Gaseous Exchange In Bony Fish And Insects

Question 1

What are bony fish

Answer 1

A large group of fish which have evolved a skeleton made out of bone.

Question 2

What are the features of bony fish

Answer 2

They are large active organisms with a very high oxygen requirement, and because of their large size they have a very low SA:VOL ratio.

Question 3

What is a feature of the scales of fish

Answer 3

It doesn’t allow gases to pass through

Question 4

Where do fish get their oxygen from, what is a feature of the source of oxygen and what have fish evolved as a result

Answer 4

They get their oxygen from the water, however the concentration of oxygen in the water is much lower than in air, and as a result bony fish have evolved a specialised gas exchange system, extracting the maximum amount of oxygen from water.

Question 5

What is the operculum

Answer 5

A flap of tissue on either side, slightly behind the head that covers the gills.

Question 6

What is behind the operculum and what is inside this cavity

Answer 6

Behind the operculum is the opercular cavity and inside the opercular cavity are the gills.

Question 7

What is the path that the oxygen takes from the water to the fish

Answer 7

Oxygen rich water enters the fish through the mouth, the water then passes over the gills, in the gills oxygen diffuses from the water into the blood and CO2 diffuses from the blood into the water, water then passes out through the opercular opening.

Question 8

What do gills consist of

Answer 8

They consist of several bony gil arches,

Question 9

What extends from the gill arches

Answer 9

Extending from the gill apaches are a large number of gill filaments. Many pairs of gill filaments extend from each arch.

Question 10

What are the gill filaments covered with and what occurs there

Answer 10

Numerous gill lamellae (sometimes called gill plates) and this is where gas exchange takes place.

Question 11

What occurs when water passes through the gil lamellae

Answer 11

Water flows in between the gill lamellae and oxygen diffuses from the water into the bloodstream and CO2 from the bloodstream into the water

Question 12

What are the gill lamellae adapted for

Answer 12

Efficient diffusion of gases

Question 13

What are some adaptations of the gill lamellae (1)

Answer 13

They have a massive surface area for gases to diffuse over
Very short diffusion distance through the walls of the lamellae and the bloodstream.

Question 14

What are some adaptations of the gill lamellae (2)

Answer 14

The gill lamellae have an extensive network of blood capillaries maintaining steep concentration gradients
The tips of the lamellae overlap increasing resistance to the flow of water over the gills and slows down the movement of water. Allowing more time for gaseous exchange to take place.

Question 15

What occurs in the counter current exchange system

Answer 15

Blood with a low concentration of oxygen passes into the capillaries of the gill lamellae.
As the blood passes through the gill lamellae oxygen diffuses from the water into the bloodstream
Oxygen rich blood then passes out of the gill lamellae and leaves the gills.

Question 16

What is a feature of a counter current exchange system

Answer 16

The flow of blood is in the opposite direction to the flow of water
The system always maintains a steep concentration gradient for oxygen

Question 17

What occurs in parallel flow exchange systems

Answer 17

The blood and water travel in the same direction.

This means that there will be a very high rate of diffusion at the beginning however, after a short distance the concentration of oxygen in the blood and water will be the same (equilibrium) and diffusion stops.

Question 18

What is a feature of a parallel flow exchange system

Answer 18

No more than 50% of the available oxygen in the water can diffuse into the bloodstream.

Question 19

What occurs to do with diffusion in a counter current flow

Answer 19

Equilibrium is never reached and diffusion of oxygen occurs across the entire length of the lamellae. So around 80% pod the oxygen in the water diffuses into the bloodstream.

Question 20

What is the flow of water over the mouth and gills caused by in non bony fish

Answer 20

It is caused by the fish swimming forward.

Question 21

What have bony fish evolved

Answer 21

A different mechanism allowing water flow to occur even when the fish is not swimming.

Question 22

What is the process allowing water to flow over the mouth and gills when the fish isn’t moving (1)

Answer 22

When a bony fish opens its mouth water flows into the buccal cavity, the floor of the buccal cavity drops down increasing the volume available for water.
The fish shuts the operculum which increases the volume of the opercular cavity which contains the gills.
Due to the increased volume the pressure in the opercular cavity falls.

Question 23

What is the process allowing water to flow over the mouth and gills when the fish isn’t moving (2)

Answer 23

At the same time the floor of the buccal cavity lifts upwards increasing the pressure of the water causing the water to flow over the gills in the opercular cavity.

Now the fish closes its mouth and opens the operculum and at the same time the sides of the operculum cavity squeeze inwards on the water.

