Animals have different respiratory structures depending
mainly on the environment they live. So , we can study various type of
respiratory structures in animals. the
area where gaseous exchange takes place with the environment is called the
respiratory surface. An effective respiratory surface must have the following
properties.
• It must be
permeable, and wet so that gases can pass through
• It must be thin
because diffusion is only efficient over the thin surfaces.
• It should possess
a large surface area to allow sufficient
volumes of gases to be
exchanged
according to the organism’s need.
• It should possess a good blood supply.
Diffusion and surface to volume ratio
Respiratory gas exchange
occurs due to diffusion. In small animals diffusion through
body surface is adequate as they are simple and the energy requirement
is very low.
However, when surface volume ratio decreases, sufficient area is needed
for gas
exchange and thus respiratory structures with large surface area were
developed.
Respiratory structures in animals
• Body surface e.g.,
Earthworm, flat worm
• External gills e.g.,
Polycheate worms, Arenicola tadpole of frog, salamander
• Internal gills e.g.,
Bony fish, lobster
• Trachea eg:
Insects, Millipedes, Centipedes
• Book lungs e.g.,
Spider, scorpion
• Lungs e.g.,
Human, Reptiles, Birds
