ventilation in fish and insects-exchange surfaces and breathing

Question 1

adaptation of gills

Answer 1

• each gill made of lots of thin branches called gill filaments/primary lamellae=increase SA
• gill filaments covered in tiny structures called gill plates/secondary lamellae
• gill plates have lots of blood capilleries and thin=speed up diffusion

Question 2

counter current system in fish

Answer 2

blood flows through gill plates in one direction and water flows over in opposite direction
-helps maintain a large concentration gradient

Question 3

how are fish gills ventilated

Answer 3

• fish opens mouth, lowers floor of buccal cavity (space inside mouth)
• vol of buccal cavity increases, decreasing pressure inside= water is sucked in
• fish close mouth, buccal cavity floor raised, vol decreases, pressure increases= water is forced out the cavity across the gill filaments
• increase in pressure forces the operculum on each side of head to open, allowing water to leave the gills

Question 4

ventilation in insects

Answer 4

• air moves into the tracheae through the spiracles on the insects surface.
• O2 travels down the concentration gradient towards the cells
• CO2 from the cells moves down its own concentration gradient towards the spiracles to be released into atmosphere
• trachea branch off into smaller tracheoles which have thin permeable walls and go to individual cells. O2 dissolves into the fluid in the tracheoles and diffuses from the fluid into body cells
• CO2 diffuses in opposite direction
• insects use rhythmic abdominal movements to change the volume of their bodies which move air in and out of spiracles

Question 5

steps to dissecting insect

Answer 5

• cut and remove piece of exoskeleton from the abdomen
• use saline solution/water= will be able to see tracheae
• can examine trachea under light microscope using a wet mount slide

Question 6

how can insects reduce water loss

Answer 6

-spiracles on outer surface can be opened or closed by sphincters

Question 7

structure inside insects

Answer 7

• tracheae lead away from the spiracles (lined with spirals of chitin which keep them open)
• tracheae branch to form narrower tubes until they divide into the tracheoles (no chitin lined so permeable to gases), runs through most cells
• O2 dissolves in the moisture on the walls of the tracheoles and diffuses into surrounding cells

Question 8

adaptations in insects for when O2 demands are high

Answer 8

-lactic acid builds up in the tissues results in water moving out of the tracheoles by osmosis=exposes more SA for gas exchange

Question 9

extra adaptions of gills for effective gas exchange

Answer 9

• tips of adjacent gill filaments overlap= increases resistance to the flow of water over the gill surfaces and slows down movement of water=more time for gas exchange
• water and blood flow in opposite directions which ensures a steep conc gradient =more gas exchange