Topic 3 Flashcards
A countercurrent system means that:
The water flowing over the gills flows in the opposite direction to the blood in the capillaries (inside the lamellae); [1 mark]
AND
This functions as an adaptation for gas exchange because:
This maintains the diffusion gradient along the whole length of the capillary/gill/lamella OR this ensures that the concentration of oxygen in the water is always higher than the concentration in the blood flowing alongside / next to it; [1 mark]
This means that diffusion of oxygen into the blood takes place along the whole length of the capillary/gill/lamellae / along the greatest possible surface area; [1 mark]
The student could use this agar to investigate the effect of surface area : volume ratio on the rate of diffusion using the following method:
Measure out five test tubes / beakers of (hydrochloric) acid AND ensure that all contain the same volume of acid /a stated volume of acid; [1 mark]
The volume of acid must be enough to ensure that all of the cube sizes are fully submerged when placed in the acid; [1 mark]
Place each cube into a separate container and start a stopwatch; [1 mark]
Leave the cubes in the acid for (a specified length of time) and then use a ruler to measure how much of the cube has changed colour / become colourless OR leave the cubes in the acid until they completely change colour / become colourless and then record how long it took; [1 mark]
Repeat experiment (at least) twice more for each cube size AND calculate a mean for each cube size; [1 mark]
Ensure that each beaker is left undisturbed during the experiment OR that the temperature of each beaker is kept the same; [1 mark]
Calculate the surface area:volume ratio AND the rate of diffusion for each cube; [1 mark]
most single-celled organisms are limited in size to around 100 μm because:
Larger cells will have a smaller surface area : volume ratio, SO diffusion of oxygen/glucose/ other named nutrient will be too slow to meet metabolic demands; [1 mark]
Xerophytic features include:
Description: Sunken stomata
Explanation: these trap water vapour, reducing the water potential gradient between the inside of the leaf and the outside; [1 mark]
OR
Description: Hairs surrounding stomata
Explanation: these trap water vapour, reducing the water potential gradient between the inside of the leaf and the outside; [1 mark]
OR
Description: Thick waxy cuticle / layer of epidermis cells
Explanation: this reduces evaporation; [1 mark]
OR
Description: Small surface area
Explanation: this reduces the number of stomata; [1 mark]
OR
Description: Densely packed cells within the leaf
Explanation: this reduces the evaporation of water from the surface of these cells; [1 mark]
Small physical exertion such as walking 100 yards becomes difficult with fibrosis because:
Less CO2 is removed and less O2 is inhaled/taken in/absorbed; [1 mark]
So there is less aerobic respiration; [1 mark]
So there is less ATP produced which is required for muscle contraction/muscle fatigue develops sooner; [1 mark]
Paralysis of the diaphragm can lead to reduced lung function because:
The diaphragm will not contract; [1 mark]
So there is no increase in volume/decrease in pressure in the chest/thoracic cavity; [1 mark]
This means that less air moves into the lungs because the pressure gradient is not as steep/not created; [1 mark]
Group B should have been treated:
By giving them a spray that did not contain albuterol; [1 mark]
But otherwise treated the same; [1 mark]
Asthma may lead to serious health conditions as:
There is reduced airflow into the lungs; [1 mark]
As a result, less oxygen is absorbed AND less carbon dioxide is removed; [1 mark]
This means there is a lack of oxygen available for aerobic respiration OR carbon dioxide can build up to toxic/dangerous levels; [1 mark]
