Exchange surfaces- Insect and Fish gas exchange Flashcards
Define the term exoskeleton
An external skeleton of some organisms- made of chitin and is waterproofed to reduce water loss.
Define the term spiracle
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.
Define the term trachea
The main airway, supported by incomplete rings of cartilage, which carries warm moist air down form the nasal cavity into the chest.
Define the term tracheoles
A small pipe that branches of a trachea in insects and is used for gas exchange.
Define the term tracheal fluid
Fluid found at the ends of the tracheoles in insects that helps control the surface area available for gas exchange and water loss.
Outline the structure of the insect gas exchange system and describe the way oxygen reaches the body cells.
- Air moves into the tracheae through pores on the surface called spiracles.
- O2 travels down the conc gradient towards the cells.
- CO2 from the cells moves down its own conc gradient towards the spiracles to be released into atomsphere.
- 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
- The oxygen then diffuses from this fluid into body cells- CO2 diffuses in the opposite direction.
Explain why insects will tend to keep spiracles closed when oxygen demands are very low.
Spiracles can be opened and closed by sphincters- the spiracle sphincters are kept close as much as possible to minimise water loss.
Describe the adaptations of the insect gas exchange system that make it an efficient exchange surface.
- 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
Describe how activity changes the volume of tracheal fluid in the tracheoles, and explain the value of this occurring.
- 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.
Describe two adaptations that insects with very high energy demands have to increase the efficiency of their gas exchange system.
- 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.
- 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.
Describe the advantages of, and challenges faced by, gas exchange systems operating in water rather than air.
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.
Define the term opperculum
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.
Define the term buccal cavity
The space behind the mouth in a fish.
Define the term opercular valve
The flap that allows the oppeculum to be moves outwards whilst keeping it closed
Define the term gill arch
The bony structure that supports the gill filaments,
Define the term gill filament
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
Define the term gill plates
Gill plates are large stacks of gill filaments
Define the term gill lamellae or plates
Raised plates on the surface of gill filaments which in total create a large SA for gas exchange
Label and annotate a diagram showing the features of the gas exchange system in bony fish.
Find an online labelling diagram
Describe the mechanism of inspiration in bony fish.
- Mouth opens and floor of buccal cavity is lowered
- Expansion of buccal cavity increases the volume and reduces pressure causing water to enter via the mouth (buccal cavity pressure pump)
- At the same time the opercular valve is shut and the opercular cavity containing the gill expands
- This lowers the pressure in the opercular cavity containing the gills.
- 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
Describe the mechanism of expiration in bony fish.
- Mouth closes, the operculum opens and the side of the opercular cavity move inwards.
- These actions increase the pressure in the opercular cavity and force water over the gills and out of the operculum.
- The floor of the buccal cavity is steadily moved up, maintaining a flow of water over the gills.
Describe the adaptations that make the bony fish gas exchange system an efficient exchange surface.
- 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.
- Countercurrent exchange system
Define countercurrent exchange system and explain why it is important
- The water moving over the gills and the blood in the gill filaments flow in different directions.
- A steep conc gradient is needed for fast efficient diffusion.
- Because they flow in opposite directions, a countercurrent exchange system is set up.
- 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
- This results in more gaseous exchange can take place.
- Bony fish remove around 80% oxygen, cartilaginous fish have parallel systems and can only extract 50%.
Define parallel exchange system
A system where both the water and blood flow in the same direction.
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.
- Draw two graphs with distance along gill plate as x-axis and % saturation of oxygen as y.
- For counter current there are two parallel line next to each other but with arrows the opposite way
- For parallel two curved arrows which start at opposite ends of the y axis and then pull together and almost meet .
Label and annotate photographs and drawings of a dissection of the gaseous exchange system of a bony fish.
Look at diagrams and memorise
Label and annotate photographs and drawings of a dissection of the gaseous exchange system of an insect.
Look at diagrams and memorise
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.
- Look in textbook at examples of what they look like
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.
- 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
- You can’t see short diffusion distance
