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OCR A-level Biology > Exchange Surfaces and Breathing > Flashcards

Flashcards in Exchange Surfaces and Breathing Deck (26)
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Why do organisms need exchange surfaces?

The sa:v ratio is too low to allow basic diffusion


Why does level of activity affect if an organism needs an exchange surface or not?

More metabolically active organisms will require exchange surfaces so that they can perform more respiration to produce more ATP


What are the 3 features of a good exchange system?

Large SA:V ratio

Short diffusion pathway

Good Blood supply


Why is a good blood supply important for diffusion?

Provides working areas with Oxygen for respiration

Removes molecules that are being diffused to maintain a steep concentration gradient


What are the parts features of the mammalian exchange system?



What is the role of the intercostals?

Move the lungs up and down during breathing

To work with the diaphragm to create pressure gradients to cause breathing


How are the alveoli specialised to perform their function?

Large SA:V ratio

Moist surface, allows gasses to diffuse easier and prevents pneumothorax

Short diffusion pathway (only 1 cell thick)

Good blood supply - transports CO2 to the lungs and O2 away from the lungs


What do alveoli's walls contain?

Elastic fibres

Stretch during inspiration and recoil in expiration to push air out


How are the airways specialised to perform their function?

Have wide lumen to allow sufficient airflow without obstruction

Are lined with ciliated epithelium and goblet cells. Goblet cells release mucus to trap pathogens , epithelium move this up to the top of the airway where it is swallowed

Supported by rings of cartilage to prevent collapse during inspiration when pressure is low


What is the role of smooth muscle and elastic fibres in the airways?

Smooth muscle can contract to restrict airflow, useful if there is something harmful in the air

Cannot relax on its own requires elastic fibres

Smooth muscle may over contract during anaphylaxis


What device measures lung volumes?



What are the 2 components of lung volume?

Vital capacity
Residual volume


What is Vital capacity?

The maximum volume of air expelled from the lungs in one breath


What are factors affecting the vital capacity of people?

How much they exercise


What is the residual volume?

The amount of air that cant be expelled and remains in the lungs


What is tidal volume?

The volume of air expelled in one breath at rest


How does a spirometer measure oxygen uptake?

A person breaths in the oxygen and the body absorbs some of it

They breathe out carbon dioxide which is absorbed by the soda lime

The difference in volume is the amount of oxygen uptake


How would you oxygen uptake from a spirometer trace?

Draw a line from one trough to another trough

Measure the gradient of the line


How would you measure the breathing rate from a spirometer trace?

Count the number of peaks in a minute


Describe the structure of the gaseous exchange system in bony fish

Gills covered by a bony plate called the operculum

Each gill consists of two rows of filaments which are very thin

Gill filament surface is folded into lamellae

Capillaries carry deoxygenated blood close to the surface of lamellae to perform gaseous exchange


What is a countercurrent flow in the gills?

Blood flows in the opposite direction as the water

Maintains a steep concentration gradient and allows most oxygen to be removed


What is the buccal cavity?

The mouth of the fish


How does the buccal-opercular pump work?

Buccal cavity floor moves down drawing water into it

Mouth closes and floor is raised pushing water through the gills

simultaneously the operculum moves outwards to draw water over the gills also


What is the name of the fluid circulated around insects?



Describe the gaseous exchange system in insects?

Have a respiratory cavity where gaseous exchange occurs

Air enters through a spiracle

transported via tracheae and tracheoles

The end of the tracheoles contain tracheal fluid where gaseous exchange occurs


Give examples of how different insects may ventilate?

Sections of the tracheal system have flexible walls that can be contracted and relaxed by the flight muscles

Movement of the wings can alter the volume of the thorax causing pressure changes and thus ventilation

Some use valves over spiracles to create a ventilation system where air is drawn in at the front and out at the back