LESSON 2

• Breathing


  The physical action of taking air into the system and releasing gaseous waste
• Respiration


  The entire process of taking air into the system, exchanging needed gases for unnecessary gases, using the needed gases, and releasing the waste form of gases
• All animals must exchange gases between themselves and their environment on a continual basis
• Types of gas exchange systems

  • Integumentary exchange
  • Gills
  • Tracheal systems
  • Lungs
• Integumentary exchange


  • Occurs through the skin
  • Used by very small animals and a few larger animals that live in moist environments
• Animals that use integumentary exchange

  • Worms
• Earthworms


  • Have capillaries right under their "skin"
  • Take in oxygen from air pockets in the soil and release carbon dioxide through their outer surface
  • Must stay moist to exchange gases directly with their environment
• Cutaneous respiration/cutaneous gas exchange


  Gas exchange occurs across the skin or outer integument of an organism rather than gills or lungs
• Gills


  • Membranous filaments covered by a flap called an operculum
  • Fish open and close the flaps protecting the gills by opening and closing its mouth
  • Water enters the mouth and is forced through the gills and then out the back of the operculum
  • Oxygen diffuses into the capillaries in the gills, carbon dioxide diffuses out
• Tracheal systems


  • Air tubes that open to the outside of the body
  • Oxygen diffuses directly into the trachea, carbon dioxide exits out through the spiracles
  • Oxygen and carbon dioxide do not need to be carried through a circulatory system
• Lungs of land animals

  • Trachea branches off into bronchi, which branches off into bronchioles
  • Muscle lying underneath the lungs called the diaphragm
  • Ribs surround the chest cavity to protect the lungs and heart and assist in the motions of breathing
• Breathing process in humans

  1. Inhalation

  2. Exhalation
• Inhalation


  • Air enters through nostrils
  • Flows through nasal cavity
  • Hair, cilia, and mucus trap dust and dirt particles
  • Occasionally cough and either spit or swallow to move trapped particles out of throat
• Every cell in your body needs oxygen for its metabolic processes, so oxygen is vital to proper functioning. Without it, you die.
• Inhalation


  1. Diaphragm muscle contracts

  2. Ribcage moves upward and outward

  3. Lungs open up and air rushes in to fill the space
• Exhalation


  1. Diaphragm muscle relaxes and moves back up

  2. Ribcage moves downward and inward

  3. Pressure inside the now-smaller lungs increases, forcing air up out of the lungs

  4. Exhaled air contains carbon dioxide
• Gas exchange


  Process whereby water vapor and oxygen leave, and carbon dioxide enters plant leaves
• The gaseous balance in plants is quite complex because plant cells carry on both respiration and photosynthesis.
• All living organisms continually produce gases via metabolic and cellular activities, and the vast majority of living things are in one way or another in intimate contact with a gaseous medium.
• Plants respire in much the same way as animals; oxygen is used to oxidize carbohydrates, and carbon dioxide and water are produced as waste products.
• The photosynthetic process requires an input of carbon dioxide and water. These two reactants are used to produce carbohydrates, and oxygen is released as a waste product.
• Under normal conditions, photosynthetic rates are higher than respiration rates; thus, there is a net increase in oxygen production, accompanied by a net increase in the usage of carbon dioxide. On balance, therefore, plants use carbon dioxide and produce oxygen.
• Stomata


  Specialized openings located along the lower surface of the leaf that allow gases to move into and out of the plant
• Stomata


  • Of optimum size, shape, and distribution for the efficient diffusion of gases
• Guard cells


  Two specialized structures that surround each stoma
• Opening of stomata


  1. Guard cells take up water

  2. Expansion occurs along longitudinal axis

  3. Sides of guard cells move apart

  4. Stomate opens
• Leaf exposed to light

  Photosynthesis begins in guard cells
• Photosynthesis in guard cells

  • Residual carbon dioxide converted to carbohydrates
  • Cellular pH increases
  • Activity of enzymes converting starch and sugars to organic acids increases
  • Concentration of hydrogen ions increases
• Increased hydrogen ions in guard cells


  Exchanged for potassium ions in subsidiary cells
• Increased potassium and organic acids in guard cells

  • Lowers osmotic potential
  • Water moves from subsidiary cells into guard cells
  • Turgor pressure increases
  • Stomata open
• Gas exchange through open stomata

  1. Water vapor and oxygen exit the plant

  2. Carbon dioxide enters the plant
• Stomata close in the dark

  • Without solar energy, light-mediated photosynthesis stops
  • Carbon dioxide level increases
  • pH decreases
  • Enzymatic conversion of organic acids to sugars and starch occurs
  • Potassium ions move from guard cells to subsidiary cells
  • Osmotic potential of guard cells increases
  • Water moves out
  • Guard cells become flaccid
  • Stomata close
• Drought conditions


  Lack of water causes guard cells to lose turgor and close stomata
• High temperature


  Can cause water to leave leaf more rapidly, leading to water stress and stomatal closure
• High temperature


  Can increase cellular respiration and carbon dioxide levels, reversing carbon dioxide pressure gradient and causing stomatal closure
• Increasing humidity


  Decreases rate of water evaporation from leaf surface
• Increasing solar radiation


  Causes stomata to open faster and wider, increasing gas exchange rate
• Wind currents

  Carry water vapor away from leaf surface, reducing humidity and increasing rate of water evaporation
• Ecological impact


  The exchange of gases between living plants and the atmosphere is critical to the survival of all living organisms
• Without the release of the oxygen produced during photosynthesis, the atmosphere would contain very little of this necessary gas