1. Monday, September 15, 2008 HW #6: –Answer “weighing the issues” pg 162 –Answer #2, 3, 5 on pg 179 Review questions for Ch 6 due Friday

2. Energy Flow and Keystone Species Aim: How does energy move through an ecosystem? 9/15/08

3. Energy Flow in ecosystems All energy in organisms ultimately comes from the sun via photosynthesis All energy in organisms ultimately comes from the sun via photosynthesis This energy moves through the community as members feed on one another, through each trophic level This energy moves through the community as members feed on one another, through each trophic level

4. Producers Also called autotrophs Also called autotrophs Plants, cyanobacteria, and algae capture solar energy and use photosynthesis to produce sugars Plants, cyanobacteria, and algae capture solar energy and use photosynthesis to produce sugars

5. Consumers Primary consumers Primary consumers eat producers Herbivores—only eat plants Ex) deer, grasshoppers

6. Consumers cont. Secondary consumers Secondary consumers prey on primary consumers Ex) wolves, rodents, birds

7. Consumers cont. Tertiary consumers Tertiary consumers predators at higher levels Carnivores—only eat meat Hawks, owls

8. Decomposers and Detritivores Consume nonliving organic matter and recycle the energy and nutrients Consume nonliving organic matter and recycle the energy and nutrients Decomposers Decomposers Break down leaf litter to be reused by plants Break down leaf litter to be reused by plants Ex) fungi and bacteria Ex) fungi and bacteria Detritivores Detritivores Scavenge the waste products or Scavenge the waste products or dead bodies of organisms Ex) millipedes and soil insects Ex) millipedes and soil insects

11. Food Web

12. Ecological Pyramids

13. Ecological Pyramids cont. Rule of 10—each trophic level contains 10% of the energy of the trophic level below it Rule of 10—each trophic level contains 10% of the energy of the trophic level below it This means that there usually are fewer organisms at higher levels of the food chain This means that there usually are fewer organisms at higher levels of the food chain Even though predators are physically larger, the number of prey lead to a greater total biomass Even though predators are physically larger, the number of prey lead to a greater total biomass

15. Keystone species A species with a strong influence on an ecosystem A species with a strong influence on an ecosystem See figure 6.12 on pg 162

16. Keystone species cont. If you remove a keystone species, it will alter a large portion of a food web If you remove a keystone species, it will alter a large portion of a food web Often is the large secondary or tertiary consumers Often is the large secondary or tertiary consumers Ex) wolves, mountain lions, starfish, sea otters Ex) wolves, mountain lions, starfish, sea otters

17. Keystone species

18. United States History In the mid 20 th century, the US government gave bounties for the hunting of wolves and mountain lions In the mid 20 th century, the US government gave bounties for the hunting of wolves and mountain lions They were largely exterminated They were largely exterminated In their absence, deer populations rose unnaturally and have overgrazed forests In their absence, deer populations rose unnaturally and have overgrazed forests

19. Another keystone example Predatory starfish Pisaster ochraceus Predatory starfish Pisaster ochraceus When it is present, diversity is high in the tidepools When it is present, diversity is high in the tidepools When it is removed, the mussels that it eats overpopulate and diversity is low When it is removed, the mussels that it eats overpopulate and diversity is low