LESSON 5: THE GAS EXCHANGE IN PLANT AND ANIMALS

• Gas exchange


  The process of absorbing inhaled atmospheric oxygen molecules into the bloodstream and offloading carbon dioxide from the bloodstream into the atmosphere
• Gas exchange in organisms

  • Constantly delivers oxygen molecules to cells, aiding in the oxidation of carbohydrates
  • Assists in the elimination of carbon dioxide molecules as a result of cellular respiration
  • Movement of gases depends on the relative differences in the pressures of gases
  • Involves a diversity of structures in organisms that allows for an efficient exchange of gases
• Gas exchange in plants

  • Supports the cellular respiration by providing a continuous supply of oxygen and also supports cellular photosynthesis by providing a continuous supply of carbon dioxide
  • Occurs through diverse structures such as stomata, root hairs, and lenticels, rather than being facilitated by a single organ system dedicated to gas exchange
• Cuticle


  A waxy layer that covers the leaves of all plant species and reduces the rate of water loss from the leaf surface
• Upper epidermis


  A single layer of cells found directly below the cuticle on the top of the leaf
• Lower epidermis


  Another single layer of parenchyma cells, but several stomata (flanked by guard cells) are visible in this epidermal layer
• Palisade mesophyll


  Tightly packed cells that contain chloroplasts to maximize energy production during photosynthesis
• Spongy mesophyll


  Loosely packed cells with large air spaces between them
• Guard cells


  Control the opening and closing of stomata
• Stomata


  Tiny openings present on the epidermis of leaves
• Root hairs


  • Absorb the dissolved oxygen in water to breathe and exchange gases to and from tiny air pockets present in between soil particles
• Pneumatophores


  Modified roots in mangrove species that allow them to adapt to waterlogged soil conditions
• Lenticels


  Small pores on the bark of woody stems and roots that allow for the exchange of gases such as oxygen and carbon dioxide between the plant and its surroundings
• Aerenchyma


  Structures that allow plants to efficiently exchange gases underwater, where the availability of oxygen can be limited
• Gas exchange is essential for plants as it helps them carry out photosynthesis, which is the process of producing food and energy from light, water, and carbon dioxide
• Gas exchange in animals

  The process where different gases (oxygen and carbon dioxide) get exchanged/transferred/swapped in opposite directions
• Sources of oxygen for animals

  • Water
  • Air
• Diffusion


  The spontaneous movement of gases, without the use of any energy or effort by the body, between the alveoli and the capillaries in the lungs. It is a process in which material travels from regions of high concentration to low concentration until equilibrium is reached.
• Skin as a respiratory surface

  • It must have mucus glands
  • It must be thin
  • It must be supplied with a dense network of capillaries
• Gills


  Thin tissue filaments that are highly branched and folded, allowing for the efficient exchange of gases when water passes over them
• Parts of gills


  • Gill arch
  • Gill rakers
  • Gill filaments
  • Gill lamellae
• Aside from respiration through the skin, amphibians also use lungs and gills
• Tracheal system


  A network of small tubes that carries oxygen to the entire body, the most direct and efficient respiratory system in active animals, with tubes made of a polymeric material called chitin
• Parts of tracheal system

  • Trachea
  • Air sacs
  • Spiracles
• Lungs


  • A very efficient adaptation for gas exchange for higher forms of animals, addressing the main factors that affect the rate of diffusion
• Lung systems


  • Amphibian
  • Reptilian
  • Mammalian
  • Aves
• Pulmonary ventilation in mammals

  Takes place through the help of the contraction and relaxation of the diaphragm, a large dome-shaped muscle just beneath the lungs
• Carbon dioxide concentration in the blood is higher than in the alveoli


  Carbon dioxide will move from the blood into the alveoli
• Inhalation


  The diaphragm contracts (moves down), the intercostal muscles contract (stretch out), causing the rib cage to move up and the chest to expand
• Exhalation


  The diaphragm relaxes (becomes dome-shaped), causing the intercostal muscles to relax
• Gas exchange is a very important process for life, as it ensures that animals are able to use the oxygen they breathe in from the atmosphere, and allows them to exhale the waste product carbon dioxide
• 
  

  Oxygen will diffuse into the moist membrane of the alveolar wall and into the blood