fish transport + ventilation + exchange surfaces

Question 1

what type of circulatory system do fish have

Answer 1

single closed circulatory systems

Question 2

single circulatory system definition

Answer 2

a circulatory system where blood flows through heart once during a complete circuit of the body

Question 3

what are disadvantages of a single circulatory system

Answer 3

• limits rate of O2 delivery to respiring tissues
• limits rate of waste removal
• blood pressure drops considerably so blood flow back to heart is very slow

overall less efficient

Question 4

what are 4 reasons fish able to cope with a single circulatory system despite being very active

Answer 4

• the countercurrent exchange mechanism means they can take up a lot of O2 from water
• body weight is supported by water
• they do not thermoregulate internally so lower metabolic demand
• they tend to be
  small organisms so lower metabolic demand (compared to most mammals)

Question 5

where does gas exchange occur in fish

Answer 5

gills

Question 6

adaptations + functions of gills that make it an efficient exchange surface

Answer 6

• constantly flowing blood supply to maintain conc gradient as substances are brought away once exchange has occurred
• extensive capillary network to maximise rate of gas exchange
• counter current flow of blood and water ensures conc gradient is maintained across whole capillary length, so water with highest [O2] is found next to most deoxygenated blood
• large SA with 4 gill arches on each side
• attached to gills arches are gill filaments which have many fine branches (lamellae) exposed to the water increasing SA:V so high rate of diffusion
• gill lamellae are very thin so short diffusion distance between blood flowing through and water

Question 7

what is the function of gill arches

Answer 7

support of the gills

Question 8

what are gill lamellae

Answer 8

fine branches on gill filaments

Question 9

is the [O2] higher in water or in air

Answer 9

[O2] is higher in air, as O2 dissolved less readily in water than in air

in air [O2] = 20% approx
in water [O2] = 1% approx

Question 10

outline the path O2 takes in fish

Answer 10

water - gills - gill filaments - gill lamellae - blood vessels where it travels around fish body

Question 11

what is a buccal cavity

Answer 11

a space for water to flow into fish mouth, depending on pressure differences

Question 12

how does water flow regarding pressure

Answer 12

from high to low pressure

Question 13

what occurs during inspiration in fish

Answer 13

• mouth open
• floor of buccal cavity is lowered increasing volume of buccal cavity + operculum is pulled shut
• this decreases pressure in buccal cavity
• pressure in mouth < pressure outside mouth
• this causes water to flow inside fish mouth

Question 14

what occurs during expiration in fish

Answer 14

• mouth closed
• floor of buccal cavity is raised decreasing volume of buccal cavity
• this increases pressure in buccal cavity
• pressure in buccal cavity > pressure in gill cavity
• water flows to gill cavity
• this increases pressure in gill cavity
• pressure in gill cavity > pressure outside fish
• this causes the operculum to be forced open
• water flows out of gills

Question 15

what is the operculum

Answer 15

a flap of tissue covering gills