7.4 Ventilation and gas exchange in other organisms

Where do insects mainly dwell?

mainly land-dwelling animals

What are insects’ oxygen requirements like?

relatively high

What feature covers insects?

tough exoskeleton

What can’t take place through this tough exoskeleton?

little or no gaseous exchange can take place

When are many insects very active?

during parts of their life cycles

What don’t insects have that can carry oxygen?

don’t usually have blood pigments that can carry oxygen

Due to having no oxygen-carrying blood pigments and not being able to exchange gases through their surface, what do insects need a different way of doing?

a different way of exchanging gases

What has the gaseous exchange system of insects evolved to do?

to deliver the oxygen directly to the cells and to remove the carbon dioxide the same way

Gas exchange in insects: what are spiracles?

small openings along insects’ thorax and abdomen

Gas exchange in insects: what enters and leaves the system through the spiracles?

air

Gas exchange in insects: what else is lost through the spiracles?

water

Gas exchange in insects: just like mammals, what do insects need to maximise but also what do they need to minimise at the same time?

need to maximise the efficiency of gaseous exchange, but minimise the loss of water

Gas exchange in insects: what can spiracles be opened or closed by in many organisms?

by sphincters

Gas exchange in insects: why are the spiracle sphincters kept closed as much as possible?

minimise the loss of water

Gas exchange in insects: when will all the spiracles be closed most of the time?

when an insect is inactive and oxygen demands are very low

Gas exchange in insects: when do more of the spiracles open?

when the oxygen demand is raised or the carbon dioxide levels build up

Gas exchange in insects: what are the largest tubes of the insect respiratory system?

tracheae

Gas exchange in insects: Where are the trachea located?

running both into and along the body of the insect - leading away from the spiracles

Gas exchange in insects: what is the diameter of the trachea?

up to 1mm

Gas exchange in insects: what does the trachea carry?

oxygen into the body

Gas exchange in insects: what are the tracheae tubes lined by?

spirals of chitin

Gas exchange in insects: what does these spirals of chitin do for the trachea?

keeps them open if they are bent or pressed

Gas exchange in insects: what material makes up the cuticle of the trachea?

chitin

Gas exchange in insects: why does little gaseous exchange take place in the trachea?

chitin (which makes up the cuticle) is relatively impermeable to gases

Gas exchange in insects: what do the tracheae branch to form?

narrower tubes

Gas exchange in insects: what do these narrower tubes divide into?

tracheoles

Gas exchange in insects: the diameter of the tracheole tubes?

0.6-0.8µm - minute tubes

Gas exchange in insects: the structure of each tracheole?

a single, greatly elongated cell

Gas exchange in insects: why are the tracheole tubes freely permeable to gases?

no chitin lining

Gas exchange in insects: where are the tracheoles located (due to their very small size)?

spread throughout the tissues of the insect, running between individual cells

Gas exchange in insects: what takes place in the tracheoles that are spread throughout the tissues of the insect, running between individual cells?

where most of the gaseous exchange takes place between the air and the respiring cells

Gas exchange in insects: for most insects how does air move along the tracheae and tracheoles?

by diffusion alone

Gas exchange in insects: what does the vast numbers of tiny tracheoles give for gaseous exchange?

a very large surface area

Gas exchange in insects: what does oxygen dissolve in?

moisture on the walls of the tracheoles

Gas exchange in insects: what does this oxygen then diffuse into?

the surrounding cells

Gas exchange in insects: what is found near the end of the tracheoles?

tracheal fluid

Gas exchange in insects: what does tracheal fluid do?

limits the penetration of air for diffusion

Gas exchange in insects: an example of what would cause a build up in the demand for oxygen by insects?

when an insect is flying

Gas exchange in insects: what builds up as the oxygen demand builds (e.g. flying)?

lactic acid in the tissues

Gas exchange in insects: what does the lactic acid build up in the tissues result in?

water moving out of the tracheoles by osmosis

Gas exchange in insects: what does the water moving out of the tracheoles by osmosis do for gaseous exchange?

exposes more surface area

Gas exchange in insects: what is all the oxygen needed by the cells of an insect supplied to them by?

by the tracheal system

Gas exchange in insects: What is the extent of gas exchange in most insects controlled by?

the opening and closing of the spiracles

Gas exchange in insects: examples of insects with very high energy demands (6)?

larger beetles, locusts and grasshoppers, bees, wasps and flies

Gas exchange in insects: what do these insects with very high energy demands have to supply the extra oxygen needed?

alternative methods of increasing the level of gaseous exchange

Gas exchange in insects: the 2 alternative methods of increasing the level of gaseous exchange (for insects that require more oxygen)?

mechanical ventilation of the tracheal system and collapsible enlarged tracheae or air sacs - which act as air reservoirs

(Insect) mechanical ventilation of the tracheal system: what is actively pumped into the system?

air

(Insect) mechanical ventilation of the tracheal system: how is air actively pumped into the system?

by muscular pumping movements of the thorax

(Insect) mechanical ventilation of the tracheal system: what do these movements change the volume of?

