Exampro - ASG 2 Flashcards
The adult damselfly uses a tracheal system for gas exchange.
Explain three ways in which an insect’s tracheal system is adapted for efficient gas exchange. (3 marks)
- Thin walls = short diffusion distance to cells
- Highly branched = large surface area for gas exchange
- Trachea provide tubes full of air so fast diffusion into insect tissue
The damselfly larva is a carnivore that actively hunts prey. It has gills to obtain oxygen 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 presence of gills adapts the damselfly to its way of life. (2 marks)
- DL - higher metabolic/ respiratory rate
- Uses more oxygen
Suggest two ways the student could improve the quality of her scientific drawing of this gill. (2 marks)
- Don’t shade
- Single lines
- Don’t cross label lines
Give three environmental variables that should be controlled when growing the plants before treatment with the different sprays. (2 marks)
- Temperature
- Light intensity
- Soil pH
Suggest one reason why the scientists ensured the temperature remained constant and one reason why the leaf discs were shaken. (2 marks)
- Temp = No change in shape
- Shaking = so all surfaces of the leaf discs are exposed to water
Haemoglobin (1 mark)
- Quaternary
- Formed by condensation reaction
- Contains nitrogen
Cellulose (1 mark)
- Formed by condensation reactions
Starch (1 mark)
- Formed by condensation reactions
The oxygen dissociation curve of the fetus is to the left of that for its mother. Explain the advantage of this for the fetus. (2 marks)
- Higher affinity - Loads more o2
- Therefore oxygen moves from mother
After birth, fetal haemoglobin is replaced with adult haemoglobin. Use the graph to suggest the advantage of this to the baby. (2 marks)
- Low affinity
- Oxygen to respiring tissues
Hereditary persistence of fetal haemoglobin is a condition in which production of fetal haemoglobin continues into adulthood. Adult haemoglobin is also produced.
People with HPFH do not usually show symptoms. Suggest why. (1 mark)
- Enough adult Hb produced
Explain how the cuticle reduces water loss. (1 mark)
- Waxy - waterproof - water can’t pass through
Explain how one of the other labelled parts reduces water loss. (2 marks)
- Stoma can close
- Reduces area for evaporation or transpiration
