practice paper questions Flashcards
Describe and explain one feature of the alveolar epithelium that makes the epithelium well adapted as a surface for gas exchange. Do not refer to surface area or moisture in your answer. [2 marks]
- single layer of cells reduces diffusion pathway
OR - permeable so allows diffusion of O2/CO2
explain how the counter current principle allows efficient oxygen uptake in the fish gas exchange system [2 marks]
- blood and H2O flow in opposite directions
- concentration gradient maintained along the length of the gill
describe and explain the mechanism that causes the lungs to fill with air [3 marks]
- diaphragm contracts AND external muscles contract
- causes volume inside thorax to increase, reducing the pressure inside the thorax
- air moves down pressure gradient
Two solutions often used stain tissues are haematoxylin solution and iodine solution
- haematoxylin stains DNA a blue colour
- iodine solution stains starch a blue-black colour
The scientist used haematoxylin solution and not iodine solution to stain lung tissue. Suggest why. [2 marks]
- lungs don’t contain starch
- haematoxylin makes the nucleus visible as the nucleus contains DNA
Particulate matter is solid particles and liquid particles suspended in air. Polluted air contains more particulate matter than clean air.
A high concentration of particulate matter results in the death of some alveolar epithelium cells. If alveolar epithelium cells die inside the human body, they are replaced with non-specialised, thickened tissue.
Explain why the death of alveolar epithelium cells reduces gas exchange in human lungs. [3 marks]
- lower SA
- larger distance for diffusion
- smaller rate of gas exhange
Describe and explain the advantage of the counter-current principle in gas exchange across a fish gill [3 marks]
- H2O and blood flow opp. to each other
- maintains conc. gradient across whole gill
- meaning, diffusion can occur across the whole length of the lamallae
Sunflowers are not xerophytic plants. The scientists repeated the experiment in xerophytic plants.
Suggest and explain one way the leaf of xerophytic plants would be diff. from the leaf growth of sunflowers [2 marks]
- leaf growth is slow
- smaller number of stomata for gas exchange
Use your knowledge of gas exchange in leaves to explain why plants grown in soil with very little water only grow slowly [2 marks]
- stomata close
- meaning, less CO2 uptake for less photosynthesis/glucose production
Describe the pathway taken by an oxygen molecule from an alveolus to the blood [2 marks]
- across alveolar epithelium
- into epithelium of capillary
explain 3 ways in which an inseacts trachael system is adapted for efficient gas exchange [3 marks]
- large number of branches of tracheoles increases SA
- thin walls allows oxygen to be transferred directly to the cell requiring it
- trachae provide tubes full of air, meaning fast diffusion into insect tissues
The damselfly larva is a carnivore that actively hunts prey. It has gills to obtain O2 from water.
Some other species of insect have larvae that are a similar size and shape to damselfly larvae and also live in water. These larvae do not actively hunt prey and do not have gills.
Explain how the prescence of gills adapts the damselfly to its way of life. [2 marks]
- high metabolic rate
- therefore, uses O2
explain 2 ways in which the structure of fi9sh gills is adapted for efficient gas exchange [2 marks]
- gill filaments increase SA, meaning more gases are able to diffuse
- thin surface, therefore, short diffusion pathway
explain how the counter-current mechanism in fish gills ensures the maximum amount of the oxygen passes into the blood flowing through the gills
- water flows in opp. directions
- water has higher oxygen concentration than blood
- diffusion occurs throughout length of gill
