Gas Exchange and Circulation

• Gas Exchange

  often called respiratory exchange or respiration
• Gas Exchange in Plants

  the process whereby water vapor and oxygen leaves, and CO2 enters
• Gas Exchange in Animals

  uptake of molecular oxygen from the environment and the discharge of CO2 to the environment
• Structures in gas exchange for plants

  • Stomata (leaves)
  • Lenticels (stems and roots)
  • Pneumatophores or the lateral roots of mangroves (specialized)
• Not all plants have pneumatophores.
• Stomata - pores in the leaves that have parenchyma cells which serve as guard cells.
• Stomata


  open and close to allow the intake of CO2 and release of oxygen
• Lenticels - are pores found on the epidermis of plants that always remain open.
• • stomata (entry and exit)
  • lenticels (remains open)
  • pneumatophores (grows upward)
• Lenticels

  permit the exchange of gases between the environment and the internal tissue spaces of the organs
• Respiratory Surfaces in Animals

  • outer surface
  • skin
  • gills
  • lungs
  • tracheae
  • air sacs
• Gas exchange across respiratory surfaces takes place by diffusion.
• Animals require large, moist respiratory surfaces.
• Pneumatophores

  site of oxygen intake
• worms - cutaneous

  marine - gills

  insects - tracheal system

  birds - air sacs

  mammals - lungs
• Birds have 9 air sacs
• Through body surfaces

  cutaneous respiration or skin breathing
• Cutaneous respiration occurs mostly in protists.
• Through body surfaces

  air or water through the moist surface directly into the body
• Through body surfaces (examples)

  amoeba and flatworm
• Gills

  outfoldings of the body that create a large surface area for gas exchange.
• Gills

  • paramodium

  • crayfish

  • fish gills

  • anuran amphibian
• Polychaetes (marine worms) have a pair of flattened appendages called parapodia on each body segment.
• Parapodia serves as gills and function in crawling and swimming.
• Crayfish - long, feathery vills covered by the exoskeleton (ex. crayfish and lobster)
• Fish use a countercurrent exhange system, where blood flows in opposite direction to water passing over the cells.
• Anuran amphibian

  external gills on each side of the head provide the axolotl with oxygen and its signature look
• Axolotl is also known as Mexican walking fish
• Tracheal system for insects

  consists of tiny branching tubes that penetrate the body
• Tracheal system for insects

  supply O2 directly to body cells
• Air sacs


  serve as internal compartments which hold air and facilitate internal air passage to allow birds to have continuous flow of oxygen
• Lungs


  an infolding of the body surfaces
• Air passes through the pharynx, larynx, trachea, bronchi, bronchioles to the alveoli, where gas exchange occurs.
• Circulation in Plants

  • Transpiration (xylem - water/solutes)
  • Translocation (phloem - sucrose, glucose, amino acids)
• Transpiration occurs in xylem
• Translocation occurs in phloem
• Transpiration in Plants

  the evaporation of water from the roots to the stem of the plant throught osmosis in the stomata
• Translocation in Plants

  the transport of glucose, sucrose, and amino acids (nutrients) throughout the plant
• Translocation in plants takes place via active transport then absorbed by the roots.
• xylem

  functions in the conduction of water and dissolved minerals