TOPIC 3 revision Flashcards
Insects require a specialised breathing system because:
Any two of the following:
Insects possess an exoskeleton; [1 mark]
(Which) prevents / reduces the diffusion of gases; [1 mark]
Many insects are highly active and so have a high metabolic rate / demand for oxygen; [1 mark]
Oxygen reaches the muscle cells as follows:
Air/oxygen diffuses along the trachea / tracheoles; [1 mark]
Oxygen dissolves in the fluid/water (at the end of the tracheoles); [1 mark]
Oyxgen diffuses from the fluid into the muscle cells; [1 mark]
The supply of oxygen to the flying muscles is affected as follows…
Any four of the following:
Lactate (produced by anaerobic respiration) builds up/accumulates in the cells; [1 mark]
(Lactate) lowers their water potential; [1 mark]
The water/fluid moves from the tracheoles into the cells by osmosis; [1 mark]
Oxygen diffuses directly into the cells; [1 mark]
The diffusion pathway/distance has been reduced; [1 mark]
Xerophyte plant adaptations
Feature 1: Rolled/curled up leaves
Explanation 1: (The shape of the leaves helps to) reduce the water potential gradient between inside the leaf and the air OR reduces the air movement across the stomata OR traps moist air inside OR reduces surface area for evaporation; [1 mark]
OR
Feature 2: Sunken stomata
Explanation 2: Reduces the air movement across the stomata OR traps moist air inside stomata OR reduces water potential gradient between leaf and air; [1 mark]
OR
Feature 3: Thick cuticle
Explanation 3: Reduces transpiration/evaporation via the leaf surface OR increases the diffusion distance; [1 mark]
OR
Feature 4: Hairs
Explanation 4: Trap air which becomes damp/moist/humid; [1 mark]
It is not beneficial for stomata to be on the top surface because:
Stomata could become blocked by drops of rain/water which would reduce gas exchange / uptake of carbon dioxide; [1 mark]
The stomata will be in direct sunlight which will increase water loss/evaporation /transpiration; [1 mark]
