1 / 12

December 5, 2008

December 5, 2008. Objectives: - Discuss how different factors affect the rate of photosynthesis - Describe alternative pathways plants use to make sugars Drill: List 2 factors that can affect the rate of photosynthesis. Online Simulation.

giles
Télécharger la présentation

December 5, 2008

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. December 5, 2008 • Objectives: - Discuss how different factors affect the rate of photosynthesis - Describe alternative pathways plants use to make sugars • Drill: List 2 factors that can affect the rate of photosynthesis

  2. Online Simulation • Examined the effect of varying colors of light, light intensity, and amount of carbon dioxide on the rate of photosynthesis • Measured the number of bubbles (oxygen) after 30 seconds

  3. Factors Affecting Rate of Photosynthesis & Alternative Pathways

  4. Factors that affect photosynthesis • The rate at which plants carry out photosynthesis is affected by the plant’s environment. • Three very important factors that can affect the rate of photosynthesis: • Light intensity • Level of CO2 • Temperature

  5. Light Intensity • As the light intensity increases, the rate of photosynthesis increases, and then levels off. • Leveling off represents maximum rate of photosynthesis.

  6. Level of CO2 The Effect of the Level of Carbon Dioxide on the Rate of Photosynthesis • As the level of CO2 increases, the rate of photosynthesis increases, and then levels off. • Leveling off represents maximum rate of photosynthesis.

  7. Temperature • Initially, as temperature increases, the rate of photosynthesis increases. • The rate peaks and then starts to decreases because: • Enzymes that catalyze the reactions become ineffective. • Stomata start to close, limiting water loss and entry of carbon dioxide. The Effect Temperature on the Rate of Photosynthesis

  8. C3 Plants • REVIEW: During the Calvin cycle, CO2 is used to build sugars • C3 plants (soybeans, wheat, rice) only use the Calvin Cycle to fix CO2 • Given this name because CO2 is initially made into a three carbon compound. • These plants operate during the day

  9. Alternative Pathways • Some plants that are found in hot, dry environments have adaptations that minimize water loss while still allowing photosynthesis to take place: • C4 plants • CAM plants • They do not immediately enter into the Calvin cycle like C3 plants

  10. C4 Plants • Stomata partially closed during the day • Have a specialized pathway that captures low levels of CO2 & build 4 carbon compounds that enter the Calvin cycle • Examples: sugarcane, corn, crabgrass

  11. CAM Plants • CAM plants open stomata at night and close them during the day • Have a specialized pathway that takes in CO2 at night and makes a variety of organic acids • Then during the day, enzymes break down these organic acids, releasing CO2 that enters into the Calvin cycle • Examples: cacti and pineapples

  12. Chemosynthesis • Some bacteria that live on the floor of the ocean are autotrophs, but do not make food by photosynthesis • Use a process called chemosynthesis- the process by which energy is obtained from inorganic sources such as sulfur to make food

More Related