Respiration Answers to Guided Reading

What Is It? The exchange of gases between an organism and its environment Gas exchange happens by diffusion across a membrane The gasses must be dissolved in water for diffusion to take place

Why Does It Need To Occur? Cells need to get the gasses into or out of the cell In our case it is the process that provides the cells with the oxygen needed to make energy and getting rid of the carbon dioxide that is made as waste Balance of gasses must be closely regulated

What Is The Main Process That Drives Respiration? DIFFUSION

What Is The Key To Efficiency In Gas-Exchange? Efficiency requires a large surface area relative to volume Exchange tissues and organs are typically covered in very small structures – this increases surface area We have alveoli in our lungs

What Is The Advantage of Respiration on Land vs. Water? Concentration of oxygen is higher in air than in water (250mL/L v. 5-10 mL/L)

What Is The Disadvantage of Respiration on Land vs. Water? Organisms on land are constantly battling the tendency to dry out With every breath, the organism loses water Also, gasses must be dissolved into water on the exchange membrane

Increased surface area = Increased evaporation (Water Loss) What Is The Issue That Land Organisms Face When They Increase Surface Area? Increased surface area = Increased evaporation (Water Loss)

How Is This Solved? Evolving gas exchange surfaces are located in an interior space – it protects the surface from excess evaporation caused by contact with the outside air and still allows a large area for exchange

What Is A Cuticle? Describe Its Purpose Cuticle = A water repellant covering on the leaves of plants Reduces water loss from the leaf surface and blocks gas exchange between the air and the cells

How Is This Advantage Present In Other Organisms? Spiracles in insects – tubes that close when levels of carbon dioxide fall below a certain point Stomata in plants – openings in the surface of the leaf that open and close to control amounts of carbon dioxide entering and water/oxygen leaving Glands in skin secrete waxes and oils to secrete protective boundaries

Water and Oxygen Carbon Dioxide

Respiratory surfaces and gas exchange Size of organism Habitat Metabolic demands Unicellular organisms Entire surface area for diffusion Simple invertebrates Sponges, cnidarians, flatworms diffusion

Gills Organisms  Fish, aquatic worms, and crustaceans Advantage  Large surface area composed of many fine, threadlike filaments Structure Description  filaments have capillaries surrounded by a thin layer of cells Mechanism  Gasses exchanged between water and the capillaries in the filaments

Skin Organisms  Worms Advantage  Direct exchange of gasses between organism and environment Structure Description  outer boundary of organism – very thin layer of cells Mechanism  Gasses diffuse across skin layer into the innards of the worm

Trachea Organisms  Insects Advantage  Gasses are directed to inside of body through series of smaller and smaller tubes Structure Description  meshwork of tubes running through body connected to outside of insects body Mechanism  Gasses move through tubes and diffuse either into the body or into environment

Grasshoppers

Lungs Organisms  Many land animals Advantage  eliminates one-way flow of oxygen and water loss Structure Description  series of tubes leading to grape-like clusters (alveoli) Mechanism  Gasses move into alveoli and diffuse into circulatory system

Avian Lung / Air Sac Organisms  Birds Advantage  provides a larger storage of gasses for the need of more energy – no mixing of oxygen rich and oxygen poor air Structure Description  system of air sacs and lungs Mechanism  Inhaling pulls oxygen into air sacs and exhaling puts carbon dioxide into lungs