gas exchange

• how do gases enter single-celled organisms

  they diffuse through their cell membrane
• what happens to sa:v ratio as the size of an organism increases

  sa:v ratio decreases
• state the name of the small tubes that are used to transport gases in the insect exchange system

  tracheoles
• what are spiracles

  small holes in the thorax and abdomen of insects which allow gases to diffuse into the tracheoles
• what is the name for the small folds on the surface of fish gills

  lamellae
• state three adaptations of gills for efficient gas exchange

  1. highly folded
  2. lamellae increase surface area
  3. counter-current flow
• where is the site of gas exchange in plants?

  mesophyll cells
• how do gases diffuse into plants?

  through the stomata
• what state do the guard cells have to be in to allow the stomata to open?

  the guard cells must swell with water
• how do hairs around an insect's spiracles help to prevent water loss?

  they decrease the concentration gradient between inside the trachea and the environment
• other than spiracles, state one component of an insect which prevents water loss

  a waxy cuticle which is waterproof
• what is the name of a plant specialised due to living in a dry environment

  xerophytic
• state four features of xerophytic plants that help to prevent water loss

  1. fewer stomata
  2. sunken stomata
  3. fine hairs on the epidermis
  4. waxy cuticle
• state the steps in the passage of oxygen through the human gas exchange system

  1. trachea
  2. bronchi
  3. bronchioles
  4. alveoli
• state three components of the human body which impact ventilation

  • bones in the ribcage
  • intercostal muscles
  • diaphragm
• state three ways that alveoli are specialised for efficient gas exchange

  • they are surrounded by a large network of capillaries (large surface area)
  • made of a thin layer of cells (short diffusion pathway)
  • good blood supply (steep concentration gradient)
• describe what happens during inspiration

  • diaphragm contracts and moves down
  • ribcage moves up and out
  • internal intercostal muscles relax
  • external intercostal muscles contract
  • thoracic cavity pressure decreases
  • thoracic cavity volume increases
• describe what happens during exhalation

  • diaphragm relaxes and moves upwards
  • ribcage moves down and in
  • external intercostal muscles relax
  • internal intercostal muscles contract
  • thoracic cavity pressure increases
  • thoracic cavity volume decreases
• define tidal volume

  the volume of air inspired/expired per breath
• define ventilation rate

  the number of breaths someone takes per minute
• state the equation for ventilation rate

  ventilation rate = tidal volume x breathing rate