Diversity of respiratory structures in the animal kingdom.

• The area where gaseous exchange takes place with the environment is called the respiratory surface.
• Gaseous exchange takes place in all organisms by the physical process of diffusion. So the respiratory surfaces must have the following properties.

1. It must be permeable to respiratory gases such as oxygen and carbon dioxide.
2. It must be moist/wet. Because dissolved oxygen will diffuse through the respiratory surface.
3. It must be thin, short distance, therefore diffusion will be efficient.
4. It must possess a large area to allow sufficient volume gases to be exchanged according to organisms need.
5. It should possess good supply of blood .because blood will remove oxygen from the respiratory surface thus maintaining oxygen concentration gradient.

 

• There is a huge diversity in respiratory organs in the animal kingdom.
• Organisms require oxygen either direct from the atmosphere or from the dissolved O₂ in water.
• There are number of differences in the O₂ content in the air and water.
  • Atmosphere-21%
  • Water-0.8%

• Cell membrane
  • Amoeba
• Exernal gills
  • Polychaete
  • Tadpole of frog
  • Salamander
  • Arenicola
• Internal gills
  • Bony fish
  • Lobster
• Trachea
  • Insects
  • Millepedes
  • Centipedes
• Book lungs
  • Spiders
  • Scorpian
• Lungs
  • Human
  • Reptiles
  • Birds
• Epidermal gill
  • Earthworm
  • Flat worms
  • Taenia

 

• They exchange gases through diffusion.
• Respiratory surface is the cell surface membrane.
• Metabolism is low, the O₂ consumption is low.
• Therefore surface area / Volume ratio is high.
• Diversity of microorganisms in relation to oxygen is as;
  • Aerobic
  • Anaerobic
  • Facultative
  • Micro aerophilic

 

• There are no special organs designed for gas exchange in earth worms.
• Gas exchange takes place through diffusion over the whole body surface.
• They possess a blood vascular system
• Blood contains the respiratory pigments.

 

Pumping activity by major blood vessels and the dissolved gases around the body exchange through diffusion.

• In insects gaseous exchange occurs by means of a system of tube called tracheal system.
• This system allows O₂ to diffuse from outside air directly to the tissues or cells.
• Pairs of holes called spiracles found on the segments and these further branch as trachea up to tissues.
• Its trachea secretes a thin layer of small supporting material around its outer surface.
• At the end they are filled with watery fluid.

 

• Fish possesses gill filaments in the pharyngeal region or the region between the buccal cavity and oesophagus
• In bony fishes there are 04 pairs of gill arches.
• Each gill is made of two pairs of gill filaments arranged in the shape of “V” .
• The gill filament possesses gill lamella, thin plate which have a rich supply of blood capillary (To increase its surface area)
• The rate of absorption is increased by “counter current system”- transportation of water in the opposite direction of the blood flow.