4. Gas exchange

• What is meant by metabolic rate

  Rate at which chemical reactions occur in the body
• Why do smaller animals have a higher metabolic rate

  Respire faster to replace lost heat
• Why do smaller animals have a larger SA:V

  Lose heat faster so respire more
• What is ficks law for gas exchange

  need to have a large surface area

  high concentration gradient

  thin exchange surface
• How does a singular called organism respire

  Gases diffuse through the membrane. Respiration maintains the conc gradient.
• How are fish adapted to carry out gas exchange

  large surface area - gills, many lamallae

  concentration gradient -Counter current system.

  short diffusion pathway - thin walled lamallae
• What is the counter current mechanism

  Water flows across the gill plate in the opposite direction to blood flow. Gas exchange then takes place across the whole gill as oxygen never meets equilibriu.
• How is water loss prevented in insects.

  Waxy and water proof outer layer

  spiracles can be closer

  spiracles are surrounded by small hairs
• How does gas exchange occur in insects

  Enters through spiracles and through the trachea into tracheoles and straight into the cell
• How is the gas exchange system in insects adapted to be efficient

  Have lots of tracheoles - large surface area

  thin walls - diffusion pathway
• What is abdominal pumping

  When flying more ATP is required so ventilation occurs as muscles in abdomen are contracted so forces air in and out
• How are plants adapted for water loss

  Stomata can be closed

  waxy layer
• What is the structure of the human gas exchange system

  Trachea - bronchi - bronchioles - alveoli
• What is the role of cilia and mucus

  Filter the air

  keep airways clear
• How are humans adapted for efficient gas exchange

  Millions of alveoli - SA

  only two layers of cells - thin surface

  circulation - gradient
• What happens when we breathe out

  Muscles in diaphragm relax and it returns to some shape, rib cage moves down and in so pressure increases and air is forced out
• What happens when we breathe in

  Muscles in diaphragm contract and it flattens. Ribcage moves out and up so volume increases and pressure decreases meaning air moves in
• Which muscles contract when we inspire

  Diaphragm

  external intercostal
• What is tidal volume

  Volume of air breathed in or out of the lungs in one resting breath
• Equation for pulmonary ventilation

  Tidal vol x ventilation rate