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src="/qa/attachment/10485948/" alt="Screenshot 2019-09-24 at 1.18.49 PM.png" />Heya am not sure on this question

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Q1. Some bony fish are known to control their buoyancy in water using swim bladders. These bladders are filled
with a gas to maintain neutral buoyancy at varying water depths.
If you own a goldfish, you may have seen it rise to the surface to take "gulps" of air; they actually expell/ingest
air through their gut, which is connected to their swim bladder. Fish whose swim bladders are connected to
their gut are called phytosomes.
Other fish, such as the pink snapper, are physoclisti. Their swim bladders are not connected to their gut.
Instead, they can alter the volume of their swim bladders. Through a complicated process, they can increase the
concentration of oxygen molecules in their blood. The blood then travels through a rete mirabile, a wonderful net
of arteries and veins where these molecules are transferred into the gas gland through countercurrent exchange.
The gas gland is directly connected to the swim bladder, and can secrete these molecules (which now act as a
gas) into the bladder when necessary. The swim bladder itself has flexible walls, and will change shape when
exposed to different pressures. A simplified diagram of this system is shown in Figure 1.
Swim bladder
Blood Flow
Molecule diffusion
Gas plant
Molecular concentration
Foota mirabile
9110 3 100
70 90
120 120
Figure 1: Diagram of the rete mirabile, gas gland and swim bladder system. The numbers here indicate concentrations.
Credit to Sholokhov, CC BY-SA 3.0, https://commons. wikimedia. org/w/index . php?curid=25711717
(a) Pink snappers can be found up to depths of 0.200 km. Calculate the pressure of the water at these depths.
Assume the density of salt water is pwater = 1030kg/m".
(b) Pink snappers can grow up to 130 cm long and weigh up to 20 kg. Let us focus on a modestly sized pink
snapper, whose mass is 15.0 kg and whose volume is 0.0100 m (when their swim bladder is empty)
i) What must the volume of the swim bladder be for the snapper to maintain neutral buoyancy? (Assume
that the mass of the gas inside the bladder is negligible. Treat the water as incompressible and hence
as having a constant density - this is a reasonably accurate simplification for the depths considered).
ii) Do you think the snapper needs to increase or decrease the amount of gas in its swim bladder to
maintain neutral buoyancy as it goes from just below the water's surface to a depth of 100 m? Explain
your answer.

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{c} The concentration of mygen mnlemlles inside the pink snapper’s rate mimbiie increases quite dralnaticall}r
as it approaches the gas gland. Small-diameter blood vessels then assist diffusion of mcygen into the gas
gland. Let us consider a cylindrical section of the rate mimbi-ie outside the gas gland with a length I, radius
m and pressure difference mrer this length of flPa. If inside the gas gland, a cylindrical section of the
same length-i has a pressure difference 25E times larger1 what must the radius ofthis cylindrical section be
compared to the original radius m to maintain the same blood flow rate in the rate numbilc?

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