Thinking Scientifically

1. Why are true climax communities rarely reached?

2. How is the inside of the human mouth an ecosystem?

3. Some people have suggested that we “farm” the krill in Antarctica and use it to feed people who are starving elsewhere. What effects might krill farming have on the Antarctic ecosystem?

4. After fires destroyed much of Yellowstone National Park in 1988, forest managers suggested humans could help the areas recover by feeding deer, bringing in plants, and planting trees. What are some of the advantages and disadvantages of intervening in recovery from a natural disaster?

5. How is natural selection apparent in succession?

6. Identify a consumer in:

     a. a black smoker

     b. the coastline ecosystem of the Aleutian Islands

     c. the blowdown zone around Mount St. Helens

     d. an ecosystem not mentioned in the text

7. In one type of mimicry, a harmless species such as a jumping spider physically resembles a noxious species such as an aggressive type of ant. Explain why the spiders must be less abundant than the ants for this system to benefit the spiders.

Additional Questions and Terms

1. Women who have breast cancer have 35% more DDT in their blood than women of the same age who do not have breast cancer. If DDT use was stopped in 1971, how can these women have it in their tissues today?

2. The buffalo-bur is a weed that grows in overgrazed areas of Colorado and poisons livestock. Striped Colorado potato beetle larvae eat the buffalo-bur. In 1859, European settlers introduced potatoes to Colorado. As potatoes flourished, so did the beetles. The insect’s natural predators – toads, stinkbugs, birds, and snakes – could not control the beetle population. By 1874, the beetles had spread across the United States and to Europe. By 1930, potatoes all over the world were infected. Pesticides eventually controlled growth of potato beetle populations but killed other insects too. The populations that these insects controlled rose to pest levels. Using DDT also selected against sensitive strains of potato beetles, and resistant strains accumulated.