Exam questions

• When first hatched, the young of some fish are less than 2mm long. Explain how they get enough oxygen without having gills?

  large SA : volume ratio, short diffusion distance across the whole body
• Mackerel have a lamellae thickness of 5 and have 32 lamellae per mm of gill length. They swim faster than toadfish which have thickness of 35 and 8 lamellae per mm. Explain how they swim faster.

  more lamellae= larger SA, more diffusion

  thinner lamellae = shorter diffusion distance and more diffusion as there is a higher oxygen uptake
• trachurus trachurus are a very active fish species. They weigh roughly 250g and their gill SA is 252,500 per mm. Explain how their features help them to be so active.

  the gills cover a large SA which suggests they need more oxygen from diffusion in order to make more ATP from respiration to be able to be active
• Describe and explain how the counter current system leads to efficient gas exchange across the gills

  water and blood move in opposite directions

  counter current maintains a concentration gradient across the whole length of gill between the blood and water
• describe the features of gills that give them a large SA

  lots of lamellae across the whole gill = more oxygen and more respiration
• explain two features of gills which allow efficient gas exchange

  lots of lamellae increase SA, countercurrent maintains gradient