1. Life Science
Food Webs

2. food web
1. A ____________ _________ is a network of food chains that have some links in common.

3. food chain
2. Food webs are just several ________ ________ put together.

4. Competition
3. __________________ is the struggle between organisms for the same resources.

5. population
4. When one _____________ in a food web changes, all other _____________ in the food web can be affected.

6. increase
5. For example, if bobcats are removed from a forest birds, mice ,and raccoon populations would _______________.

7. reduces
6. Sometimes a single population can grow out of control. For example, a red tide is a sudden explosive growth of single-celled algae in coastal areas. The toxins produced by the algae can kill many small fish. This population change also ____________ the food available for the fish’s predators.

8. Exotic species, threaten
7. Humans can change ecosystems by introducing new species. ___________ ___________ are non-native plant and animal species that have been introduced into an environment. These plants and animals can ____________ native species.

9. declined
8. Zebra mussels were accidentally introduced into freshwater ecosystems in the U.S. When this exotic species competed for resources, many native species of mussels ______________ in number.

10. grew
9. Another example of an exotic species is the cane toad in Australia. The cane toad was introduced to help control the beetle population in Australia’s sugarcane fields. Unfortunately the solution did not work. Instead of eating the beetles, the toads ate everything else. The cane toad population _________ out of control without any predators.

11. energy pyramid
10. An _________ ___________ is a model that shows how much energy flows through the food web.

12. 10%
11. Only ________ of the energy from one level is passed on to the next level.

13. Producers, most energy
12. _____________ are at the bottom level of the energy pyramid. The bottom of the pyramid represents the largest level because it contains the most organisms and therefore contains the _______ _________.

14. greater
13. In any ecosystem, the number of producers is _________than the number of herbivores.

15. higher level
14. There are fewer number of organisms and less available energy at each ________ _________ of the pyramid.

16. Critical Thinking Snake, hawk, grasshopper, mountain lion
Which organism(s) would be affected by the removal of the shrew in the food web?  
What might happen to the population of rabbits if the mountain lion was removed from this ecosystem?
If a bacteria or fungus caused the producers in this ecosystem to die, which organisms would be immediately affected?  
Snake, hawk, grasshopper, mountain lion
The rabbit population might increase because it wouldn’t have as many predators.
All organisms would be affected, but all herbivores would be directly affected: grasshopper, squirrel, rabbit, deer