1. Respiration Answers to Guided Reading

2. 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

3. 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

4. What Is The Main Process That Drives Respiration?
DIFFUSION

5. 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

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

7. 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

8. 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)

9. 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

10. 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

11. 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

12. Water and Oxygen
Carbon Dioxide

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

14. 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

18. 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

20. 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

22. Grasshoppers

23. 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

25. 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