the body

(Insect) mechanical ventilation of the tracheal system: what does these movements changing the volume of the body change?

the pressure in the tracheae and tracheoles

(Insect) mechanical ventilation of the tracheal system: what happens as the pressure changes?

air is drawn into the tracheae and tracheoles, or forced out

(Insect) collapsible enlarged tracheae or air sacs: what do they act as?

air reservoirs

(Insect) collapsible enlarged tracheae or air sacs: what are they used to increase the amount of?

air moved through the gas exchange system

(Insect) collapsible enlarged tracheae or air sacs: what are they usually inflated and deflated by?

the ventilating movements of the thorax and abdomen

Respiratory systems in bony fish: what do animals that get their oxygen from water not need to try and prevent (that land animals do) from their gaseous exchange surfaces?

don’t need to try and prevent water loss from their gaseous exchange surfaces

Respiratory systems in bony fish: How many times denser is water than than air?

1000 times denser than air

Respiratory systems in bony fish: how many times more viscous is water than air?

100 times more viscous than air

Respiratory systems in bony fish: does air or water have a lower oxygen content?

water has a much lower oxygen content than air

Respiratory systems in bony fish: why have fish evolved very specialised respiratory systems (that are different from those land-dwelling animals?

to cope with the viscosity of water and the slow rate of oxygen diffusuion

Respiratory systems in bony fish: why is moving water in one direction the simplest and most economical (in energy terms) way of gaining oxygen and respiring?

it would use up far too much energy to move dense, viscous water in and out of lung-like respiratory organs

2 examples of bony fish?

trout and cod

3 key features of the bony fish trout and cod?

relatively big, active and live almost exclusively in water

Respiratory systems in bony fish: why do bony fish's cells have a high oxygen demand?

because they are very active

Respiratory systems in bony fish: what does the size of their SA:V ratio make it impossible for bony fish to do?

supply their inner cells with the oxygen they need by diffusion alone

What feature of fishes doesn’t allow gaseous exchange?

their scaly outer covering

What is the ventilation system, that bony fish have evolved, adapted to do?

to take oxygen from the water and get rid of carbon dioxide into the water

Gills?

fish’s organs of gaseous exchange

What do bony fish maintain over the gills?

a flow of water in one direction over the gills

Adaptations of Gills that are needed for successful gaseous exchange (3)?

large surface area, good blood supply and thin layers

What are gills contained in, in bony fish?

a gill cavity

What are the gills covered by, in bony fish?

a protective operculum (protective flap)

What is the operculum also active in maintaining?

the flow of water over the gills

Diagram of a fish head and gills?

…

1?

operculum (flap that covers gills)

2?

first gill arch

Labelled diagram of a gill?

Gills: What does the bony arch do?

supports the structure of the gills

Gills: what does the efferent blood vessel do?

carries the blood leaving the gills in the opposite direction to the incoming water - maintaining a stepp concentration gradient

Gills: what does the afferent do?

brings blood into the system

Gills: How do gill filaments occur?

in large stacks - gill plates

Gills: what do gill filaments need to keep them apart?

a flow of water

Gills: why do the gill filaments need to be kept apart?

to expose the large surface area needed for gaseous exchange

Gills: what is the main site of gaseous exchange in the fish?

gill lamellae

Gills: 2 adaptations of the gill lamellae that makes it ideal for gaseous exchange?

rich blood supply and large surface area

Diagram of the arrangement of the gill stacks?

…

Why do fish need to maintain a continuous flow of water over the gills, even when they are not moving?

to allow efficient gas exchange at all times

Why is hard for gas exchange to be as efficient in water as it is in air?

diffusion is slower in water than air

How do fish keep a current of water flowing over their gills when they are swimming?

by opening their mouth and operculum

When does the flow of water over the gills stop?

when the fish stops

What kind of fish (and 2 examples) rely on continual movement to ventilate the gills?

more primitive cartilaginous fish - such as sharks and rays

What is using continual movement to ventilate the gills at all times called?

ram ventilation

What have most fish evolved that allows them to move water over their gills at all times (most don’t rely on movement-generated water flow over the gills)?

a sophisticated system involving the operculum

System fishes use to move water over their gills at all times: what is opened?

the mouth

System fishes use to move water over their gills at all times: what is lowered when the mouth opens?

the floor of the buccal cavity (mouth)

System fishes use to move water over their gills at all times: what does this opening of the mouth increase the volume of?

the buccal cavity (mouth)

System fishes use to move water over their gills at all times: what decreases as a result of this increase in volume?

pressure in the buccal cavity drops

System fishes use to move water over their gills at all times: what does this pressure drop cause?

water to move into the buccal cavity

System fishes use to move water over their gills at all times: at the same time what is shut?

the opercular valve

System fishes use to move water over their gills at all times: at the same time what expands?

the opercular cavity containing the gills

System fishes use to move water over their gills at all times: what does the expansion of the opercular cavity containing the gills lower?

its pressure