module 3: fish and insects

Question 1

what system do fish use for gas exchange

Answer 1

counter-current- water and blood flow in opposite directions to maintain conc gradient

Question 2

how counter-current system works

Answer 2

1- water enters through fish mouth and passes through gills
2-each gill has gill filaments with lots of lamellae for a large surface area, each gill supported by gill arch
3- gill plates have blood capillaries and thin surface layer of cells for fast diffusion
4- blood flows over gills counter currently so conc of o2 in water is always higher than in blood

Question 3

how are gills ventilated

Answer 3

1- fish opens its mouth and buccal cavity floor lowers
2- volume of buccal cavity increases so pressure decreases and water is sucked in
3- when fish closes mouth floor of buccal moves up
4- volume in buccal decreases and pressure increases so water forced out across gill filaments
5- protective flap- operculum- forced open allowing water to leave gills

Question 4

how are insects ventilated

Answer 4

1- air diffuses through spiracles on surface of body to the trachea
2- o2 travels down conc gradient towards body cells
3- trachea branch into tracheoles with thin permeable walls
4- 02 dissolves into fluid and diffuses into cells

Question 5

what circulatory system do fish have

Answer 5

single closed

Question 6

what circulatory system do insects have

Answer 6

open