Unit 4 Review

1. Unit 4 Review

2. 1. Biological communities change because  limiting factors cause them to reach their carrying capacity. 2. When two different species overlap in the same biological niche, they are competing for resources. 3. The rate of growth of a natural population increases until it reaches carrying capacity.

3. 4. As resources in a population become less available, population growth slows as it approaches carrying capacity. 5. Three examples of density-independent limiting factors are earthquakes, temperature, and oxygen levels. 6) A disease resulting in the deaths of one-third of a dense population of bats in a cave would be a density dependent limiting factor.

4. 7. Habitat loss and fragmentation, exploitation, alien species invasion and co-extinction are causes for loss of biodiversity. 8. The fact that organisms are adapted to survive in particular environments helps to explain why habitat destruction accounts for most extinctions. 9. The level of biodiversity that involves a variety of habits and communities is ecosystem biodiversity.

5. 10. Biodiversity is important to ecosystems because it helps populations adapt to ecological changes. 11. The four major human causes of extinction today are hunting, destroying habitats, polluting and introducing non-native species. 12. If there were no bees what would people have to do without honey.

6. 13. Zoos, botanic gardens, and wildlife parks help save species by preserving threatened species from destruction and by participating in captive breeding programs. 14. Biodiversity impacts human health by providing medicines and food resources.

7. 15. This diagram represents a food web that might occur in a coastal region. Write a research question one might choose to explore. What would happen if all of the zooplankton were removed from the web?

8. 16. A molecule of nitrogen which you have just breathed in may have been part of a plant that lived thousands of years ago, or part of a dinosaur that lived millions of years ago. This illustrates the principle that nutrients are recycled. 17. A potato plant is exposed to carbon dioxide containing radioactive carbon for 8 hours.  After this exposure, the potato roots are found to have accumulated radioactivity. These potatoes are then fed to a pig.  Two weeks later, the pig's tissue is tested for radioactivity and is found to have a higher than normal background count. The biogeochemical cycle that is apparent from this study is the carbon cycle. 

9. 18. In the past decade, increased life expectancy has NOT been a major cause of the increase in the world's population. 19. Communities have attempted to control the size of mosquito populations to prevent the spread of certain diseases such as malaria and encephalitis. Increasing populations of native fish that feed on mosquito larvae in the swamps is a control method that would most likely cause the least ecological damage.

10. 20. Compounds containing heavy metals that are dumped into the environment can upset ecosystems because they can be toxic to the organisms in the ecosystem. The graph below shows measurements of four heavy metal concentrations taken the same site from 1972 to 1996. Write a statement that represents a valid inference concerning the levels of chrome based on information in the graph. Pollution controls may have been put into operation in 1977. OR In 1990, a new source of chrome was introduced into the tidal waters.

11. 21. Base your answer to the question on the information and on your knowledge of ecology. One reason why the passenger pigeon existed in such prodigious numbers was the lack of natural predators apart from hawks and eagles. It was, however, surprisingly vulnerable to human intervention. Each female laid only one egg a year, which made it difficult to replace any losses quickly. Only a flimsy nest was made and its habit of nesting in vast colonies and migrating in huge flocks made it very easy to attack. The birds fed mainly on acorns, chestnuts and beech nuts in the extensive woodlands of North America and so when these were steadily cut down their habitat and food supplies were reduced. Human intervention was at first relatively restrained, largely because of the limited numbers living in North America. Describe what most likely happened to the passenger pigeon. The population of passenger pigeons probably decreased when their natural food sources and their habitats were reduced.

12. 22. Burning garbage is NOT a method of source reduction. 23. The use of living microorganisms to degrade environmental pollutants is called bioremediation. 24. Use of fossil fuels by humans will likely have a future consequence of loss of natural resources.

13. 25. This graph represents the potential size (exponential) of a population based on its reproductive capacity versus the actual size (logistic) of the population. Predict why the actual population growth is less than the potential population growth. The actual population growth is less than the potential population growth due to limited resources (limiting factors).

14. 26.Read the article on the next page from the Fremont Inquirer and answer the questions below. Part A) As mentioned in the article, there are several possible explanations for the increase in mountain pine beetles. Provide one reason why fire-suppression policies lead to increased beetle activity.

16. Part B) The widespread death of trees leads to a series of changes in a forest ecosystem. Identify one physical (abiotic) change that occurs in the forest ecosystem as the result of the death of mature trees. Describe an impact of that change on the forest ecosystem.

18. Part C) As the article states, the number of managed honeybee colonies has dropped significantly over the past few decades. Describe a specific economic consequence of the collapse of the managed honeybee colonies.

19. Part D) Pollination by native insects is considered an ecosystem service. Identify a different ecosystem service and explain how that service benefits human society.