into the xylem by osmosis
What is transpiration?
The process which pulls water up the xylem
What are the steps of transpiration?
1) Movement of water out through stomata
2) Water is replaced by water from the cell walls of mesophyll cells
3) Water from the xylem enters the mesophyll cells
4) Water enters the xylem from the roots
What are the factors that affect the rate of transpiration?
1) Humidity- affects the water potential gradient between the leaf and the atmosphere
2) Wind- affects the water potential gradient between the leaf and the atmosphere
3) Temperature- (see above) also it alters kinetic energy
4) Light- stomata are closed at night
What are the 2 factors responsible for water movement up the xylem?
1) Cohesion-tension
2) Root pressure
What is the cohesion tension theory?
1) Water is lost by transpiration
2) Hydrogen bonds formed allows for cohesion
3) Water forms a continuous pathway from mesophyll cells through the xylem
4) As water is lost at the leaf more molecules are drawn up
5) Transpirational pull put xylem under pressure
How do plants limit water loss?
1) Sunken stomata
2) Rolling of leaves
3) Thick cuticle
4) Hairy leave
