Exchange surfaces- Insect and Fish gas exchange

Question 1

Define the term exoskeleton

Answer 1

An external skeleton of some organisms- made of chitin and is waterproofed to reduce water loss.

Question 2

Define the term spiracle

Answer 2

Small openings along the thorax and abdomen of an insect that open and close to control the amount of air moving in and out of the gas exchange system.

Question 3

Define the term trachea

Answer 3

The main airway, supported by incomplete rings of cartilage, which carries warm moist air down form the nasal cavity into the chest.

Question 4

Define the term tracheoles

Answer 4

A small pipe that branches of a trachea in insects and is used for gas exchange.

Question 5

Define the term tracheal fluid

Answer 5

Fluid found at the ends of the tracheoles in insects that helps control the surface area available for gas exchange and water loss.

Question 6

Outline the structure of the insect gas exchange system and describe the way oxygen reaches the body cells.

Answer 6

1. Air moves into the tracheae through pores on the surface called spiracles.
2. O2 travels down the conc gradient towards the cells.
3. CO2 from the cells moves down its own conc gradient towards the spiracles to be released into atomsphere.
4. The tracheae branch off into smaller tracheoles which have thin permeable walls and go to individual cells.- they also contain fluid which oxygen dissolves in
5. The oxygen then diffuses from this fluid into body cells- CO2 diffuses in the opposite direction.

Question 7

Explain why insects will tend to keep spiracles closed when oxygen demands are very low.

Answer 7

Spiracles can be opened and closed by sphincters- the spiracle sphincters are kept close as much as possible to minimise water loss.

Question 8

Describe the adaptations of the insect gas exchange system that make it an efficient exchange surface.

Answer 8

1. The tracheoles provide a large SA for gas exchange

2. The tubes are thin- allows the tracheoles to go close to cells- minimise diffusion distance

Question 9

Describe how activity changes the volume of tracheal fluid in the tracheoles, and explain the value of this occurring.

Answer 9

1. When oxygen demands builds up- Lactic acid builds up in the tissues- results in water moving out of the tracheoles (tracheal fluid) by osmosis- exposes more SA for gaseous exchange.

Question 10

Describe two adaptations that insects with very high energy demands have to increase the efficiency of their gas exchange system.

Answer 10

1. Mechanical ventilation of the tracheal system- air is actively pumped into the system by muscular pumping movements of the thorax and/or abdomen. These movements change the volume of the body- changes the pressure in tracheae and tracheoles- air is drawn into or forced out of them as pressure changes.
2. Collabsible enlarged tracheae or air sacs which act as resevoirs- these are used to increase the amount of air moved through the gas exchange system- usually they are inflated or deflated by the ventilating movements of the thorax and abdomen.

Question 11

Describe the advantages of, and challenges faced by, gas exchange systems operating in water rather than air.

Answer 11

Advantages:
1. Water loss isn’t an issue
2. Water provides structural support which air doesn’t
Disadvantages:
1. Much lower oxygen concentration- lower conc. gradient- more difficult to obtain sufficient O2
2. Water is more viscous and dense than air.

Question 12

Define the term opperculum

Answer 12

The bony flap covering the gills of bony fish. Part of the mechanism that maintains a constant flow of water over the gas exchange surfaces.

Question 13

Define the term buccal cavity

Answer 13

The space behind the mouth in a fish.

Question 14

Define the term opercular valve

Answer 14

The flap that allows the oppeculum to be moves outwards whilst keeping it closed

Question 15

Define the term gill arch

Answer 15

The bony structure that supports the gill filaments,

Question 16

Define the term gill filament

Answer 16

A thin projection from the gill arch creating a large SA- need a flow of water to keep them apart to expose th large SA

Question 17

Define the term gill plates

Answer 17

Gill plates are large stacks of gill filaments

Question 18

Define the term gill lamellae or plates

Answer 18

Raised plates on the surface of gill filaments which in total create a large SA for gas exchange

Question 19

Label and annotate a diagram showing the features of the gas exchange system in bony fish.

Answer 19

Find an online labelling diagram

Question 20

Describe the mechanism of inspiration in bony fish.

Answer 20

1. Mouth opens and floor of buccal cavity is lowered
2. Expansion of buccal cavity increases the volume and reduces pressure causing water to enter via the mouth (buccal cavity pressure pump)
3. At the same time the opercular valve is shut and the opercular cavity containing the gill expands
4. This lowers the pressure in the opercular cavity containing the gills.
5. The floor of the buccal cavity starts to move up, increasing the pressure there so water moves from the buccal cavity over the gills to the opercular cavity

Question 21

Describe the mechanism of expiration in bony fish.

Answer 21

1. Mouth closes, the operculum opens and the side of the opercular cavity move inwards.
2. These actions increase the pressure in the opercular cavity and force water over the gills and out of the operculum.
3. The floor of the buccal cavity is steadily moved up, maintaining a flow of water over the gills.

Question 22

Describe the adaptations that make the bony fish gas exchange system an efficient exchange surface.

Answer 22

1. The tips of adjacent gill filaments overlap- increases resistance to the flow of water over the gill surfaces and slows the movement of water- more time for gaseous exchange.
2. Countercurrent exchange system

Question 23

Define countercurrent exchange system and explain why it is important

Answer 23

1. The water moving over the gills and the blood in the gill filaments flow in different directions.
2. A steep conc gradient is needed for fast efficient diffusion.
3. Because they flow in opposite directions, a countercurrent exchange system is set up.
4. This ensures a steeper concentration gradients are maintained than if they flowed in the same direction.- the water most depleted in oxygen is put next to blood with no oxygen- still conc gradient
5. This results in more gaseous exchange can take place.
6. Bony fish remove around 80% oxygen, cartilaginous fish have parallel systems and can only extract 50%.

Question 24

Define parallel exchange system

Answer 24

A system where both the water and blood flow in the same direction.

Question 25

Draw a diagram to show how a much higher oxygen saturation of the blood can be achieved by a countercurrent exchange system as compared to a parallel exchange system.

Answer 25

1. Draw two graphs with distance along gill plate as x-axis and % saturation of oxygen as y.
2. For counter current there are two parallel line next to each other but with arrows the opposite way
3. For parallel two curved arrows which start at opposite ends of the y axis and then pull together and almost meet .

Question 26

Label and annotate photographs and drawings of a dissection of the gaseous exchange system of a bony fish.

Answer 26

Look at diagrams and memorise

Question 27

Label and annotate photographs and drawings of a dissection of the gaseous exchange system of an insect.

Answer 27

Look at diagrams and memorise

Question 28

Label (and annotate with adaptations for gas exchange) photomicrographs of alveolar tissue, tracheae and tracheoles of insects, and gill filaments and lamellae of bony fish.

Answer 28

1. Look in textbook at examples of what they look like

Question 29

Describe the features of a gas exchange system that become apparent under microscopic examination that aren’t easily seen when observing the whole organ system.

Answer 29

1. The part of the system which improves surface area e.g. lamellae in fish- because they are usually very small projections so can’t be easily seen
2. You can’t see short diffusion distance