Increasing the pressure of the water forcing it out the operculum.

Question 24

What type of organisms are insects

Answer 24

They are very active organisms with a very high oxygen demand

Question 25

In insects what has the gas exchange system evolved to do

Answer 25

Provide oxygen directly to the cells

Question 26

What do insects have a specialised transport system for and what do they not have one for

Answer 26

They have a specialised transport system to transfer nutrients not oxygen

Question 27

What are insects covered with and what does this mean

Answer 27

Insects are covered with a protective exoskeleton made of the polysaccharide chitin Gases such as oxygen and carbon dioxide can’t pass through the exoskeleton as it is impermeable

Question 28

What is present on the surface of the exoskeleton and what does they do

Answer 28

Spiracles, which allow gases such as oxygen and carbon dioxide to diffuse into the body of the insects

Question 29

What do spiracles lead into and where are they located and what is their diameter

Answer 29

They lead into a network of tubes called tracheae which are relatively wide with a diameter around 1mm. And they extend down and along the insect’s body’s

Question 30

What are the walls of the tracheae strengthened with and what does this do

Answer 30

Chitin and this prevents the tracheae from collapsing for example when the insect moves

Question 31

Does gaseous exchange occur in the tracheae and if not why

Answer 31

Because chitin is relatively impermeable to gases it prevents gaseous exchange in the tracheae

Question 32

What extends from the tracheae and what is there diameter.

Answer 32

Very fine tubes called tracheoles which have a diameter of 1uM or less

Question 33

What is a tracheole and what is a property of them

Answer 33

It is a single cell that has extended to form a hollow tube, and they are not supported by chitin allowing gases to diffuse through.

Question 34

How many tracheoles are in insects and where are they present

Answer 34

A huge number of them extend down in between the cells of the insect’s body

Question 35

What allows the rapid diffusion of oxygen in the tracheoles

Answer 35

The tracheoles have a narrow diameter and are very close to cells, so there is a short diffusion distances for gases moving between the cells and the tracheoles.

Question 36

Where does CO2 diffuse into in insects

Answer 36

It rapidly diffuses back into the air in the tracheoles.

Question 37

What do the large number of tracheoles do

Answer 37

They provide a very large surface area for gas exchange allowing insects to maintain a very quick rate of aerobic respiration.

Question 38

How does the oxygen diffuse into cells

Answer 38

It diffuses in the moisture in the tracheoles walls and then diffuses into cell

Question 39

What are the ends of the tracheoles filled with

Answer 39

A fluid called the tracheal fluid

Question 40

When is the tracheol fluid used

Answer 40

During intense activities cells around the tracheoles undergo anaerobic respiration producing lactic acid acid reducing the water potential of the cells. Causing the water in the tracheal fluid to move into the cells.

Question 41

When is the tracheol fluid used (2)

Answer 41

Reducing the volume of traheal fluid, drawing air down into the tracheoles. It also increases the tracheole surface area available for the diffusion of oxygen and carbon dioxide.

Question 42

What sort of process is diffusion in most insects

Answer 42

It is a passive process where oxygen diffuses down its concentration gradient form the high concentration in the external air, into the tracheoles where the concentration is lower. And CO2 diffuses in the opposite way.

Question 43

Why are insects small

Answer 43

The rate of diffusion increases with distance, so they tend to be small reducing the distances required for diffusion to take place.

Question 44

What is a significant problem that insects face

Answer 44

water loss as the wells of the tracheoles are moist and the ends of the tracheoles contain tracheal fluid. So water vapour can diffuse out of an insect by the spiracles.

Question 45

What do insects have to mitigate water loss

Answer 45

Each spiracle is surrounded by a muscular sphincter, allowing insects to reduce water loss by closing their spiracles. For example when an insects oxygen demand is very low.

Question 46

What are the 3 main body segments of insects

Answer 46

The head, the thorax and the abdomen

Question 47

What can some insects do (volume)

Answer 47

Contract muscles to change the volume fo the thorax and the abdomen Causing pressure changes in the tracheae and the tracheoles pushing air in and out. This bulk transport of air is called mass transport.

Question 48

What do some insects have (expanded)

Answer 48

Contain expanded sections called air sacs, changes in the volume of the thorax and abdomen can squeeze the air secs causing air to move form the air secs into the tracheoles.

Question 49

What can the air sacs also do

Answer 49

They can also use the air in the air sacs when the spiracles have been closed for water conservation.