AQA Bio A Level Unit 3 Flashcards
Describe the relationship between size of organisms and volume and surface area (2)
- As organisms get bigger/their size increases;
- Their surface area to volume ratio decreases; (and vice versa)
Why don’t small organisms such as flatworms have gills or circulatory systems? (2)
- They are small enough;
- Their surface area to volume ratio is big enough that they can rely on diffusion through their body surface;
The bear species found towards the poles are the largest whereas the bear species found in the tropics are much smaller. Why? (3)
- Larger bears have a smaller surface area to volume ratio, and lose much less heat (per kg of bear).
- They are adapted to cold climates.
- Smaller bears lose too much heat could not survive in the extreme cold
Which cells make up the exchange surface in the lung? (2)
1.Alveolar epithelial cell;
2. Capillary endothelial cell;
Outline the route taken by air from the atmosphere to alveolus. (5)
- Mouth/nose
- Trachea
- Bronchi
- Bronchioles
- Alveolus
Outline the processes required for inspiration (breathing in)
- Contraction of external intercostals moves ribcage upwards and outwards;
- Diaphragm contracts and moves downwards from domed to flattened shape;
- Volume of thorax increases;
- Pressure decreases below atmospheric;
Breathing out can be passive (no muscle contraction required). Which feature of lung tissue allows this?
- Its elasticity/elastic recoil
What is pulmonary ventilation a measure of?
The volume of air breathed in one minute.
How do you calculate pulmonary ventilation?
Multiply tidal volume by breathing rate.
What is tidal volume?
The volume of air breathed in one breath.
Explain three ways in which fish gills are adapted to give efficient gas exchange. (3)
- Large number of lamellae and gill filaments give large surface area; 2. The exchange surface is just 2 flattened cells, reducing diffusion distance;
- Counter-current (of water and blood) maintains diffusion gradient.
Which cells make up the exchange surface in the fish gill? (2)
- Lamella epithelial cell;
- Capillary endothelial cell;
Outline the route taken by air from the atmosphere to insect cells? (3)
- Spiracles;
- Trachea;
- Tracheoles;
Describe and explain the advantage of the counter-current principle in gas exchange across a fish gill. (4)
- Water and blood flow in opposite directions;
- Maintains concentration gradient;
- Equilibrium not reached;
- Diffusion along length of lamellae;
Why might insects close their spiracles? (1)
To reduce water loss.