adaptation for gas exchange in animals unit 2

The organisms volume

The surface area of organism

The surface adapted for use for gas exchange
The level of activity of the organism

Their SA:V ratio gets lower- specialised respiratory surfaces are needed

Because they are covered in an impermeable cuticle (chitin) to reduce water loss by evaporation

Thoracic spiracles open, abdominal closed
Abdomen expands
Decrease in pressure which pulls air in thru thoracic spiracles
(opposite for ventilation out)

Holes in the exoskeleton that open and close
Thoracic and abdominal spiracles
Lead to tracheae

Connected to spiracles
System of chitin lined tubes- supports and stops from collapsing
Lead to tracheoles

The gas exchange surface
Close to the cells of insect
Oxygen diffuses toward cells, CO2 diffuses away from cells (conc gradient)
Fluid-filled at rest

Insect respiratory system

Highly active tissue
Contains many mitochondria for oxygen in aerobic respiration and ATP for muscle contrctin

•Aerobic respiration uses oxygen for ATP, oxygen conc drops
•Fluid-filled tracheole diffuses oxygen into muscle-causing conc gradient
•Anaerobic resp produce lactic acjd which lowers WP
•Causes H2O to leave tracheloes thru osmosis containing dissolved oxygen
•Higher SA for oxygen to diffuse

Fluid in tracheoles decrease to shorten diffusion path
Whole body contractions ventilate tracheal system by speeding up airflow thru spiracles

Smaller SA:V ratio
Have high metabolic rates due to high activity- oxygen reqments high
Need to maintain conc gradient for gas exchange with ventilation mechanism

To push water (low oxygen content) over the high SA gill filaments

Gill filaments collapse, stick together and gas exchange surface becomes too small for survival

•Mouth opens, buccal cavity floor lowers- Vol increase, pressure decrease
•Water goes in
•Mouth closes, buccal cavity floor rises- increases pressure which pushes water over gills
•Water goes into opercular cavity- buccal pressure decreases, opercular pressure increases
•Operculum opens and water moves out

Gill filaments, made out of gill plates/lamellae

The gill rakers

Thin- short diffusion pathway
Moist (terrestrial animals)
Large SA
Permeable to gases
Good blood supply to maintain conc gradients (large animals only)

Water and blood flow in same direction
Equilibrium is reached, oxygen diffusion reaches 0 net movement halfway across gill plate

Water and blood flow in opposite directions across gill plate
Conc gradient is maintained, oxygen diffuses into blood across entire gill plate

Counter current flow

Concurrent/continuous flow

Single celled organism
Large SA:V ratio
Short diffusion distance to middle of cell
Low metabolic rate-oxygen demand low

Muticellular organism
Smaller SA:V ratio than amoeba
Flattened and long body to reduce diffusion pathway, sufficiently gains oxygen

Multicellular
Even smaller SA:V ratio than both amoeba and flatworm.
Body surface is used for gas exchange but circulatory system needed to distribute oxygen.
Blood vessels close to skin surface- blood has haemoglobin with high affinity for oxygen.
Mucus secreted to moisten surface, slow moving to reduce O demand.

Intercostal muscles contract, ribcage goes up and out
Outer pleural membrane pulled out- pressure reduced..
..Inner p membrane pulled out
Pulls on lungs surface- increase in volume of alveoli
Alveolar pressure goes below atmospheric pressure and air pulled in

Have aquatic tadpoles- have feathery gills
Dont ventilate same as fish but movement of water over gills maintains conc gradient

Soft
Moist
Gas exchange surface at rest

Closed system
Oxygen and CO2 circulate in haemoglobin

Movements of buccal cavity ventilate lungs
Lungs are simple with a few alveoli