Gaseous Exchange In Insects & Bony Fish (Adaptations)

Question 1

What do bony fish need a constant flow of, to allow gaseous exchange to take place?

Answer 1

Water

Question 2

Explain the stages of water flow over the gills (4):

Answer 2

Anatomical: Mouth opened, buccal cavity floor is lowered
Volume: This increases the vol in the buccal cavity
Pressure: As a result the pressure in cavity drops water moves in. At the same time opercular valve shuts and the operculum cavity expands. The floor of the buccal cavity begins to move up and so increases the pressure forcing the water to move from the buccal cavity over the gills.
Water Movement: Mouth closes, operculum opens and the sides of the operculum cavity moves inwards (all these actions increase pressure, in operculum cavity and force water over gills and out the operculum). The floor of the buccal cavity is steadily moved up, maintaining a flow of constant water over gills.

Question 3

Spiracles

Answer 3

Tiny pores on the side of the insect abdomen (and sometimes thorax) which open into breathing tubes called tracheae

Question 4

Tracheae

Answer 4

Plural of trachea.. insects have many tracheae which branch into smaller tracheoles

Question 5

Haemocoel

Answer 5

The internal cavity of the insect

Question 6

Chitinous tubes

Answer 6

Tubes reinforced with chitin

Question 7

What’s tracheal fluids and how is it withdrawn during periods of oxygen demand?

Answer 7

Towards the end of the tracheoles there is tracheal fluid which limits the penetration of air for diffusion. However when oxygen demands builds up, lactic acid builds up in the tissues, resulting in water moving out of the tracheoles by osmosis. This exposes more surface area for gas exchange.

Question 8

What system provides all the oxygen needed by the cells of an insect

Answer 8

The tracheal system

Question 9

How is the extent of gaseous exchange controlled in most insects?

Answer 9

Through the opening and closing of the spiracles

Question 10

Spiracles (structure and function):

Answer 10

• Tiny pores
• Lining along the thorax and abdomen
• Have the ability to open and close (sphincter muscles) which helps aid/ increase oxygen intake during high demands
• These sphincters are kept closed as much as possible to minimise water loss)

Question 11

Tracheae (structure and function):

Answer 11

• Leading away from the spiracles, they’re the largest tubes of the insects respiratory system (1mm).
• Carry air into the body and they run both into and along the body of the insect.
• Tubes lined with chitin (keeps the open if they’re bent or pressed, no collapsing or bursting).
• It’s relatively impermeable to gases (therefore little gaseous exchange takes place in the tracheae).

Question 12

Tracheoles (structure and function):

Answer 12

• A network of minute tubes (0.6-0.8 micrometers)
• Each tracheole is a single greatly elongated cell with no chitin lining (so they’re freely permeable to gases).
• Because of their very small size they spread through about the tissues of the insects running in between individual cells.
• Where most gaseous exchange takes place between the air and the respiratory cells.

Question 13

Explain the different types of system with water flow in bony fish and cartilaginous fish

Answer 13

Counter current system, removes 80 percent of oxygen from water

Parallel system, removes 50 percent of oxygen from water

Question 14

Name three main/basic adaptations fish have with their gaseous exchange system

Answer 14

• Gills have a large SA for diffusion
• Rich blood supply (maintain steep concentration gradient)
• Thin layers so diffusing substances have short distance to travel

Question 15

Counter current system?

Answer 15

Blood and water travel in opposite directions, therefore a oxygen concentration gradient is constantly maintained all along the gill. Oxygen continues to diffuse down the concentration gradient so a much higher level of oxygen saturation of the blood is achieved

Question 16

Parallel system

Answer 16

Blood in the gills and water flowing over the gills travel in the same direction, which gives an initial steep oxygen concentration gradient between blood and water. Diffusion takes place until the concentration of oxygen reached equilibrium in the water and gills, then no net movement of oxygen into the blood occurs.

Question 17

The tips of adjacent gill filaments

Answer 17

They overlap, increasing the resistance to the flow of water over the gill surfaces and slows down the movement of water. As a result provides more time for gaseous exchange to take place.